1 00:00:03,040 --> 00:00:05,360 Speaker 1: Welcome to stot to Blow Your Mind production of My 2 00:00:05,480 --> 00:00:14,800 Speaker 1: Heart Radio. Hey you welcome to Stuff to Blow Your Mind. 3 00:00:14,880 --> 00:00:17,560 Speaker 1: My name is Robert Lamb and I'm Joe McCormick, and 4 00:00:17,640 --> 00:00:20,200 Speaker 1: we're back with part two of our series on a 5 00:00:20,520 --> 00:00:24,920 Speaker 1: Symmetry in Life Now. In the last episode, we talked 6 00:00:24,920 --> 00:00:28,760 Speaker 1: about the concept of bilateral symmetry, where basically all of 7 00:00:28,800 --> 00:00:32,479 Speaker 1: the higher animals have body plans where the left and 8 00:00:32,520 --> 00:00:35,440 Speaker 1: the right sides are more or less a copy of 9 00:00:35,440 --> 00:00:38,920 Speaker 1: one another. In other words, along one of the three 10 00:00:38,960 --> 00:00:42,600 Speaker 1: dimensions of space, our bodies are approximately mirrored, at least 11 00:00:42,640 --> 00:00:46,599 Speaker 1: on the outside. Now. Uh, In most organisms there are 12 00:00:46,800 --> 00:00:51,120 Speaker 1: minor variations on this type of symmetry, but occasionally there 13 00:00:51,120 --> 00:00:56,440 Speaker 1: are species with isolated but radical deviations, where like one 14 00:00:56,720 --> 00:01:00,600 Speaker 1: feature on the outside of an otherwise mirror were flipped 15 00:01:00,640 --> 00:01:03,880 Speaker 1: half of the body is drastically different from what you 16 00:01:03,920 --> 00:01:06,559 Speaker 1: find on the other side. Examples that came up last 17 00:01:06,600 --> 00:01:09,680 Speaker 1: time where the tusk of the nar wall, where in 18 00:01:09,800 --> 00:01:15,560 Speaker 1: most cases it's actually the left maxillary canine tooth, So 19 00:01:15,600 --> 00:01:20,200 Speaker 1: weirds the left fang basically of this whale stabbing through 20 00:01:20,240 --> 00:01:23,200 Speaker 1: the upper lip and it becomes a single tusk. We 21 00:01:23,240 --> 00:01:26,640 Speaker 1: also talked about the blowholes and skulls of toothed whales 22 00:01:26,720 --> 00:01:29,839 Speaker 1: such as the sperm whale, where in many cases these 23 00:01:29,840 --> 00:01:34,399 Speaker 1: have developed left right mismatches that seemed to have evolved 24 00:01:34,800 --> 00:01:39,119 Speaker 1: to support the capacity for echolocation. We also talked about 25 00:01:39,120 --> 00:01:42,319 Speaker 1: the cock eyed squid, which has two extremely different eyes 26 00:01:42,480 --> 00:01:46,000 Speaker 1: for looking into extremely different worlds, one for the water above, 27 00:01:46,160 --> 00:01:49,520 Speaker 1: which is filtering sunlight, and one for the water below, 28 00:01:49,640 --> 00:01:53,480 Speaker 1: which may contain flashes of bioluminescence. And so today we 29 00:01:53,520 --> 00:01:55,480 Speaker 1: wanted to pick up the series by talking about some 30 00:01:55,560 --> 00:02:00,760 Speaker 1: more fascinating examples of lopsided animal evolution. Animal with halves 31 00:02:00,800 --> 00:02:04,280 Speaker 1: that mostly match but in one capacity or another do not, 32 00:02:04,720 --> 00:02:07,520 Speaker 1: and why that would be. Now, there are many great 33 00:02:07,560 --> 00:02:12,720 Speaker 1: examples of of asymmetrical evolution in crustations, and we may 34 00:02:12,760 --> 00:02:14,840 Speaker 1: actually save some of these for the next part in 35 00:02:14,840 --> 00:02:16,440 Speaker 1: the series. I know we're going to go to at 36 00:02:16,480 --> 00:02:19,520 Speaker 1: least three parts here, but for for today's episode, I 37 00:02:19,560 --> 00:02:22,160 Speaker 1: wanted to start by getting out the lemon and the 38 00:02:22,240 --> 00:02:26,400 Speaker 1: drawn butter, because this is an asymmetry that you don't 39 00:02:26,480 --> 00:02:30,120 Speaker 1: have to be a specialist marine biologist to notice for yourself. 40 00:02:30,520 --> 00:02:34,480 Speaker 1: If you've ever eaten or even just seen a cooked lobster. 41 00:02:35,280 --> 00:02:39,839 Speaker 1: You probably have noticed a weird mismatch between the lobsters 42 00:02:39,960 --> 00:02:45,760 Speaker 1: to clause Robert, I assume you've you've seen this for yourself, Yes, yes, Um, 43 00:02:46,080 --> 00:02:48,400 Speaker 1: they're not not as recently as you have, because I 44 00:02:48,440 --> 00:02:51,240 Speaker 1: believe this, uh, this was the inspiration for this episode, right, 45 00:02:51,280 --> 00:02:53,480 Speaker 1: you recently ate a lobster? Oh, I don't. I don't 46 00:02:53,480 --> 00:02:55,320 Speaker 1: think I even told you that, but yeah, this probably 47 00:02:55,320 --> 00:02:57,480 Speaker 1: had something to do with it. I I can't confirm 48 00:02:57,680 --> 00:03:00,919 Speaker 1: the inner workings of my subconscious mind. But not too 49 00:03:00,960 --> 00:03:02,960 Speaker 1: long ago, I was in the I was in New 50 00:03:03,040 --> 00:03:06,040 Speaker 1: England where where lobster is king. I'm not gonna do 51 00:03:06,040 --> 00:03:09,200 Speaker 1: do the accent, but lobster is king. Uh. And I did, 52 00:03:09,200 --> 00:03:12,320 Speaker 1: And I did, in fact eat a lobster. And yeah, 53 00:03:12,360 --> 00:03:15,640 Speaker 1: and I noticed stark differences between the claws, even not 54 00:03:15,760 --> 00:03:18,240 Speaker 1: just looking at them, but in my fingers, you know. 55 00:03:18,320 --> 00:03:21,480 Speaker 1: One claw was was sort of a pleasure to crack 56 00:03:21,560 --> 00:03:23,359 Speaker 1: open and get the meat out of, and the other 57 00:03:23,400 --> 00:03:27,359 Speaker 1: one when I handled the inside of the pincers, Uh, 58 00:03:27,400 --> 00:03:30,560 Speaker 1: they were much sharper and and the spines within them 59 00:03:30,600 --> 00:03:34,639 Speaker 1: were much smaller and kind of we're irritating and unpleasant 60 00:03:34,639 --> 00:03:37,680 Speaker 1: to the fingers. Fascinating. So what's going on with this 61 00:03:37,720 --> 00:03:39,720 Speaker 1: claw mismatch? Oh and by the way, we should be 62 00:03:39,720 --> 00:03:43,080 Speaker 1: clear that we're talking specifically about the American lobster or 63 00:03:43,720 --> 00:03:46,520 Speaker 1: home marus americanus. This is the lobster you find along 64 00:03:46,560 --> 00:03:50,240 Speaker 1: the northern edge of the eastern coast of North America, 65 00:03:50,320 --> 00:03:53,440 Speaker 1: so all up through like the north half of the 66 00:03:53,480 --> 00:03:56,880 Speaker 1: eastern United States and up into Canada. This is like 67 00:03:56,920 --> 00:04:00,760 Speaker 1: the red lobster lobster, the lobster from your grocery store 68 00:04:00,800 --> 00:04:02,760 Speaker 1: that has rubber bands on its claws, not like the 69 00:04:02,760 --> 00:04:06,200 Speaker 1: Caribbean lobster. Yea, not the rock lobster, though I hear 70 00:04:06,240 --> 00:04:08,720 Speaker 1: those can be good eating too, I've never had one. 71 00:04:08,760 --> 00:04:12,280 Speaker 1: But anyway, so the American lobster. Uh. So, you look 72 00:04:12,320 --> 00:04:14,880 Speaker 1: at these two claws, and what you'll notice is that 73 00:04:15,200 --> 00:04:20,880 Speaker 1: usually one claw is longer and flatter, with a longer 74 00:04:21,480 --> 00:04:23,240 Speaker 1: I don't know what the technical term for this is 75 00:04:23,279 --> 00:04:27,200 Speaker 1: the danger zone, the space between the two pincers and 76 00:04:27,279 --> 00:04:30,359 Speaker 1: the insides of the pincers. On this flatter, longer claws 77 00:04:30,360 --> 00:04:33,200 Speaker 1: seemed to be sharper, more like a kind of spiky 78 00:04:33,279 --> 00:04:37,159 Speaker 1: pair of scissors. And then the other claw is shorter 79 00:04:37,360 --> 00:04:41,520 Speaker 1: in length, but bulkier, thick with muscle, and the inside 80 00:04:41,600 --> 00:04:45,400 Speaker 1: edges of its pincers have a sort of rounder, larger 81 00:04:45,440 --> 00:04:50,719 Speaker 1: grain texture, almost pebbled, rather than with tiny spines. These 82 00:04:50,760 --> 00:04:55,160 Speaker 1: claws are commonly referred to as the cutter and the crusher, respectively. 83 00:04:55,279 --> 00:04:58,000 Speaker 1: I think the cutter is sometimes called the pincher also, 84 00:04:58,440 --> 00:05:00,479 Speaker 1: But yeah, that they are what they sound like, the 85 00:05:00,480 --> 00:05:03,120 Speaker 1: cutter and the crusher. So what's going on? Why the 86 00:05:03,200 --> 00:05:06,880 Speaker 1: two different claws on the same lobster. How does a 87 00:05:06,920 --> 00:05:09,400 Speaker 1: lobster end up with two very different claws and what 88 00:05:09,480 --> 00:05:11,839 Speaker 1: are they for? Well? To answer this question, I was 89 00:05:11,880 --> 00:05:14,760 Speaker 1: reading what I thought was a really interesting older article 90 00:05:15,240 --> 00:05:19,200 Speaker 1: in American Scientist magazine. So this is from ninety nine 91 00:05:19,680 --> 00:05:24,000 Speaker 1: by an author named C. K. Govind, who was a 92 00:05:24,040 --> 00:05:27,880 Speaker 1: professor of zoology at the University of Toronto, and it's 93 00:05:27,920 --> 00:05:31,960 Speaker 1: called a symmetry in lobster claus Seems like a lot 94 00:05:32,040 --> 00:05:37,080 Speaker 1: of Govin's research focused on crustaceans, and so Govin begins 95 00:05:37,120 --> 00:05:39,640 Speaker 1: by pointing out a number of different examples of a 96 00:05:39,760 --> 00:05:43,800 Speaker 1: symmetry and animals. He talks about lateral dominance or handedness 97 00:05:43,800 --> 00:05:47,320 Speaker 1: in humans and even mentioned I thought this was interesting. 98 00:05:47,400 --> 00:05:51,520 Speaker 1: Some in some songbirds, such as canaries, you have bilateral 99 00:05:51,600 --> 00:05:56,080 Speaker 1: asymmetry in their singing apparatus. Song production seems to be 100 00:05:56,080 --> 00:05:59,599 Speaker 1: centered on structures in the left half of the cy rinks. 