WEBVTT - Hunters of the Dark Ocean, Part 4 0:00:03.000 --> 0:00:06.760 Welcome to Stuff to Blow Your Mind, production of iHeartRadio. 0:00:12.680 --> 0:00:14.960 Hey, welcome to you Stuff to Blow Your Mind. My 0:00:15.080 --> 0:00:16.280 name is Robert Lamb. 0:00:16.239 --> 0:00:18.640 And I am Joe McCormick, and we're back with part 0:00:18.680 --> 0:00:22.000 four in our series on predators in the deep and 0:00:22.160 --> 0:00:25.239 Dark parts of the Ocean. Now, if you're new to 0:00:25.280 --> 0:00:27.600 the show or new to the series as usual, we 0:00:27.640 --> 0:00:30.160 would recommend you go back and start with part one 0:00:30.200 --> 0:00:32.800 of the series called Hunters of the Dark Ocean Part 0:00:32.840 --> 0:00:35.839 one and listen through to catch back up and then 0:00:35.880 --> 0:00:38.559 return to meet us here once again. But also if 0:00:38.560 --> 0:00:40.480 you just want to start here, that's fine. This isn't 0:00:40.479 --> 0:00:42.879 one of those where it's absolutely crucial to take them 0:00:42.880 --> 0:00:46.560 in order. But for a brief recap of previous episodes, 0:00:47.200 --> 0:00:50.120 we talked about how the ocean can be thought of 0:00:50.240 --> 0:00:55.960 as having different environments or zones stacked vertically on one another, which, 0:00:56.040 --> 0:00:59.840 according to their depth, have different conditions. Closer to the surface, 0:00:59.840 --> 0:01:03.360 of course, there's more warmth, less pressure, more access to 0:01:03.480 --> 0:01:07.280 sunlight for phytoplankton to feast on, and thus more access 0:01:07.319 --> 0:01:09.760 to food all the way up the chain, and then 0:01:09.800 --> 0:01:13.360 as you go deeper, the waters get colder, darker, pressure, 0:01:13.440 --> 0:01:17.160 goes up, food resources become more scarce or at least 0:01:17.240 --> 0:01:20.800 less dense. And what this means is that much like 0:01:21.000 --> 0:01:25.400 how terrestrial animals are evolved to live in one type 0:01:25.400 --> 0:01:29.280 of environment and not another, marine organisms are usually adapted 0:01:29.319 --> 0:01:32.679 not just to the ocean or seawater, but to a 0:01:32.720 --> 0:01:35.080 specific zone of the ocean. So kind of like how 0:01:35.440 --> 0:01:37.600 you're not going to find jaguars living in the middle 0:01:37.640 --> 0:01:41.520 of the Sahara. You don't find the frosted flatwood salamander 0:01:41.560 --> 0:01:45.800 in the Midwest prairie. You also don't find tuna living 0:01:45.800 --> 0:01:49.760 in deep ocean trenches like eight thousand meters down. And 0:01:50.120 --> 0:01:54.560 there are some adventurous boundary crossers, but most ocean fauna 0:01:54.840 --> 0:01:58.160 are adapted to a fairly specific depth range, and the 0:01:58.200 --> 0:02:01.280 majority of those animals do live near the surface, where 0:02:01.280 --> 0:02:04.720 conditions are less extreme and resources are more plentiful. But 0:02:05.520 --> 0:02:08.360 in this series, we are interested in the creatures that 0:02:08.440 --> 0:02:11.240 can be found farther down in the darker parts of 0:02:11.280 --> 0:02:15.200 the ocean, from the sort of twilight and midnight midwaters, 0:02:15.240 --> 0:02:17.800 all the way down to the abyssal planes on the 0:02:17.840 --> 0:02:22.880 ocean floor and even further down into deep sea trenches. Specifically, 0:02:22.919 --> 0:02:27.000 we have been looking at predators in these environments now. 0:02:27.000 --> 0:02:30.400 In Part one, we talked about a recently discovered