101 00:06:00,120 --> 00:06:03,440 Speaker 1: And so when you see asymmetries like this, uh, you 102 00:06:03,440 --> 00:06:05,440 Speaker 1: can ask all kinds of questions about them. But one 103 00:06:05,440 --> 00:06:08,480 Speaker 1: thing is that you might just assume them to be permanent, 104 00:06:08,760 --> 00:06:13,320 Speaker 1: fixed features of anatomy, hard coded by genes and express 105 00:06:13,360 --> 00:06:17,479 Speaker 1: their early development. But it's interesting that there are some 106 00:06:17,600 --> 00:06:21,479 Speaker 1: cases where a symmetry in an animal's body seems to 107 00:06:21,520 --> 00:06:25,080 Speaker 1: be reversible. Just for one example, in some cases of 108 00:06:25,160 --> 00:06:29,000 Speaker 1: lateral dominance, damage to the dominant side of the brain 109 00:06:29,120 --> 00:06:33,000 Speaker 1: or body can cause the non dominant side to assume 110 00:06:33,200 --> 00:06:36,680 Speaker 1: some functionality previously localized to the side that has now 111 00:06:36,760 --> 00:06:40,039 Speaker 1: been incapacitated. And this can lead us to wonder how 112 00:06:40,200 --> 00:06:44,520 Speaker 1: do these asymmetries develop in the first place. So Govind 113 00:06:44,720 --> 00:06:47,240 Speaker 1: argues that by examining the lobster, and this is the 114 00:06:47,279 --> 00:06:51,560 Speaker 1: American lobster Homarus americans, we can see an example of 115 00:06:51,600 --> 00:06:56,280 Speaker 1: a symmetry emerging not purely as a result of genetic coding, 116 00:06:56,279 --> 00:06:59,799 Speaker 1: but actually as a result of how the lobster interacts 117 00:06:59,800 --> 00:07:04,480 Speaker 1: with it's with its environment during a crucial early period. Uh. 118 00:07:04,560 --> 00:07:06,400 Speaker 1: And this is what brings us back to the crusher 119 00:07:06,440 --> 00:07:09,039 Speaker 1: claw and the cutter claw. So I want to read 120 00:07:09,120 --> 00:07:14,440 Speaker 1: from Govin's introduction here quote, as any self respecting gourmet knows, 121 00:07:14,560 --> 00:07:18,360 Speaker 1: the paired claws of the American lobster have decidedly different morphologies. 122 00:07:18,920 --> 00:07:22,760 Speaker 1: One claw, called the crusher or major claw, is short, stout, 123 00:07:22,800 --> 00:07:26,480 Speaker 1: and heavy, with Moehler like teeth on its biting surface. 124 00:07:26,600 --> 00:07:29,240 Speaker 1: I think that's a good comparison, moler like teeth. It's 125 00:07:29,520 --> 00:07:32,240 Speaker 1: the pebbles are like your back teeth. It's hard to 126 00:07:32,280 --> 00:07:35,160 Speaker 1: imagine them snipping something off. Instead, it seems like they 127 00:07:35,160 --> 00:07:37,720 Speaker 1: would sort of grab hold of it and be able 128 00:07:37,720 --> 00:07:41,120 Speaker 1: to smash it real good. Yeah. When when I'm looking 129 00:07:41,120 --> 00:07:42,760 Speaker 1: at a picture of this, I can't help but imagine 130 00:07:42,760 --> 00:07:46,560 Speaker 1: the lobster putting on a puppet show with with just 131 00:07:46,720 --> 00:07:48,800 Speaker 1: its pincher and its crusher, and each of them have 132 00:07:48,880 --> 00:07:51,240 Speaker 1: you know, different characters, like like like hey on the 133 00:07:51,280 --> 00:07:54,520 Speaker 1: crutchery on the pincher, and they interact. You know. Definitely 134 00:07:54,520 --> 00:07:57,160 Speaker 1: the cutter claw has the higher voice. Yeah, let's say 135 00:07:57,200 --> 00:08:00,320 Speaker 1: if they're street fighter characters, crusher claw is zang gef 136 00:08:00,440 --> 00:08:03,840 Speaker 1: and cutter claw is is what maybe maybe im bison 137 00:08:05,480 --> 00:08:09,520 Speaker 1: longer does that cheap spinning move. Yeah, um okay, so anyway, 138 00:08:09,560 --> 00:08:11,480 Speaker 1: so that that's what that is. That that's the molar 139 00:08:11,520 --> 00:08:14,400 Speaker 1: teeth on the biting surface. But then, uh, to continue 140 00:08:14,440 --> 00:08:17,440 Speaker 1: the quote, the other called the cutter or minor claw 141 00:08:17,560 --> 00:08:20,840 Speaker 1: is long and slender with incisor like teeth, or your 142 00:08:20,880 --> 00:08:23,360 Speaker 1: incisors are your front teeth, the ones that you use 143 00:08:23,440 --> 00:08:26,920 Speaker 1: to bite off things. You know, not to mash them up, 144 00:08:26,960 --> 00:08:29,920 Speaker 1: but to to separate them from what they're originally stuck 145 00:08:29,960 --> 00:08:33,080 Speaker 1: to and pull them into your mouth there for cutting. Uh. 146 00:08:33,160 --> 00:08:36,040 Speaker 1: So what Govind writes his quote, what the gourmet might 147 00:08:36,200 --> 00:08:39,840 Speaker 1: may not know, and what lobstermen know painfully well, is 148 00:08:39,880 --> 00:08:44,200 Speaker 1: that the cutter claw can give a quick, nasty pinch. Indeed, 149 00:08:44,280 --> 00:08:47,160 Speaker 1: it's dactyl, meaning the part of the claw that moves, 150 00:08:47,280 --> 00:08:51,240 Speaker 1: the closing part can close against the opposing polyx within 151 00:08:51,320 --> 00:08:56,119 Speaker 1: twenty milliseconds, which is several times faster than any human reflex. 152 00:08:56,559 --> 00:09:00,720 Speaker 1: In contrast, the crusher claw closes very slowly, but with 153 00:09:00,840 --> 00:09:04,840 Speaker 1: enough force to crack open the shells of oysters, muscles, 154 00:09:04,840 --> 00:09:08,640 Speaker 1: and other bivalves. Uh. And it's true mollusks such as 155 00:09:08,760 --> 00:09:11,880 Speaker 1: muscles are a big source of food prey for the 156 00:09:11,920 --> 00:09:14,880 Speaker 1: American lobsters. So it crawls along the ocean floor in 157 00:09:14,880 --> 00:09:17,240 Speaker 1: its adult phase. And what does it eat. Well, it 158 00:09:17,320 --> 00:09:21,360 Speaker 1: might eat some some worms of various types and stuff, 159 00:09:21,400 --> 00:09:24,479 Speaker 1: but it's it's really going to be looking for mollusks 160 00:09:24,559 --> 00:09:26,960 Speaker 1: such as muscles. It wants to crack those shells open 161 00:09:27,200 --> 00:09:30,800 Speaker 1: and get that meat inside. Also, while we're mentioning anatomy, 162 00:09:30,840 --> 00:09:33,520 Speaker 1: I this is unrelated, but I just have to say 163 00:09:33,679 --> 00:09:36,600 Speaker 1: American lobsters do p out of their faces. You kind 164 00:09:36,600 --> 00:09:39,679 Speaker 1: of can't bring lobsters up without mentioning that they face 165 00:09:39,760 --> 00:09:43,480 Speaker 1: pe and they face peace, specifically at each other, whether 166 00:09:43,520 --> 00:09:46,280 Speaker 1: it's a mate or rival. So lobster sees another lobster, 167 00:09:46,480 --> 00:09:48,920 Speaker 1: they're probably gonna be peeing out of their faces at them. 168 00:09:49,240 --> 00:09:51,600 Speaker 1: Uh though, is best I can tell. The face peeing 169 00:09:51,800 --> 00:09:55,040 Speaker 1: is symmetrical. Okay, well that's good enough. But coming back 170 00:09:55,080 --> 00:09:57,560 Speaker 1: to the clause, So the difference in the speed of 171 00:09:57,600 --> 00:10:00,480 Speaker 1: pinching between the two claws is ev sense of an 172 00:10:00,559 --> 00:10:03,440 Speaker 1: underlying difference and not just the shape of the claw, 173 00:10:03,840 --> 00:10:08,280 Speaker 1: but it's muscular composition. These these claws have different types 174 00:10:08,320 --> 00:10:11,400 Speaker 1: of muscle in them. About nine percent of the space 175 00:10:11,440 --> 00:10:14,800 Speaker 1: of a lobster's claw is taken up by the closer muscle. 176 00:10:15,200 --> 00:10:18,320 Speaker 1: This is the muscle responsible for bringing the pincers together. 177 00:10:18,880 --> 00:10:23,040 Speaker 1: Only a relatively tiny muscle is devoted to opening the claw, 178 00:10:23,400 --> 00:10:25,600 Speaker 1: which is why a lobster might be able to pinch 179 00:10:25,679 --> 00:10:29,120 Speaker 1: with massive force, but a simple rubber band can render 180 00:10:29,160 --> 00:10:32,040 Speaker 1: its claw harmless by holding it closed. It has way 181 00:10:32,080 --> 00:10:34,880 Speaker 1: more strength for closing than it does for opening. Interacting. 182 00:10:34,960 --> 00:10:37,560 Speaker 1: That's a great point. Yeah, I didn't double check this, 183 00:10:37,640 --> 00:10:40,480 Speaker 1: but I just remembered hearing a fact that may or 184 00:10:40,480 --> 00:10:46,200 Speaker 1: may not be true about alligator and crocodilian jaws like 185 00:10:46,240 --> 00:10:48,040 Speaker 1: that when I was a kid. That you know, So 186 00:10:48,120 --> 00:10:50,680 Speaker 1: they can close their jaws with massive force, but you 187 00:10:50,679 --> 00:10:53,640 Speaker 1: can actually quite easily hold their jaws together with and 188 00:10:53,760 --> 00:10:56,080 Speaker 1: they can't open them back up. So this would be 189 00:10:56,120 --> 00:11:02,160 Speaker 1: the secret of the feet of the crocodile or alligator wrestler. Yes, okay, 190 00:11:02,280 --> 00:11:04,240 Speaker 1: Now coming back to the lobster, does that mean that 191 00:11:04,280 --> 00:11:06,760 Speaker 1: the closer muscle is the delicious part? This is like 192 00:11:06,800 --> 00:11:09,760 Speaker 1: that prize sliver of meat from the claw. Well, I 193 00:11:09,960 --> 00:11:12,880 Speaker 1: don't know about relative flavors. The closer would be the 194 00:11:12,920 --> 00:11:15,320 Speaker 1: big one, and the the opener is obviously you know, 195 00:11:15,360 --> 00:11:18,320 Speaker 1: it's like ten percent, it's like one ninth the size 196 00:11:18,320 --> 00:11:21,080 Speaker 1: of the closer muscle. So I don't know exactly what 197 00:11:21,120 --> 00:11:23,200 Speaker 1: you're getting. When you have a cooked lobster and you 198 00:11:23,240 --> 00:11:24,959 Speaker 1: pull it out of there and eat it, you're probably 199 00:11:25,000 --> 00:11:27,960 Speaker 1: some combination of the two. Well, I I guess in 200 00:11:28,000 --> 00:11:30,120 Speaker 1: my experience, like the bigger the meat you pull out 201 00:11:30,120 --> 00:11:34,880 Speaker 1: of a crustacean like the greater distance of victory. And likewise, 202 00:11:35,200 --> 00:11:38,439 Speaker 1: the more that one is picking through the crustacean with 203 00:11:39,080 --> 00:11:43,679 Speaker 1: and removing tiny slivers to consume that delicious they may be. 204 00:11:44,400 --> 00:11:46,440 Speaker 1: But the more I feel like I'm some sort of 205 00:11:47,240 --> 00:11:52,280 Speaker 1: like a creature stooped on a primordial shore scavenging pieces 206 00:11:52,320 --> 00:11:55,320 Speaker 1: from a dead animal. Getting the pieces from the tiny 207 00:11:55,400 --> 00:11:57,360 Speaker 1: legs and the tiny parts makes you feel more like 208 00:11:57,440 --> 00:12:00,679 Speaker 1: it's the road. You know, you're like looking for seeds 209 00:12:00,800 --> 00:12:02,920 Speaker 1: or something to eat, But pulling out that big piece 210 00:12:02,920 --> 00:12:05,520 Speaker 1: of claw meat you feel like a king. That's right, 211 00:12:05,920 --> 00:12:08,839 Speaker 1: that's luxury. Okay, So you got these different muscles. You 212 00:12:08,880 --> 00:12:11,880 Speaker 1: got the closer muscle, the opener muscle. What what makes 213 00:12:11,920 --> 00:12:14,880 Speaker 1: the difference in the speed of pinching between the crusher 214 00:12:14,920 --> 00:12:18,120 Speaker 1: claw and the cutter claw is the type of muscle 215 00:12:18,240 --> 00:12:21,920 Speaker 1: fiber that the closing muscle is composed of. The cutter 216 00:12:22,000 --> 00:12:26,320 Speaker 1: claw is made of about fast muscle fiber, which is 217 00:12:26,400 --> 00:12:29,440 Speaker 1: exactly what it sounds like. It's designed to move quickly 218 00:12:30,280 --> 00:12:34,200 Speaker 1: along with what Govind calls a quote small ventral band 219 00:12:34,360 --> 00:12:38,600 Speaker 1: of slow muscle, whereas the crusher claw is almost entirely 220 00:12:38,960 --> 00:12:43,200 Speaker 1: or not almost, I think is entirely a slow muscle fiber. 221 00:12:43,280 --> 00:12:46,640 Speaker 1: So it closes more slowly but can close with incredible force. 222 00:12:47,080 --> 00:12:49,880 Speaker 1: And as a result, cutter snaps fast and sharp. Crusher 223 00:12:49,880 --> 00:12:54,480 Speaker 1: closes slowly, but but it's massive. So you could compare 224 00:12:54,520 --> 00:12:58,120 Speaker 1: this to handedness in humans. But Govind notes that while 225 00:12:58,160 --> 00:13:01,600 Speaker 1: the majority of humans are right hand ended, the distribution 226 00:13:01,640 --> 00:13:05,920 Speaker 1: of claws on adult lobsters seems equally probable both ways. 227 00:13:06,000 --> 00:13:08,120 Speaker 1: It's not like the crusher claw is always on the 228 00:13:08,200 --> 00:13:11,360 Speaker 1: left side. It's it's a coin flip, which which would 229 00:13:11,440 --> 00:13:15,360 Speaker 1: mean that there's that natural selection is not pushing it 230 00:13:15,480 --> 00:13:17,559 Speaker 1: one way or the other. Right, it's not, I mean 231 00:13:17,559 --> 00:13:20,480 Speaker 1: it's pushing. It's clearly pushing. The lobsters to have two 232 00:13:20,559 --> 00:13:23,600 Speaker 1: different types of clause for the asymmetry to exist, but 233 00:13:23,679 --> 00:13:27,240 Speaker 1: it doesn't seem to matter which side is which, at 234 00:13:27,280 --> 00:13:29,880 Speaker 1: least not in a way that's universal across lobsters. It 235 00:13:29,920 --> 00:13:34,520 Speaker 1: is decided, It is decided by each individual lobster in development. 236 00:13:34,640 --> 00:13:37,600 Speaker 1: So a great question then, is, okay, if the bilateral 237 00:13:37,640 --> 00:13:41,040 Speaker 1: asymmetry is individual to each lobster and it's a random 238 00:13:41,080 --> 00:13:44,239 Speaker 1: coin flip at least from a you know, uh, statistical 239 00:13:44,240 --> 00:13:46,880 Speaker 1: point of view, what causes the change? How does the 240 00:13:47,200 --> 00:13:52,880 Speaker 1: individual lobster's body when it's growing pick which side becomes which. Well, 241 00:13:52,920 --> 00:13:56,440 Speaker 1: we can look at a lobster larval development to see this. 242 00:13:56,520 --> 00:13:58,960 Speaker 1: So when they're they're tiny little things swimming around before 243 00:13:59,000 --> 00:14:02,240 Speaker 1: they become the big ubsters we recognize. During the early 244 00:14:02,360 --> 00:14:05,760 Speaker 1: larval stages, the claws of the lobster are undifferentiated. They're 245 00:14:05,760 --> 00:14:10,040 Speaker 1: exactly the same. Both claws have what Govin calls quote 246 00:14:10,080 --> 00:14:13,920 Speaker 1: a central band of fast fibers sand which dorsally and 247 00:14:14,040 --> 00:14:19,000 Speaker 1: ventrally by slow fibers. Then during the later juvenile stages, 248 00:14:19,080 --> 00:14:21,840 Speaker 1: this would be like the fourth and fifth molting stages, 249 00:14:22,200 --> 00:14:25,120 Speaker 1: there begins to be some variability in the amount of 250 00:14:25,200 --> 00:14:28,120 Speaker 1: slow and fast fibers in each claw, but then the 251 00:14:28,200 --> 00:14:31,880 Speaker 1: changes really start to become apparent during the sixth stage 252 00:14:31,880 --> 00:14:36,080 Speaker 1: of molting, quote, when the putative crusher claw becomes slightly 253 00:14:36,160 --> 00:14:39,560 Speaker 1: shorter and stouter with a central molar like tooth, while 254 00:14:39,600 --> 00:14:42,720 Speaker 1: the punitive cutter claw remains long and slender with a 255 00:14:42,840 --> 00:14:47,240 Speaker 1: central incisor like tooth. A corresponding asymmetry in the composition 256 00:14:47,240 --> 00:14:50,080 Speaker 1: of the closer muscle also develops. The muscle of the 257 00:14:50,080 --> 00:14:54,280 Speaker 1: cutter claw gradually acquires fast fibers by transforming the slow 258 00:14:54,360 --> 00:14:57,880 Speaker 1: fibers of most of its cross sectional face. The exception 259 00:14:58,040 --> 00:15:01,320 Speaker 1: is a ventral band. The muscle the crusher claw gradually 260 00:15:01,360 --> 00:15:05,160 Speaker 1: transforms all of its fast fibers to slow fibers. In 261 00:15:05,240 --> 00:15:09,440 Speaker 1: succeeding juvenile development. The paired claws further diverge toward well 262 00:15:09,520 --> 00:15:13,480 Speaker 1: defined cutter and crusher claws. So the divergence happens sometime 263 00:15:13,520 --> 00:15:16,400 Speaker 1: in the childhood of a lobster sometime around its fourth 264 00:15:16,440 --> 00:15:19,720 Speaker 1: and fifth molting stages, and really starts to appear during 265 00:15:19,720 --> 00:15:23,760 Speaker 1: the sixth molting. But then Govin mentioned something I thought 266 00:15:23,840 --> 00:15:26,280 Speaker 1: was really intriguing and experiment going all the way back 267 00:15:26,320 --> 00:15:29,760 Speaker 1: to nineteen o eight, way back to a researcher named 268 00:15:29,880 --> 00:15:33,920 Speaker 1: Victor Emmel who found that if you remove one of 269 00:15:33,920 --> 00:15:36,800 Speaker 1: the lobster's claws during the fourth or fifth stage, so 270 00:15:36,840 --> 00:15:39,560 Speaker 1: you just pull that claw off, the claw that is 271 00:15:39,640 --> 00:15:44,160 Speaker 1: left behind, still attached to the lobster, always becomes a 272 00:15:44,200 --> 00:15:48,160 Speaker 1: crusher claw. And meanwhile, the animal regenerates a new claw 273 00:15:48,240 --> 00:15:50,560 Speaker 1: where the old one was torn off. A lot of 274 00:15:50,600 --> 00:15:53,400 Speaker 1: crustaceans can do that. It grows a new claw, and 275 00:15:53,480 --> 00:15:57,760 Speaker 1: the new claw always becomes the cutter claw. But this 276 00:15:57,840 --> 00:16:00,200 Speaker 1: only happens if you do it early. So if you 277 00:16:00,240 --> 00:16:03,080 Speaker 1: pull off a lobster's claw after the larval stage, when 278 00:16:03,120 --> 00:16:06,440 Speaker 1: it's already approaching adulthood, when the asymmetry is already beginning 279 00:16:06,480 --> 00:16:10,440 Speaker 1: to show up, the original arrangement stays intact. The claw 280 00:16:10,520 --> 00:16:14,200 Speaker 1: you pulled off will regenerate as whichever type it already was. 281 00:16:18,680 --> 00:16:22,640 Speaker 1: Thank thank so this this seems to show that claw 282 00:16:22,760 --> 00:16:26,560 Speaker 1: laterality is determined sometime during the molting stages of like 283 00:16:26,640 --> 00:16:29,760 Speaker 1: four to five, and it probably won't change after that. 284 00:16:30,240 --> 00:16:34,080 Speaker 1: So what causes asymmetry to become fixed during this stage 285 00:16:34,080 --> 00:16:38,000 Speaker 1: in a young lobster's life? And here begins a long, 286 00:16:38,400 --> 00:16:42,320 Speaker 1: twisting and to my mind fascinating journey of experiments. Trying 287 00:16:42,360 --> 00:16:45,880 Speaker 1: to pin down how this happens. Most of most of 288 00:16:45,920 --> 00:16:49,160 Speaker 1: these experiments, Govind himself was in some way directly involved in, 289 00:16:49,720 --> 00:16:52,160 Speaker 1: and for the sake of brevity, I'm gonna gloss over 290 00:16:52,200 --> 00:16:54,600 Speaker 1: some details in this section, but you can look up 291 00:16:54,600 --> 00:16:56,880 Speaker 1: the article for yourself if you want. The more zoomed 292 00:16:56,920 --> 00:17:00,520 Speaker 1: inversion with all the details and citations all try to 293 00:17:00,560 --> 00:17:03,600 Speaker 1: give a more sky sky level view. So first of all, 294 00:17:03,640 --> 00:17:06,560 Speaker 1: Govin and colleagues notice some things we already know leading 295 00:17:06,560 --> 00:17:10,440 Speaker 1: into these experiments. One is that the triggers for developing 296 00:17:10,520 --> 00:17:16,320 Speaker 1: different claws must be randomly distributed under normal conditions to 297 00:17:16,440 --> 00:17:19,600 Speaker 1: explain the random distribution of claws in the wild, but 298 00:17:20,119 --> 00:17:24,160 Speaker 1: not random once a claw is lost, and this naturally 299 00:17:24,200 --> 00:17:28,200 Speaker 1: suggested something about use the way the claw is used. 300 00:17:28,240 --> 00:17:30,720 Speaker 1: When one claw is pulled off and has to grow 301 00:17:30,760 --> 00:17:34,600 Speaker 1: back a new it isn't getting used, so the remaining 302 00:17:34,640 --> 00:17:38,520 Speaker 1: claw is getting used, And maybe it's something about getting 303 00:17:38,640 --> 00:17:42,679 Speaker 1: used more that makes a claw into a crusher. This 304 00:17:42,720 --> 00:17:45,199 Speaker 1: would align with the fact that the juvenile stage in 305 00:17:45,200 --> 00:17:49,400 Speaker 1: which the claws become asymmetrical also coincides with a change 306 00:17:49,440 --> 00:17:51,919 Speaker 1: in the lobster's lifestyle. So when the claws start to 307 00:17:51,920 --> 00:17:55,760 Speaker 1: become asymmetrical is around the time when lobsters transition from 308 00:17:55,840 --> 00:17:59,959 Speaker 1: swimming amongst the plankton to living on the ocean floor 309 00:18:00,119 --> 00:18:03,719 Speaker 1: and crawling around on the substrate and burrowing in the substrate. 