species 0:02:30.480 --> 0:02:34.760 of ghostly predatory crustacean from almost eight thousand meters down 0:02:34.840 --> 0:02:38.600 in the Atacama Trench of the Southeastern Pacific. This new 0:02:38.639 --> 0:02:41.360 species and genus was announced in a paper in November 0:02:41.400 --> 0:02:45.600 twenty twenty four, and that example sent us off examining 0:02:45.680 --> 0:02:50.360 the positively wacky body forms of crustaceans called amphipods the 0:02:50.440 --> 0:02:54.320 order to which this animal belongs, especially their deep sea varieties, 0:02:54.480 --> 0:02:58.360 some of which had major toxic jungle charisma, others were 0:02:58.400 --> 0:03:01.639 a little more like dead Dreamer in the Nightmare City, 0:03:02.560 --> 0:03:05.560 the shapes seep down from the stars, that sort of thing. 0:03:05.840 --> 0:03:10.920 We also talked about giant predatory siphonophores, extremely weird and 0:03:10.960 --> 0:03:15.040 amazing organisms that really defy our common understanding of what 0:03:15.080 --> 0:03:18.079 it means for a creature to have or be a body, 0:03:18.800 --> 0:03:23.720 and we discussed probable sightings of an unidentified predatory cephonophor 0:03:24.280 --> 0:03:28.840 in a deep ocean trench environment. In Part two, we 0:03:28.919 --> 0:03:32.400 looked at a somewhat obscure abysslefish known as the grid 0:03:32.440 --> 0:03:35.760 eye fish, which was notable to me because of its 0:03:35.800 --> 0:03:40.000 bizarre neon yellow bean shaped eye cups, and then after 0:03:40.040 --> 0:03:42.840 that we talked about a couple of cephalopods, the strawberry 0:03:42.920 --> 0:03:47.640 squid with its interesting midwater camouflage methods and a kind 0:03:47.640 --> 0:03:51.960 of bifurcated method of sight, one eye specializing in seeing 0:03:51.960 --> 0:03:55.240 shadows from above and other eye specializing in biological self 0:03:55.240 --> 0:03:58.960 illumination from below. And we also talked about oh grimpo 0:03:59.040 --> 0:04:03.960 tooth is the mbo octopus, durable little octopod who seems 0:04:03.960 --> 0:04:07.800 to have forsaken many of the biological self defense options 0:04:08.120 --> 0:04:11.880 evolved by its cephalopod kin in exchange for adapting to 0:04:11.920 --> 0:04:15.559 deeper waters where it has less pressure from its own predators. 0:04:16.080 --> 0:04:19.440 And in part three we talked about snail fishes. These 0:04:19.480 --> 0:04:21.880 are a big player, big deal in the deep ocean 0:04:22.680 --> 0:04:25.120 family of fishes that can be found in the form 0:04:25.200 --> 0:04:29.760 of many deep adapted species, including the deepest swimming fish 0:04:30.240 --> 0:04:33.839 ever convincingly documented by science, at least as of now. 0:04:34.240 --> 0:04:38.960 The deep dwelling varieties of snailfish often look like fat, slimy, pale, 0:04:39.040 --> 0:04:44.040 pink tadpoles with translucent skin. In the words of one article, 0:04:44.040 --> 0:04:48.200 we talked about guts wrapped in cellophane in my observation, 0:04:48.320 --> 0:04:51.320 kind often like a wad of sea through chewing gum 0:04:51.360 --> 0:04:54.760 with a tail, but when the angles were just right. 0:04:54.839 --> 0:04:57.400 Of course, as you pointed out, rob they can also 0:04:57.440 --> 0:05:01.440 be surprisingly cute, with kind of plaid said unassuming eye 0:05:01.440 --> 0:05:04.279 spots making them look like a creature of the hundred 0:05:04.320 --> 0:05:08.479 acre wood. Yes, yes, but one whose skin is dissolving. 