310 00:18:04,760 --> 00:18:08,320 Speaker 1: The substrate meaning the stuff that lines the ocean floor. Now, 311 00:18:08,440 --> 00:18:11,359 Speaker 1: some research had been done which found that if you 312 00:18:11,400 --> 00:18:13,639 Speaker 1: take a bunch of lobsters and you raise them in 313 00:18:13,880 --> 00:18:18,680 Speaker 1: smooth plastic trays environments with no stuff to mess with 314 00:18:19,119 --> 00:18:22,399 Speaker 1: on the bottom of the water, lobsters do not, in 315 00:18:22,440 --> 00:18:27,080 Speaker 1: fact develop crusher claws at all. In smooth environments, they 316 00:18:27,160 --> 00:18:31,440 Speaker 1: just get symmetrically paired cutter claws, two cutters exactly the same. 317 00:18:32,119 --> 00:18:34,800 Speaker 1: But if you put a lobster that's already reached the 318 00:18:34,840 --> 00:18:38,240 Speaker 1: stage where it's claws split into different types into a 319 00:18:38,440 --> 00:18:41,679 Speaker 1: smooth environment, it keeps its crusher claws. So again it 320 00:18:41,720 --> 00:18:44,840 Speaker 1: gets fixed sometime early on. Alright, So it seems like 321 00:18:44,840 --> 00:18:47,600 Speaker 1: it's the environment that is key here, right, It seems 322 00:18:47,600 --> 00:18:50,480 Speaker 1: to be something about the texture of the environment at 323 00:18:50,480 --> 00:18:54,400 Speaker 1: the right stage that causes crusher claws to emerge. So 324 00:18:54,560 --> 00:18:57,880 Speaker 1: here's a new experiment. You raise lobsters in a smooth 325 00:18:57,920 --> 00:19:02,600 Speaker 1: plastic environment versus one scattered with pieces of broken oyster shells. 326 00:19:02,880 --> 00:19:06,280 Speaker 1: Does a lobster grow up differently with different distributions of 327 00:19:06,280 --> 00:19:09,879 Speaker 1: claws on on smooth plastic versus oyster chips? And the 328 00:19:09,920 --> 00:19:14,040 Speaker 1: results Where oyster shells give you normal asymmetrical lobsters with 329 00:19:14,080 --> 00:19:18,080 Speaker 1: a crusher and a cutter, the smooth no substrate gives 330 00:19:18,080 --> 00:19:22,760 Speaker 1: you a pair of identical cutters. This was fascinating to me. Okay, 331 00:19:22,800 --> 00:19:26,960 Speaker 1: so it's like what it's crawling around on determines how 332 00:19:27,000 --> 00:19:30,800 Speaker 1: its claws develop. So they wanted to refine this answer further. 333 00:19:30,960 --> 00:19:34,320 Speaker 1: Why is this is it? Is this result something about 334 00:19:34,320 --> 00:19:37,680 Speaker 1: oyster chips in particular, or could it be any substrate? 335 00:19:38,119 --> 00:19:41,440 Speaker 1: So they tried the experiment again, but instead of oyster shells, 336 00:19:41,440 --> 00:19:44,919 Speaker 1: they use different stuff. They used gravel, they used mud 337 00:19:44,920 --> 00:19:50,280 Speaker 1: with debris, and they even used tanks with plastic shirt buttons, 338 00:19:50,320 --> 00:19:53,800 Speaker 1: and all of these produced normal lobsters with one crusher, 339 00:19:53,840 --> 00:19:58,359 Speaker 1: one cutter normally randomly distributed crusher claws. And in a 340 00:19:58,440 --> 00:20:02,000 Speaker 1: control they had a flat, smooth substrate that had been 341 00:20:02,080 --> 00:20:06,200 Speaker 1: painted to look like oyster chips, but it did not 342 00:20:06,600 --> 00:20:09,000 Speaker 1: but did not have any actual stuff to crawl or 343 00:20:09,000 --> 00:20:12,679 Speaker 1: burrow around in. And this did not facilitate differentiation. So 344 00:20:12,760 --> 00:20:15,600 Speaker 1: on the one that was flat and smooth but painted, uh, 345 00:20:15,640 --> 00:20:20,440 Speaker 1: it's still produced identical symmetrical cutters. Another experiment to refine 346 00:20:20,480 --> 00:20:23,879 Speaker 1: this what about lobsters and smooth plastic trays, but putting 347 00:20:23,920 --> 00:20:27,720 Speaker 1: them together instead of by themselves. This plays on the 348 00:20:27,720 --> 00:20:30,080 Speaker 1: fact that lobsters are not very friendly to each other. 349 00:20:30,200 --> 00:20:33,720 Speaker 1: They are aggressive and tend to fight each other, and 350 00:20:33,760 --> 00:20:36,239 Speaker 1: typically when they were put in together they would they 351 00:20:36,240 --> 00:20:38,880 Speaker 1: would duel a bit, and one of the lobsters would 352 00:20:38,920 --> 00:20:42,720 Speaker 1: often get one or both claws removed in battle. Yeah, 353 00:20:42,760 --> 00:20:44,600 Speaker 1: I know this is kind of going into bug fights 354 00:20:44,680 --> 00:20:47,919 Speaker 1: territory um, but the lobster. So what they found was 355 00:20:47,960 --> 00:20:50,919 Speaker 1: the lobster with both claws left would split like in 356 00:20:50,960 --> 00:20:54,600 Speaker 1: the wild with an asymmetrical distribution with one crusher claw. 357 00:20:55,000 --> 00:20:57,520 Speaker 1: So if there is no substrate, if you don't have 358 00:20:57,560 --> 00:21:00,520 Speaker 1: any mud or oyster chips to root around in fighting, 359 00:21:00,560 --> 00:21:04,760 Speaker 1: will also do to split your claws into different types. Okay, 360 00:21:04,760 --> 00:21:07,480 Speaker 1: that this makes sense. It's about having It would seem 361 00:21:07,520 --> 00:21:09,440 Speaker 1: to have something to do with the the sorts of 362 00:21:09,840 --> 00:21:14,080 Speaker 1: things you're encountering with your claws, be it chunks of 363 00:21:14,080 --> 00:21:18,800 Speaker 1: oysters or the hard body of another lobster combatant, Right, 364 00:21:18,880 --> 00:21:21,240 Speaker 1: it seems to have something to do with doing something 365 00:21:21,320 --> 00:21:25,240 Speaker 1: with the claws that that produces one crusher of the two. 366 00:21:25,800 --> 00:21:28,000 Speaker 1: Oh and as a control, I thought this is also interesting. 367 00:21:28,000 --> 00:21:29,439 Speaker 1: They're like, well, we want to make sure it's not 368 00:21:29,520 --> 00:21:32,880 Speaker 1: just the appearance of another lobster that causes a crusher 369 00:21:32,920 --> 00:21:35,840 Speaker 1: to develop. So they tried one with a smooth container 370 00:21:35,880 --> 00:21:39,520 Speaker 1: but a mirror, So if the lobster could see its reflection, 371 00:21:39,560 --> 00:21:42,000 Speaker 1: would this make it differentiate? But noe, period, you just 372 00:21:42,080 --> 00:21:45,840 Speaker 1: got two cutters. It's got to be that tactile experience. Okay, yeah, 373 00:21:46,400 --> 00:21:48,240 Speaker 1: so so far this is all lining up with the 374 00:21:48,320 --> 00:21:52,280 Speaker 1: hypothesis that it's something about the claw getting used more 375 00:21:52,400 --> 00:21:55,760 Speaker 1: that caused them to split and one to become a crusher. Uh. 376 00:21:55,840 --> 00:21:58,399 Speaker 1: So they tried a new experiment with the hypothesis that 377 00:21:58,440 --> 00:22:00,760 Speaker 1: if you put a lobster in a no normal environment 378 00:22:00,760 --> 00:22:04,399 Speaker 1: with a substrate, but you prevent only one of a 379 00:22:04,440 --> 00:22:07,720 Speaker 1: lobster's clause from opening and closing, that's going to get 380 00:22:07,760 --> 00:22:10,200 Speaker 1: less use. That's going to turn into the cutter claw, 381 00:22:10,280 --> 00:22:13,639 Speaker 1: and the other one will become a crusher. Okay, So 382 00:22:13,680 --> 00:22:16,680 Speaker 1: they tried this with various methods such as holding one 383 00:22:16,720 --> 00:22:19,040 Speaker 1: claw shut with a rubber band or with a dab 384 00:22:19,080 --> 00:22:22,960 Speaker 1: of glue, and they found, to their surprise, this did 385 00:22:23,040 --> 00:22:26,119 Speaker 1: not produce the result they expected. They thought, if a 386 00:22:26,160 --> 00:22:28,840 Speaker 1: claw can't open and close, that the other one is 387 00:22:28,840 --> 00:22:31,480 Speaker 1: going to become the crusher. But no, Instead, with these lobsters, 388 00:22:31,760 --> 00:22:34,960 Speaker 1: you still got random lateralization. In some the right became 389 00:22:35,000 --> 00:22:37,520 Speaker 1: a crusher and some of the left became a crusher. Wow, 390 00:22:37,760 --> 00:22:40,520 Speaker 1: so it's it because that was gonna be my guest 391 00:22:40,560 --> 00:22:43,080 Speaker 1: that it depends on how on how that particular claw 392 00:22:43,240 --> 00:22:47,159 Speaker 1: is being used. But we see this, uh, this this 393 00:22:47,320 --> 00:22:51,160 Speaker 1: random distribution occurring even when that one claw is say, 394 00:22:51,359 --> 00:22:55,400 Speaker 1: rubber bandage shut. Right. So here they were like, well, 395 00:22:55,400 --> 00:22:57,639 Speaker 1: maybe has something to do with the claw being used, 396 00:22:57,680 --> 00:23:00,600 Speaker 1: but not with it being able to open clothes, and 397 00:23:00,680 --> 00:23:04,000 Speaker 1: maybe it's something else. So from here they proceeded to 398 00:23:04,080 --> 00:23:07,200 Speaker 1: a number of different anatomical experiments and to try to 399 00:23:07,280 --> 00:23:10,320 Speaker 1: quickly summarize their findings. First of all, they found if 400 00:23:10,320 --> 00:23:13,240 Speaker 1: you caught a tendon preventing only one of a lobster's 401 00:23:13,240 --> 00:23:16,480 Speaker 1: claws from opening or closing, this does stop it from 402 00:23:16,520 --> 00:23:20,879 Speaker 1: becoming a crusher, possibly by preventing fast muscle fibers from 403 00:23:20,960 --> 00:23:24,360 Speaker 1: transforming into slow muscle fibers, and the reason from this 404 00:23:25,080 --> 00:23:28,320 Speaker 1: maybe it could be a result of severing reflexive nerve 405 00:23:28,480 --> 00:23:31,480 Speaker 1: pathways in the process. So they tried to see what 406 00:23:31,560 --> 00:23:35,240 Speaker 1: happened if you sever a nerve running from the claw 407 00:23:35,359 --> 00:23:39,400 Speaker 1: to the sort of central nervous system control for the claw. Uh. 408 00:23:39,520 --> 00:23:42,320 Speaker 1: A lobster's nervous system is not exactly like ours. They 409 00:23:42,320 --> 00:23:45,159 Speaker 1: don't just have one central brain leading out to everything. 410 00:23:45,160 --> 00:23:49,520 Speaker 1: They've got ganglia, you know, the centralized nodes sort of 411 00:23:49,560 --> 00:23:51,800 Speaker 1: within the nervous system. So you would want to be 412 00:23:51,840 --> 00:23:56,440 Speaker 1: severing the reflexive fiber running from the claw to the ganglia. Unfortunately, 413 00:23:56,520 --> 00:23:59,280 Speaker 1: when they did this by severing that nerve somewhere in there, 414 00:23:59,400 --> 00:24:02,960 Speaker 1: it almost always resulted from the lobsters after they came 415 00:24:02,960 --> 00:24:06,920 Speaker 1: out of anesthesia, they would perform what's known as autotomy 416 00:24:06,960 --> 00:24:10,240 Speaker 1: on themselves. So the lobster's nerve is cut, and then 417 00:24:10,280 --> 00:24:13,480 Speaker 1: the lobster says, okay, don't need this claw anymore, and 418 00:24:13,520 --> 00:24:17,240 Speaker 1: they would sever their own arm and grow a new one. UH. 419 00:24:17,320 --> 00:24:19,919 Speaker 1: This is a standard reaction actually of crustaceans. When a 420 00:24:19,960 --> 00:24:23,080 Speaker 1: limb is trapped or damaged, they just cut it off 421 00:24:23,119 --> 00:24:25,520 Speaker 1: and grow a new one, which is a fantastic thing 422 00:24:25,520 --> 00:24:28,960 Speaker 1: to be able to do. Um And apparently severing the 423 00:24:29,040 --> 00:24:33,040 Speaker 1: nerve within the claw seemed to trigger some something in 424 00:24:33,080 --> 00:24:36,199 Speaker 1: the lobster that suggested it needed to do that. That 425 00:24:36,200 --> 00:24:39,120 Speaker 1: that that causes the behavior in the lobster that says, 426 00:24:39,160 --> 00:24:41,520 Speaker 1: something's wrong with this lamb. I'm removing it and I'll 427 00:24:41,520 --> 00:24:44,080 Speaker 1: just get a new one. Fun tie in for tomorrow's 428 00:24:44,119 --> 00:24:46,879 Speaker 1: Weird House Cinema episode. Oh brilliant. I didn't even make 429 00:24:46,880 --> 00:24:51,920 Speaker 1: that connection. Yeah. So instead, the researchers tried to incapacitate 430 00:24:52,000 --> 00:24:55,359 Speaker 1: the part of the central nervous system leading to the claw, 431 00:24:55,560 --> 00:24:59,160 Speaker 1: so incapacitating it more centrally to the body. This did 432 00:24:59,200 --> 00:25:02,159 Speaker 1: work as expect did. It did prevent the claw in 433 00:25:02,240 --> 00:25:06,359 Speaker 1: question from becoming a crusher, so it has it must 434 00:25:06,400 --> 00:25:09,960 Speaker 1: have something to do with nerve inputs from the claw 435 00:25:10,480 --> 00:25:14,680 Speaker 1: that causes the asymmetry to develop. And they tested this 436 00:25:14,760 --> 00:25:19,199 Speaker 1: with some target exercise regimes. Actually, and here I I 437 00:25:19,240 --> 00:25:21,000 Speaker 1: thought this was great. So I just wanted to read 438 00:25:21,080 --> 00:25:25,480 Speaker 1: from the article. So Govind writes, quote, in an inspired moment, 439 00:25:25,800 --> 00:25:29,480 Speaker 1: we thought of enhancing activity by exercising one of the 440 00:25:29,520 --> 00:25:33,520 Speaker 1: pared claws in a substrate free environment. The lobster was 441 00:25:33,560 --> 00:25:37,240 Speaker 1: held and its claw gently stroked with a small paint 442 00:25:37,240 --> 00:25:40,920 Speaker 1: brush so that the bristles were gripped several times during 443 00:25:40,920 --> 00:25:44,920 Speaker 1: a sixty second session. This regiment was repeated three times 444 00:25:45,000 --> 00:25:47,960 Speaker 1: daily at five hour intervals through the entire fourth and 445 00:25:48,000 --> 00:25:51,800 Speaker 1: fifth stages, remember the malting stages. Um that is, for 446 00:25:51,840 --> 00:25:54,920 Speaker 1: about a month. A control group of lobsters was reared 447 00:25:55,000 --> 00:26:00,440 Speaker 1: under identical conditions, including being handled but not exercised. While 448 00:26:00,440 --> 00:26:04,119 Speaker 1: the lobsters in the control group developed paired cutter claws, 449 00:26:04,160 --> 00:26:09,479 Speaker 1: the experimental lobsters developed a crusher on the exercised left side. 450 00:26:10,640 --> 00:26:13,159 Speaker 1: And the fact that the only perceived difference between the 451 00:26:13,160 --> 00:26:17,080 Speaker 1: two groups of lobsters was the amount of exercise strengthened 452 00:26:17,119 --> 00:26:20,480 Speaker 1: our belief that some minimal level of reflex activity in 453 00:26:20,520 --> 00:26:25,680 Speaker 1: the claw is probably needed to differentiate a crusher claw. However, 454 00:26:26,040 --> 00:26:28,320 Speaker 1: then they said, Okay, what happens if we do the 455 00:26:28,359 --> 00:26:31,399 Speaker 1: exact same thing, but we exercise both claws with the 456 00:26:31,440 --> 00:26:35,879 Speaker 1: paint brush, will this give us two crusher claws, which is, 457 00:26:35,960 --> 00:26:39,040 Speaker 1: by the way, something that we basically never find in nature. 458 00:26:39,080 --> 00:26:42,040 Speaker 1: I think they cite one example of a lobster that 459 00:26:42,160 --> 00:26:45,679 Speaker 1: had two external morphology is looking like crusher claws, but 460 00:26:45,760 --> 00:26:48,959 Speaker 1: the muscles inside did not match. So that pretty much 461 00:26:49,000 --> 00:26:51,480 Speaker 1: it never happens in nature. Uh and they found no. 462 00:26:52,000 --> 00:26:55,160 Speaker 1: In fact, their experiment could not produce two crusher claws either. 463 00:26:55,480 --> 00:26:58,399 Speaker 1: In fact, it was not only not able to produce 464 00:26:58,440 --> 00:27:02,240 Speaker 1: two crusher clause it gaven just opposite. Whereas tickling only 465 00:27:02,320 --> 00:27:04,560 Speaker 1: one claw with a paint brush and making the claw 466 00:27:04,880 --> 00:27:08,359 Speaker 1: close around the paint brush by reflex that made that 467 00:27:08,440 --> 00:27:12,040 Speaker 1: the crusher boss claw. Tickling both claws but the paint 468 00:27:12,040 --> 00:27:16,080 Speaker 1: brush equally turned the lobster into a symmetrical beast with 469 00:27:16,119 --> 00:27:20,880 Speaker 1: two identical cutter claws only so huh. So if there 470 00:27:20,920 --> 00:27:24,640 Speaker 1: are any chefs out there who believe that the crusher 471 00:27:24,680 --> 00:27:28,240 Speaker 1: claw is superior, uh and and they're looking for ways 472 00:27:28,400 --> 00:27:32,199 Speaker 1: to create the the the the pure crusher lobster, uh, 473 00:27:32,480 --> 00:27:35,960 Speaker 1: it thus far seems uh impossible to pull off. It 474 00:27:36,000 --> 00:27:39,119 Speaker 1: does not seem possible, though, though I will say this 475 00:27:39,200 --> 00:27:42,080 Speaker 1: is an older article, I've not looked into subsequent attempts 476 00:27:42,080 --> 00:27:44,560 Speaker 1: to create two crusher claw lobsters, but I doubt it. 477 00:27:44,600 --> 00:27:46,720 Speaker 1: I don't think you can do that. That's just not 478 00:27:46,840 --> 00:27:51,000 Speaker 1: part of the lobster's destiny not part of its genetic destiny. 479 00:27:51,600 --> 00:27:53,159 Speaker 1: So a lot of this seems to add up to 480 00:27:53,200 --> 00:27:58,199 Speaker 1: show that it's not just stimulation or use of a 481 00:27:58,280 --> 00:28:01,240 Speaker 1: claw that causes it to be come a crusher. But 482 00:28:01,359 --> 00:28:03,760 Speaker 1: that's something that seems to be important, is that it 483 00:28:03,920 --> 00:28:09,760 Speaker 1: is differential use, which is somehow weighed or compared internally 484 00:28:10,160 --> 00:28:13,879 Speaker 1: by the lobsters nervous system or ganglia uh, and the 485 00:28:14,000 --> 00:28:17,440 Speaker 1: side that gets more use becomes a crusher. So it's 486 00:28:17,480 --> 00:28:20,960 Speaker 1: not you can't exercise both sides and make them too crushers. 487 00:28:21,000 --> 00:28:24,440 Speaker 1: If you do them equally, you get no crushers. You've 488 00:28:24,440 --> 00:28:28,240 Speaker 1: got to get one side getting more stimulation or reflex 489 00:28:28,320 --> 00:28:32,439 Speaker 1: exercise than the other one, which suggests that there is 490 00:28:33,040 --> 00:28:35,760 Speaker 1: I don't know that there is some kind of internal 491 00:28:35,840 --> 00:28:40,120 Speaker 1: comparison module going on in the nervous system. And so 492 00:28:40,520 --> 00:28:44,200 Speaker 1: Govin concludes quote in nature, as in the laboratory, initial 493 00:28:44,360 --> 00:28:47,640 Speaker 1: use or contact of one claw with a substrate sets 494 00:28:47,680 --> 00:28:51,920 Speaker 1: in motion an increasingly greater activity on that side. The 495 00:28:52,000 --> 00:28:55,280 Speaker 1: greater neural input of that side determines in the central 496 00:28:55,280 --> 00:28:58,560 Speaker 1: nervous system it's fate as a crusher, and at the 497 00:28:58,600 --> 00:29:02,880 Speaker 1: same time inhibit the opposite side from ever becoming a crusher, 498 00:29:03,440 --> 00:29:06,560 Speaker 1: and Govin ends up using an analogy of a teeter totter. 499 00:29:07,080 --> 00:29:10,360 Speaker 1: I thought this was funny, actual illustrations of crab claws 500 00:29:10,440 --> 00:29:13,560 Speaker 1: on a playground teeter totter. So he shows, okay, you 501 00:29:13,600 --> 00:29:15,960 Speaker 1: can have you can have a balance where one side 502 00:29:16,000 --> 00:29:18,560 Speaker 1: is a crusher and one's a cutter, and so cutter 503 00:29:18,640 --> 00:29:20,680 Speaker 1: is up in the air, crusher is down. You can 504 00:29:20,720 --> 00:29:24,480 Speaker 1: have balanced with with both sides straight. You know they're 505 00:29:24,480 --> 00:29:27,200 Speaker 1: both hanging up in the air and they're both cutter claws. 