0:05:09.880 --> 0:05:13.400 But despite looking either like a half dissolved a meal 0:05:13.480 --> 0:05:16.680 from RoboCop or like a cute little piglet fish, it 0:05:16.720 --> 0:05:19.800 turns out snail fishes are the top predators of many 0:05:19.839 --> 0:05:24.240 deep ocean trench environments, so they eat amphipod, scavengers and 0:05:24.360 --> 0:05:27.080 other little animal forms you find down there. They're kind 0:05:27.080 --> 0:05:29.960 of the kings and queens of the underworld. Oh and 0:05:30.000 --> 0:05:32.560 also there is good reason for suspecting there's some of 0:05:32.600 --> 0:05:35.599 the worst smelling fish on Earth. We discussed in that 0:05:35.640 --> 0:05:38.520 episode why that is likely the case. 0:05:38.920 --> 0:05:41.920 Yeah, with science, this is not just a they look smelly. 0:05:42.320 --> 0:05:45.280 In the discussion, there's actual science to back this up. 0:05:45.720 --> 0:05:49.680 After talking about snail fishes, we also looked at anglerfish, 0:05:50.000 --> 0:05:53.080 a beautiful monster of a marine predator. Actually, an anglerfish 0:05:53.400 --> 0:05:55.919 is not just one species, also a very diverse group 0:05:55.960 --> 0:05:59.680 that has a lot of different varieties, but it has 0:05:59.720 --> 0:06:03.120 its own deep adapted varieties as well. And there are 0:06:03.200 --> 0:06:07.159 so many things that make anglerfish interesting, not just how 0:06:07.640 --> 0:06:11.040 gorgeously cartoon grotesque they look, or at least in some 0:06:11.080 --> 0:06:13.120 of their forms, you know, with the jail bar teeth 0:06:13.240 --> 0:06:17.360 and the doom cute prey lure. There are also really 0:06:17.400 --> 0:06:21.359 interesting questions about their relationship with the bacteria they farm 0:06:21.440 --> 0:06:25.160 to create their glowing lure, how do they acquire these bacteria, 0:06:25.279 --> 0:06:29.040 et cetera. And also we talked about their truly amazing 0:06:29.360 --> 0:06:34.320 mating and reproduction practices, with the tiny male grafting its 0:06:34.320 --> 0:06:37.680 body onto that of the much larger female to become 0:06:37.680 --> 0:06:42.440 a kind of carry along sperm dispenser, which itself requires 0:06:42.880 --> 0:06:47.679 interesting adaptations. For example, in the anglerfish immune system, how 0:06:47.720 --> 0:06:52.800 does the anglerfish avoid rejecting the grafted male's tissue and 0:06:52.880 --> 0:06:55.719 could knowledge of this sort be used to improve outcomes 0:06:55.760 --> 0:06:59.920 for organ transplants and other related issues in human medicine. Anyway, 0:07:00.080 --> 0:07:02.400 that's all the previous episodes. Today we're back to round 0:07:02.400 --> 0:07:05.240 out the discussion of dark ocean predators with our fourth 0:07:05.240 --> 0:07:06.119 and final part. 0:07:07.240 --> 0:07:11.680 That's right now, before we jump into a full discussion 0:07:11.760 --> 0:07:14.400 on our selections. Here, I do have a quick example 0:07:14.440 --> 0:07:17.239 I want to point out because it's an extreme example 0:07:17.280 --> 0:07:21.040 of something we discussed previously. The advantage in the deep 0:07:21.160 --> 0:07:23.760 water is in the dark ocean of having an oversized 0:07:23.800 --> 0:07:27.880 stomach that allows you to consume all you can eat 0:07:28.200 --> 0:07:31.720 when a rare meal presents itself. And this brings us 0:07:31.720 --> 0:07:35.400 to the black swallower. This is the rare fish that 0:07:35.480 --> 0:07:40.800 can swallow a fish bigger than itself via distensable stomach. 