506 00:29:27,240 --> 00:29:29,959 Speaker 1: But if you try to have two crusher claws, something 507 00:29:30,040 --> 00:29:32,840 Speaker 1: doesn't work there. It's like the pole in the middle 508 00:29:32,840 --> 00:29:35,720 Speaker 1: of the teeter totter will break, it won't support it. 509 00:29:36,080 --> 00:29:39,840 Speaker 1: So whatever the exact calculus of experience in the nervous 510 00:29:39,840 --> 00:29:42,719 Speaker 1: system leading to claw development, these experiments seem to make 511 00:29:42,720 --> 00:29:46,320 Speaker 1: it clear that claw asymmetry is a prime example of 512 00:29:46,320 --> 00:29:52,280 Speaker 1: what Govind calls quote experience modulating inherent programs, and this 513 00:29:52,320 --> 00:29:55,120 Speaker 1: seems to be the underlying principle behind much of how 514 00:29:55,160 --> 00:29:59,440 Speaker 1: any organisms body is formed and how it behaves, which 515 00:29:59,480 --> 00:30:02,160 Speaker 1: kind of cuts through a lot of naive all or 516 00:30:02,280 --> 00:30:05,959 Speaker 1: nothing nature nurture reasoning like much of what an animal 517 00:30:06,160 --> 00:30:10,959 Speaker 1: is is necessarily a product of both it's genetically innate 518 00:30:11,080 --> 00:30:14,200 Speaker 1: materials and programs that are the starting sort of the 519 00:30:14,240 --> 00:30:18,040 Speaker 1: building blocks, and then life itself, the experience of living 520 00:30:18,040 --> 00:30:21,280 Speaker 1: in an environment and the experiences that the organism has 521 00:30:21,720 --> 00:30:25,880 Speaker 1: those determine how those innate materials and programs are expressed, 522 00:30:26,280 --> 00:30:31,480 Speaker 1: leading to vastly different outcomes, even completely opposite outcomes, flipping 523 00:30:31,520 --> 00:30:34,560 Speaker 1: the sides on which the crusher claw exists. So in 524 00:30:34,560 --> 00:30:37,160 Speaker 1: the case of of a lobster, the metaphor is kind 525 00:30:37,160 --> 00:30:39,880 Speaker 1: of profound. You know. It starts with potential for a 526 00:30:39,920 --> 00:30:42,760 Speaker 1: crusher on the right, a crusher on the left, or 527 00:30:42,880 --> 00:30:47,000 Speaker 1: no crusher at all, but probably not two crushers, and 528 00:30:47,040 --> 00:30:51,080 Speaker 1: then eventually the fixed form of its adult body depends 529 00:30:51,280 --> 00:30:55,440 Speaker 1: on some early experience, whether and how it digs around 530 00:30:55,480 --> 00:30:59,959 Speaker 1: in oyster shell chips or even shirt buttons, some early experience, 531 00:31:00,160 --> 00:31:03,400 Speaker 1: some experience of moving one claw more than the other, 532 00:31:03,760 --> 00:31:07,719 Speaker 1: getting having some kind of sensory input causing reflexes, maybe 533 00:31:07,760 --> 00:31:12,400 Speaker 1: something that is information fed into the central ganglia through 534 00:31:12,480 --> 00:31:15,880 Speaker 1: the through the nerves and the claws determines okay, this 535 00:31:15,920 --> 00:31:18,600 Speaker 1: clause getting more used than the other one that's the 536 00:31:18,640 --> 00:31:20,480 Speaker 1: one that's going to be the crusher for the rest 537 00:31:20,480 --> 00:31:23,880 Speaker 1: of my life. Fascinating. Now. I had to look this 538 00:31:23,920 --> 00:31:25,840 Speaker 1: up real quick to see if there was any information 539 00:31:25,880 --> 00:31:30,120 Speaker 1: about the taste debate between these two claws. I did 540 00:31:30,160 --> 00:31:32,400 Speaker 1: find an article. This is a two thousand eight Associated 541 00:31:32,440 --> 00:31:36,600 Speaker 1: Press article titled the Great Lobster Debate, claus Versus Tails. 542 00:31:36,920 --> 00:31:40,760 Speaker 1: As the title implies, this is mostly about taste differences 543 00:31:40,800 --> 00:31:44,200 Speaker 1: between the clause of a lobster and the tails of 544 00:31:44,240 --> 00:31:48,760 Speaker 1: a lobster um, and it points out that that of 545 00:31:49,000 --> 00:31:53,800 Speaker 1: the two claus, the crusher claw generally is tougher than 546 00:31:53,840 --> 00:31:56,280 Speaker 1: the pinture claw. Uh, it doesn't. It doesn't get into 547 00:31:56,320 --> 00:31:58,840 Speaker 1: the taste differences between the two, but it does point 548 00:31:58,840 --> 00:32:01,440 Speaker 1: out that the tai ill, on the other hand, is 549 00:32:01,640 --> 00:32:05,480 Speaker 1: meteor and more flavorful, in part due to the fact 550 00:32:05,520 --> 00:32:07,120 Speaker 1: that or in large part due to the fact that 551 00:32:07,160 --> 00:32:09,640 Speaker 1: the tail is used more the tail muscle is used 552 00:32:09,640 --> 00:32:13,240 Speaker 1: more than the claw muscles. And this UH is cited 553 00:32:13,280 --> 00:32:16,760 Speaker 1: to Brian Beal, a lobster expert and professor at the 554 00:32:16,840 --> 00:32:21,080 Speaker 1: University of Maine. How many how many lobsters did he 555 00:32:21,120 --> 00:32:25,960 Speaker 1: have to eat for that experiment? But it does make 556 00:32:26,000 --> 00:32:28,480 Speaker 1: me think that then maybe, certainly, if you're talking about 557 00:32:28,480 --> 00:32:30,800 Speaker 1: claw versus claw, it's probably going to be a matter 558 00:32:30,840 --> 00:32:34,000 Speaker 1: of personal preference. But it could be wrong on that. 559 00:32:34,040 --> 00:32:38,880 Speaker 1: Perhaps lobster h aficionados out there have some some input 560 00:32:38,960 --> 00:32:41,400 Speaker 1: on this. Maybe there's one claw they find themselves going 561 00:32:41,440 --> 00:32:45,640 Speaker 1: to before the other. Maybe they're even certain dishes where oh, well, 562 00:32:45,680 --> 00:32:48,040 Speaker 1: you you only want to use this claw for this dish, 563 00:32:48,360 --> 00:32:50,440 Speaker 1: and then you want to save your pincher or save 564 00:32:50,520 --> 00:32:54,080 Speaker 1: your crusher for some other dish. I don't know. Well, wait, 565 00:32:54,280 --> 00:32:56,160 Speaker 1: which one did you say was the one that was 566 00:32:56,280 --> 00:32:59,880 Speaker 1: usually tougher the crush This article says the crusher claw, 567 00:33:00,240 --> 00:33:02,680 Speaker 1: the larger of the two used to crush things, generally 568 00:33:02,840 --> 00:33:06,200 Speaker 1: is tougher than the pincher claw that apart. Yeah, so 569 00:33:06,240 --> 00:33:09,239 Speaker 1: that the crusher claw is the slow muscle fiber and 570 00:33:09,360 --> 00:33:13,040 Speaker 1: the pincher is the fast muscle fiber. And I I 571 00:33:13,080 --> 00:33:15,240 Speaker 1: hesitate to say this because they may but they may 572 00:33:15,240 --> 00:33:16,960 Speaker 1: not be comparable at all. I'm not sure how the 573 00:33:16,960 --> 00:33:21,000 Speaker 1: analogy goes across different you know, file of of animal life. 574 00:33:21,040 --> 00:33:23,479 Speaker 1: But I mean, if you think about a chicken, like 575 00:33:23,560 --> 00:33:26,480 Speaker 1: the breast meat is generally the fast muscle fiber and 576 00:33:26,520 --> 00:33:28,960 Speaker 1: the dark meat is generally the slow muscle fiber, and 577 00:33:28,960 --> 00:33:32,560 Speaker 1: that translates to different types of taste and texture within 578 00:33:32,600 --> 00:33:36,040 Speaker 1: the meat. Like generally chefs would cook dark meat to 579 00:33:36,080 --> 00:33:38,480 Speaker 1: a higher temperature because it has more sort of that 580 00:33:38,560 --> 00:33:41,800 Speaker 1: needs to render out of it to render it tender. Yeah, 581 00:33:42,320 --> 00:33:46,040 Speaker 1: this this article indicates that generally speaking, your lobster tail, 582 00:33:46,240 --> 00:33:49,800 Speaker 1: that's what's gonna get like deep fried or whatever. Uh, 583 00:33:49,920 --> 00:33:52,840 Speaker 1: while the claw meat is going to be more tender, 584 00:33:52,880 --> 00:33:55,000 Speaker 1: and that's what's going to go into your lobster rolls 585 00:33:55,400 --> 00:33:59,400 Speaker 1: and your lobster club sandwiches. I'm sure there are people 586 00:33:59,440 --> 00:34:01,160 Speaker 1: who want to find about whether you're supposed to deep 587 00:34:01,160 --> 00:34:05,280 Speaker 1: fry lobster or not. We're not here to settle that debate. Um. 588 00:34:05,320 --> 00:34:08,160 Speaker 1: But anyway, I found this little research journey fascinating trying 589 00:34:08,200 --> 00:34:11,399 Speaker 1: to pin down how and why this happens in a lobster. Uh. 590 00:34:11,400 --> 00:34:15,600 Speaker 1: And it also just seems like somehow rich for metaphor. Yeah, yeah, 591 00:34:15,760 --> 00:34:18,360 Speaker 1: it's this is fascinating. I I don't know that I 592 00:34:18,360 --> 00:34:21,400 Speaker 1: had really given much thought to the same part, because 593 00:34:21,400 --> 00:34:25,560 Speaker 1: there are certainly clawed crustaceans out there that have that 594 00:34:25,640 --> 00:34:28,839 Speaker 1: are more pronounced in their asymmetry, and I think we're 595 00:34:28,840 --> 00:34:31,040 Speaker 1: gonna get into those more in the third episode in 596 00:34:31,080 --> 00:34:34,840 Speaker 1: this series. Yes, there are some crustaceans, specifically some crabs 597 00:34:34,880 --> 00:34:38,520 Speaker 1: that take claw a symmetry to a ridiculous extreme that 598 00:34:38,600 --> 00:34:47,200 Speaker 1: we'll save those for next time. Thank thank Alright, So 599 00:34:47,320 --> 00:34:50,640 Speaker 1: sticking to the the aquatic world here, I thought I'd 600 00:34:50,680 --> 00:34:53,160 Speaker 1: go in another direction that I imagine a lot of 601 00:34:53,160 --> 00:34:55,719 Speaker 1: people were thinking about as we were talking about a symmetry, 602 00:34:55,760 --> 00:34:57,719 Speaker 1: and particularly in the last episode, you know we were 603 00:34:57,719 --> 00:35:02,040 Speaker 1: talking about the blowhole of the toothed whale migrating up 604 00:35:02,080 --> 00:35:05,440 Speaker 1: to the top of the head. Well, um, we have 605 00:35:05,520 --> 00:35:08,360 Speaker 1: to talk about the flat fish. There's some eight hundred 606 00:35:08,440 --> 00:35:11,920 Speaker 1: species of flat fish and global waters, and probably the 607 00:35:11,960 --> 00:35:14,160 Speaker 1: most one of the most famous groups here is the 608 00:35:14,160 --> 00:35:17,880 Speaker 1: flounder um. And if you haven't seen a flounder, do 609 00:35:17,960 --> 00:35:20,520 Speaker 1: look up a picture. The pictures there are. A picture 610 00:35:20,520 --> 00:35:25,400 Speaker 1: of a flounder is always amusing or unsettling. Um. Basically, 611 00:35:25,440 --> 00:35:28,439 Speaker 1: what has occurred here is that the flat fish's eye 612 00:35:29,120 --> 00:35:32,200 Speaker 1: left or right, depending on the variety of fish, has 613 00:35:32,320 --> 00:35:36,000 Speaker 1: migrated to one side of its body to facilitate a 614 00:35:36,239 --> 00:35:41,360 Speaker 1: sideways life in which it camouflages itself against the ocean floor, 615 00:35:41,480 --> 00:35:44,759 Speaker 1: but like basically living on the floor, kind of like 616 00:35:45,320 --> 00:35:48,600 Speaker 1: a array or something would live on the floor, but 617 00:35:48,600 --> 00:35:54,000 Speaker 1: but it it acquires its flatness by being sideways. Both 618 00:35:54,040 --> 00:35:58,520 Speaker 1: eyes are on the side facing up. This looks hilarious, 619 00:35:58,640 --> 00:36:02,359 Speaker 1: And uh, I think it's different, unless I'm forgetting one. 620 00:36:02,440 --> 00:36:04,200 Speaker 1: I think this is different than any of the other 621 00:36:04,320 --> 00:36:08,160 Speaker 1: asymmetry examples we've talked about before, because I think all 622 00:36:08,160 --> 00:36:10,120 Speaker 1: of the other ones have been cases where there is 623 00:36:10,160 --> 00:36:14,080 Speaker 1: something that's originally symmetrical on on both sides of the body, 624 00:36:14,440 --> 00:36:17,879 Speaker 1: and then they develop in different ways like one uh 625 00:36:17,920 --> 00:36:20,600 Speaker 1: you know, maybe one hole opens and the other one closes, 626 00:36:20,680 --> 00:36:23,040 Speaker 1: or one claw grows bigger and with different shapes than 627 00:36:23,040 --> 00:36:25,440 Speaker 1: the other, different muscle fibers or something like that. They 628 00:36:25,480 --> 00:36:28,799 Speaker 1: just develop in different ways or two different extents. This 629 00:36:28,880 --> 00:36:31,680 Speaker 1: is a case of asymmetry where something that was originally 630 00:36:31,760 --> 00:36:35,600 Speaker 1: symmetrical has one of the two elements migrate to the 631 00:36:35,640 --> 00:36:40,280 Speaker 1: opposite side. Uh, so they're they're actually switching sides instead 632 00:36:40,280 --> 00:36:43,759 Speaker 1: of just like one growing bigger than the other or something. Yeah. Yeah, 633 00:36:43,920 --> 00:36:46,719 Speaker 1: it's it's super weird looking and and one of the 634 00:36:46,719 --> 00:36:49,840 Speaker 1: telling things about these fish is that you can also 635 00:36:49,960 --> 00:36:54,040 Speaker 1: look at larval flounders, for example, and see eyes on 636 00:36:54,160 --> 00:36:58,120 Speaker 1: both sides of the larva's head, so it's only as 637 00:36:58,120 --> 00:37:03,000 Speaker 1: they develop immature that the eyes move to the other side. Also, 638 00:37:03,120 --> 00:37:05,279 Speaker 1: like with some of the whale examples we were looking at, 639 00:37:05,840 --> 00:37:08,080 Speaker 1: you can look back in the fossil record and make 640 00:37:08,120 --> 00:37:11,640 Speaker 1: out a halfway point in the evolution. Particularly, you can 641 00:37:11,640 --> 00:37:14,360 Speaker 1: look at the at the fifty million year old fossil 642 00:37:14,800 --> 00:37:19,000 Speaker 1: of Amphystium, which has an eye that has migrated to 643 00:37:19,120 --> 00:37:22,600 Speaker 1: the top of the head, but no farther. Oh that's interesting, 644 00:37:22,640 --> 00:37:24,840 Speaker 1: So it would have like it's it's evolved enough that 645 00:37:24,880 --> 00:37:27,200 Speaker 1: it has one eye pointing up and another one sort 646 00:37:27,200 --> 00:37:30,799 Speaker 1: of pointing perpendicular to that right. Okay, it has not 647 00:37:31,239 --> 00:37:34,360 Speaker 1: reached its final form. I guess you would say. Um. 648 00:37:34,480 --> 00:37:37,440 Speaker 1: I was reading an article from two thousand and eight 649 00:37:37,680 --> 00:37:42,440 Speaker 1: in the journal Nature Buying Matt Friedman titled the evolutionary 650 00:37:42,440 --> 00:37:46,440 Speaker 1: origin of flatfish asymmetry, and he points out that EOC 651 00:37:46,520 --> 00:37:51,920 Speaker 1: and fossil evidence here with with Amphystium and another species, 652 00:37:52,120 --> 00:37:57,160 Speaker 1: heteronic tease, both demonstrate the intermediate form. I mean, I 653 00:37:57,239 --> 00:38:00,080 Speaker 1: guess is at right angles is better than one of 654 00:38:00,120 --> 00:38:03,560 Speaker 1: just looking down at the dirt. Yeah. Yeah, but it's 655 00:38:03,960 --> 00:38:05,960 Speaker 1: it's it's again. This one makes me think back to 656 00:38:06,080 --> 00:38:08,120 Speaker 1: the cock eyed squid. It makes me think of just 657 00:38:08,600 --> 00:38:12,880 Speaker 1: some of the strange challenges of aquatic life in general 658 00:38:13,120 --> 00:38:19,319 Speaker 1: that lead to these adjustments in a creature's form. It's it's, 659 00:38:19,360 --> 00:38:23,120 Speaker 1: it's it's so fascinating. Yeah. Yeah. And of course, well 660 00:38:23,120 --> 00:38:24,839 Speaker 1: one might ask, well, you know, why don't we see 661 00:38:24,840 --> 00:38:28,040 Speaker 1: more examples of things like this, uh, in the surface world. 662 00:38:28,000 --> 00:38:29,680 Speaker 1: And I think the answer to that is we do. 663 00:38:30,280 --> 00:38:32,640 Speaker 1: You know, we talked to maybe not in so much 664 00:38:32,680 --> 00:38:36,480 Speaker 1: in terms of of asymmetrical solutions, but in terms of 665 00:38:36,520 --> 00:38:40,080 Speaker 1: like eyes moving with the evolution of a particular species. 666 00:38:40,120 --> 00:38:42,600 Speaker 1: I mean, we talked about, uh, we've talked about in 667 00:38:42,600 --> 00:38:45,520 Speaker 1: the show, the difference between the position of eyes on 668 00:38:46,120 --> 00:38:49,319 Speaker 1: herbivore versus the eyes on a predator. You know, do 669 00:38:49,400 --> 00:38:51,279 Speaker 1: you need your eyes in a position where you can 670 00:38:51,640 --> 00:38:54,359 Speaker 1: basically see all around you as much as possible at 671 00:38:54,360 --> 00:38:56,440 Speaker 1: a given time, or do you need those things hyper 672 00:38:56,480 --> 00:38:58,800 Speaker 1: focused on the thing that it's in front of you? 673 00:38:58,800 --> 00:39:01,600 Speaker 1: You know, these are positions it, uh, that are reached 674 00:39:02,000 --> 00:39:05,719 Speaker 1: via evolution. Yeah. And actually, to take that even further though, 675 00:39:05,960 --> 00:39:07,759 Speaker 1: this has less to do with the placement of the eyes, 676 00:39:07,800 --> 00:39:10,840 Speaker 1: but more about the shapes of the actual eyeballs themselves. 677 00:39:10,840 --> 00:39:13,400 Speaker 1: You know, we talked not too long ago about research 678 00:39:13,440 --> 00:39:18,520 Speaker 1: even finding differences in common eye shapes based on whether 679 00:39:18,560 --> 00:39:21,640 Speaker 1: a predator is like, is an active predator or an 680 00:39:21,680 --> 00:39:24,520 Speaker 1: ambush predator. You know that that tends to specialize for 681 00:39:24,600 --> 00:39:26,880 Speaker 1: different types of vision, Like do you need to have 682 00:39:26,960 --> 00:39:31,120 Speaker 1: really good vision for estimating the distance needed for one 683 00:39:31,760 --> 00:39:34,280 Speaker 1: pouncing jump, or do you need the kind of vision 684 00:39:34,360 --> 00:39:39,000 Speaker 1: needed for chasing over a period of time? Yeah, yeah, exactly. 685 00:39:39,480 --> 00:39:41,160 Speaker 1: So that's a fun example that it just had to 686 00:39:41,160 --> 00:39:43,319 Speaker 1: bring up. But I have another one here, and this 687 00:39:43,360 --> 00:39:46,280 Speaker 1: is another famous example of a symmetry, and this time 688 00:39:46,600 --> 00:39:51,360 Speaker 1: this we are dealing with with surface species and surface creatures. 689 00:39:51,800 --> 00:39:54,720 Speaker 1: And it's also an interesting example because it's an example 690 00:39:54,800 --> 00:39:59,359 Speaker 1: of a symmetry leading to more asymmetry. What happens when 691 00:39:59,640 --> 00:40:05,600 Speaker 1: an a symmetrical creature is your preferred prey? Uh, perhaps 692 00:40:05,680 --> 00:40:09,040 Speaker 1: you become more asymmetrical in order to take advantage of it. 693 00:40:09,320 --> 00:40:12,640 Speaker 1: Oh that's interesting. So you you'd imagine, like I'm just 694 00:40:12,719 --> 00:40:15,120 Speaker 1: making this up, but if you're fighting some kind of 695 00:40:15,160 --> 00:40:18,000 Speaker 1: giant lobster and one of its claws is bigger and 696 00:40:18,040 --> 00:40:21,120 Speaker 1: more dangerous than the other. If over evolutionary time your 697 00:40:21,120 --> 00:40:24,600 Speaker 1: species develops I don't know, tougher skin or defenses on 698 00:40:24,719 --> 00:40:29,000 Speaker 1: the side, that's that that matches the more dangerous lobster claw. Yeah, 699 00:40:29,040 --> 00:40:32,680 Speaker 1: assuming there's some consistency in which side of the giant 700 00:40:32,760 --> 00:40:35,600 Speaker 1: lobster the money claws on, that's true. I guess if 701 00:40:35,600 --> 00:40:37,920 Speaker 1: it was the American lobster, be random. So you're just 702 00:40:38,000 --> 00:40:40,600 Speaker 1: out of luck there. Yeah, But in this case we're 703 00:40:40,640 --> 00:40:44,160 Speaker 1: dealing let's talking about the food first, we're dealing with snails, 704 00:40:44,200 --> 00:40:49,759 Speaker 1: and snails are obviously asymmetrical, possessing either clockwise or counterclockwise 705 00:40:50,000 --> 00:40:54,960 Speaker 1: spiraling shells. Uh. And as a as a side a note, 706 00:40:55,239 --> 00:40:59,680 Speaker 1: slugs are also asymmetrical. Uh. Slugs, of course are evolutionarily 707 00:40:59,680 --> 00:41:02,759 Speaker 1: speak ing. Uh. They are snails that no longer need 708 00:41:02,800 --> 00:41:05,480 Speaker 1: to carry their homes with them. Put that put that 709 00:41:05,520 --> 00:41:10,160 Speaker 1: sort of lifestyle behind them, but they really retain the asymmetry. Wow. 710 00:41:10,239 --> 00:41:12,560 Speaker 1: I did not know this. So if I understand what 711 00:41:12,640 --> 00:41:16,840 Speaker 1: you're saying that the slugs evolved from ancestral snails, they 712 00:41:16,920 --> 00:41:20,040 Speaker 1: evolved from creatures that did have shells, and they evolved 713 00:41:20,080 --> 00:41:24,799 Speaker 1: to lose them. Them. Yeah. There. We we cover this 714 00:41:24,840 --> 00:41:26,919 Speaker 1: on an old episode of Stuff to Blow your Mind 715 00:41:27,000 --> 00:41:28,680 Speaker 1: many years back, and so some of the some of 716 00:41:28,680 --> 00:41:30,840 Speaker 1: the details are a bit foggy, but yeah, this is 717 00:41:30,880 --> 00:41:34,839 Speaker 1: the basic story of slugs and snails. Um. And by 718 00:41:34,840 --> 00:41:36,600 Speaker 1: the way, if you look at a slug, you can 719 00:41:36,640 --> 00:41:40,960 Speaker 1: still you can visually mark the asymmetry if you look 720 00:41:41,000 --> 00:41:44,040 Speaker 1: for a particular it looks like a little circular feature, 721 00:41:44,120 --> 00:41:47,520 Speaker 1: a little hole or orifice on their body. That is 722 00:41:47,560 --> 00:41:50,400 Speaker 1: the Numas dome. And yeah, it's on one side as 723 00:41:50,400 --> 00:41:53,120 Speaker 1: opposed to the other. That's really cool because that's another 724 00:41:53,239 --> 00:41:56,040 Speaker 1: case where it's like, um, I don't know, you just 725 00:41:56,120 --> 00:42:00,200 Speaker 1: imagining evolution operating in a in a direction op sit 726 00:42:00,280 --> 00:42:02,640 Speaker 1: to what you would have just naively assumed. It's like, 727 00:42:02,680 --> 00:42:05,640 Speaker 1: you know, knowing that whales evolved from mammals that used 728 00:42:05,640 --> 00:42:09,440 Speaker 1: to be land walkers, you know for quadrupedal land mammals 729 00:42:10,080 --> 00:42:12,080 Speaker 1: spent more and more time and water and eventually became 730 00:42:12,120 --> 00:42:14,560 Speaker 1: fully aquatic. So here these would be not not that 731 00:42:14,680 --> 00:42:18,279 Speaker 1: slugs evolved to gain shells, but that snails evolved in 732 00:42:18,320 --> 00:42:21,200 Speaker 1: some cases to lose their shells. Yeah. I mean, like, 733 00:42:21,320 --> 00:42:23,840 Speaker 1: like we've covered time and time again, nature is flexible. 734 00:42:24,360 --> 00:42:26,880 Speaker 1: When it comes to evolution, the card is always subject 735 00:42:26,880 --> 00:42:30,680 Speaker 1: to change. The card will change. Uh uh and uh. 736 00:42:30,719 --> 00:42:35,200 Speaker 1: And it's it's it's the species that evolved themselves into 737 00:42:35,239 --> 00:42:38,480 Speaker 1: a corner sometimes that that that that find it the 738 00:42:38,480 --> 00:42:43,200 Speaker 1: hardest to survive long term. Okay, So in modern snails 739 00:42:43,280 --> 00:42:46,680 Speaker 1: and slugs, you've got this, uh, this asymmetry, you've got 740 00:42:46,960 --> 00:42:49,440 Speaker 1: some part of their biology having a kind of clockwise 741 00:42:49,520 --> 00:42:53,880 Speaker 1: or counterclockwise component. And this would of course be of 742 00:42:54,000 --> 00:42:57,720 Speaker 1: relevance to any kind of creature that interacts regularly, especially 743 00:42:57,800 --> 00:42:59,799 Speaker 1: with the snail that's got a hard external part of 744 00:42:59,800 --> 00:43:03,040 Speaker 1: this at this clockwise or counterclockwise shell. Right, And that 745 00:43:03,239 --> 00:43:06,720 Speaker 1: brings us to a species of snake known as Awasaki's 746 00:43:06,760 --> 00:43:11,160 Speaker 1: snail eader also known as Awasaki's slug snake, and these 747 00:43:11,200 --> 00:43:14,640 Speaker 1: are found in the ya Yama Islands of Japan, and 748 00:43:14,680 --> 00:43:19,879 Speaker 1: they specialize in eating snails, and they have specialized jaw 749 00:43:20,000 --> 00:43:25,279 Speaker 1: structures that enable them to prey on clockwise, spiraling or 750 00:43:25,680 --> 00:43:28,920 Speaker 1: dextral snails. However, as a result, they have a harder 751 00:43:28,960 --> 00:43:35,080 Speaker 1: time preying on counterclockwise or sinstral snails. So basically the 752 00:43:35,120 --> 00:43:38,840 Speaker 1: way this works out is the snakes mandibles have evolved 753 00:43:38,960 --> 00:43:43,799 Speaker 1: for extracting snail bodies from their shells and UH and 754 00:43:43,840 --> 00:43:47,960 Speaker 1: this evolved independently, apparently in at least three subfamilies. According 755 00:43:47,960 --> 00:43:52,480 Speaker 1: to Hosso and Hoary, writing in the Herpetological Review in 756 00:43:52,680 --> 00:43:56,760 Speaker 1: in two thousand and six, the snake inserts its mandibles 757 00:43:56,800 --> 00:44:00,840 Speaker 1: into the snails aperture and moves each man endable forward 758 00:44:00,880 --> 00:44:04,839 Speaker 1: and back to extract the body. And these two individuals, 759 00:44:05,000 --> 00:44:07,960 Speaker 1: Hosso and Horry, they've they've written several papers on the 760 00:44:08,239 --> 00:44:11,319 Speaker 1: on the snake. If you look up the Osaki snail eater, UH, 761 00:44:11,440 --> 00:44:15,120 Speaker 1: you know you'll you'll all often or always find these 762 00:44:15,160 --> 00:44:19,480 Speaker 1: researchers involved, including a two thousand seven paper titled right 763 00:44:19,480 --> 00:44:24,600 Speaker 1: handed Snakes UH Convergent evolution of asymmetry for functional specialization. 764 00:44:25,040 --> 00:44:26,720 Speaker 1: This is one where you should look up a picture 765 00:44:26,760 --> 00:44:28,880 Speaker 1: if you can. H The one I'm looking at now, 766 00:44:29,000 --> 00:44:31,640 Speaker 1: Rob that you supplied has the snake biting onto the 767 00:44:31,640 --> 00:44:34,960 Speaker 1: snail shell, and it's got its upper jaw position on 768 00:44:35,000 --> 00:44:37,239 Speaker 1: the outside of the shell, and it's lower jaw. I 769 00:44:37,280 --> 00:44:41,279 Speaker 1: guess that's the mandible reaching in underneath the tube of 770 00:44:41,320 --> 00:44:45,440 Speaker 1: the shell. So the lower jaw is what's getting inside yeah. Yeah, 771 00:44:45,840 --> 00:44:47,279 Speaker 1: it's uh, and just looking at the picture you can 772 00:44:47,320 --> 00:44:49,520 Speaker 1: be kind of hard to work out exactly what's going on. 773 00:44:49,600 --> 00:44:52,239 Speaker 1: So I wanna read a quote here from this two 774 00:44:52,239 --> 00:44:56,200 Speaker 1: thousand seven paper. They right, We found that snakes in 775 00:44:56,200 --> 00:45:01,000 Speaker 1: the subfamily Peratina, except for non snail eating specialists, have 776 00:45:01,200 --> 00:45:04,560 Speaker 1: more teeth on the right mandible than the left. In 777 00:45:04,640 --> 00:45:11,000 Speaker 1: feeding experiments, a snail eating specialist Piraeus Iwasaki, completed extracting 778 00:45:11,239 --> 00:45:16,399 Speaker 1: a dexterral soft body faster with fewer mandible retractions than 779 00:45:16,480 --> 00:45:20,760 Speaker 1: a sinstral body. The snakes failed in holding and dropped 780 00:45:20,760 --> 00:45:26,560 Speaker 1: sinstral snails more often, owing to behavioral asymmetry when striking. Wow, 781 00:45:26,600 --> 00:45:29,279 Speaker 1: so it's been preying on these snails so long that 782 00:45:29,400 --> 00:45:33,040 Speaker 1: it's specialized for for having one side of its mouth 783 00:45:33,360 --> 00:45:36,000 Speaker 1: ready to get at a certain side of the tube 784 00:45:36,120 --> 00:45:39,320 Speaker 1: of the snail's shell. And if it if it attacks 785 00:45:39,360 --> 00:45:43,040 Speaker 1: a snail of the opposite handedness and its spiral, it's 786 00:45:43,040 --> 00:45:46,279 Speaker 1: going to be at a real disadvantage. Exactly. Yeah. So 787 00:45:46,360 --> 00:45:50,239 Speaker 1: again a fascinating example of a symmetry leading to more 788 00:45:50,280 --> 00:45:53,480 Speaker 1: a symmetry in the food chain. I'm so scared that 789 00:45:53,600 --> 00:45:55,759 Speaker 1: at some point here I've I've said snail when I'm 790 00:45:55,760 --> 00:45:59,160 Speaker 1: at snake and vice versa. I apology, I apology, I 791 00:45:59,200 --> 00:46:02,759 Speaker 1: apology if I did that. So anyway, you definitely look 792 00:46:02,840 --> 00:46:05,799 Speaker 1: up images of this the snakes, especially if you find 793 00:46:05,800 --> 00:46:09,080 Speaker 1: an image of it actually feeding on a snail shell. 794 00:46:09,760 --> 00:46:12,040 Speaker 1: All right, well, we're gonna go ahead and cap this 795 00:46:12,080 --> 00:46:14,359 Speaker 1: one off right here, but we will be back. I 796 00:46:14,400 --> 00:46:17,520 Speaker 1: think it's going to be the episode after next in 797 00:46:17,560 --> 00:46:20,480 Speaker 1: which we return with part three in this series, but 798 00:46:20,560 --> 00:46:23,120 Speaker 1: there will be more creatures of note. There will be 799 00:46:23,160 --> 00:46:27,920 Speaker 1: more fascinating evolution and adaptation, and the crabs will finally 800 00:46:28,000 --> 00:46:31,000 Speaker 1: arrive on the scene, don't they always Yes, there's no 801 00:46:31,080 --> 00:46:33,480 Speaker 1: stopping them. In the meantime, if you would like to 802 00:46:33,560 --> 00:46:35,399 Speaker 1: check out other episodes of Stuff to Blow your Mind, 803 00:46:35,440 --> 00:46:40,160 Speaker 1: our core episodes publish on Tuesdays and Thursdays. UH. You 804 00:46:40,200 --> 00:46:43,480 Speaker 1: can also enjoy, if you like, our our our Listener 805 00:46:43,480 --> 00:46:46,160 Speaker 1: Mail episodes on Mondays, our short form Artifact or Monster 806 00:46:46,200 --> 00:46:49,400 Speaker 1: Fact episodes on Wednesdays and on Fridays. We set aside 807 00:46:49,400 --> 00:46:52,200 Speaker 1: most serious concerns and just talk about a weird film. 808 00:46:52,719 --> 00:46:55,680 Speaker 1: Huge thanks as always to our excellent audio producer Seth 809 00:46:55,760 --> 00:46:58,239 Speaker 1: Nicholas Johnson. If you would like to get in touch 810 00:46:58,280 --> 00:47:00,480 Speaker 1: with us with feedback on this episode or any other, 811 00:47:00,560 --> 00:47:02,680 Speaker 1: to suggest a topic for the future, or just to 812 00:47:02,680 --> 00:47:05,560 Speaker 1: say hello. You can email us at contact at stuff 813 00:47:05,600 --> 00:47:15,319 Speaker 1: to Blow your Mind dot com. Stuff to Blow Your 814 00:47:15,320 --> 00:47:18,240 Speaker 1: Mind is production of I Heart Radio. For more podcasts 815 00:47:18,280 --> 00:47:20,359 Speaker 1: for My heart Radio, visit the i heart Radio app, 816 00:47:20,520 --> 00:47:31,800 Speaker 1: Apple Podcasts, or wherever you're listening to your favorite shows. 817 00:47:24,480 --> 00:47:29,080 Speaker 1: Bo