0:07:41.400 --> 0:07:41.920 You might be. 0:07:41.920 --> 0:07:45.520 Tempted to imagine like a fish with a like a 0:07:45.560 --> 0:07:49.520 beer belly that is not severe enough for what can 0:07:49.560 --> 0:07:53.400 occur here. Joe I included an illustration in a photo here, 0:07:53.440 --> 0:07:56.560 and I encourage everyone out there, when it's safe to 0:07:56.560 --> 0:07:59.760 do so, look up, look up some images of the 0:07:59.760 --> 0:08:03.160 black swallow or fish, and it is. It's pretty amazing. 0:08:03.240 --> 0:08:07.280 So essentially, it has a stomach the balloons up enough 0:08:07.320 --> 0:08:10.480 to contain a fish twice its own length and ten 0:08:10.600 --> 0:08:11.760 times its own mass. 0:08:13.240 --> 0:08:16.360 It looks like a sardine with like a small mattress 0:08:16.360 --> 0:08:17.720 folded up on its stomach. 0:08:18.360 --> 0:08:21.040 If this were not actually real, it would seem grotesque 0:08:21.120 --> 0:08:24.320 enough that it had to be, you know, something out 0:08:24.320 --> 0:08:29.040 of the human imagination. It's just it looks bizarre, just 0:08:29.120 --> 0:08:32.840 this stomach stuffed with an oversized fish, a fish larger 0:08:32.840 --> 0:08:37.120 than itself. And there are various discussions in the literature 0:08:37.120 --> 0:08:39.040 of like how does it actually eat the fish? How 0:08:39.040 --> 0:08:42.400 does it like walk its jaws up the body of 0:08:42.440 --> 0:08:43.840 the fish that it is consumed. 0:08:44.520 --> 0:08:47.319 It is true, it's hard to understand how what you're 0:08:47.360 --> 0:08:49.840 looking at is real, especially and you shared a couple 0:08:49.840 --> 0:08:52.080 of images rob one is like an illustration, but the 0:08:52.120 --> 0:08:53.599 other is like a photo. 0:08:54.120 --> 0:08:55.360 Of I think. 0:08:55.679 --> 0:08:57.520 I guess one of these ate something a little too 0:08:57.559 --> 0:09:00.440 big for its own good, and it's like a much 0:09:00.600 --> 0:09:03.760 larger fish inside the smaller fish's belly. I don't understand 0:09:03.800 --> 0:09:05.720 how it got that in there, but. 0:09:06.120 --> 0:09:09.280 You are right, it is possible for these fish to 0:09:09.400 --> 0:09:13.320 eat something that's too big. And here's the crazy detail 0:09:13.360 --> 0:09:16.240 on all of that. Apparently most of the specimens of 0:09:17.240 --> 0:09:20.679 black swallower that scientists have studied, they've made their way 0:09:20.720 --> 0:09:24.240 to the surface because the fish in question apparently ate 0:09:24.280 --> 0:09:29.040 another fish too big for it to digest before decomposition 0:09:29.240 --> 0:09:32.360 set in on their meal. So, in other words, they're 0:09:32.400 --> 0:09:36.319 two large meals rotted in their giant gut before their 0:09:36.360 --> 0:09:40.360 stomach could break it down, resulting in all those decomposition 0:09:40.480 --> 0:09:44.000 gases turning the fish into a surface bound rock balloon, 0:09:44.360 --> 0:09:46.760 which just takes them out of their deep water habitat 0:09:47.200 --> 0:09:48.640 right up to the surface, killing them. 0:09:48.920 --> 0:09:49.840 Yeah. You don't want that. 0:09:50.480 --> 0:09:52.840 Yeah, So I just had to bring this one up 0:09:52.880 --> 0:09:56.800 because the deep ocean, as we discussed it, is a 0:09:56.800 --> 0:10:00.720 place sometimes of extremes, and here is an extreme example 0:10:01.960 --> 0:10:05.680 via deep water evolution of an oversized stomach to allow 0:10:06.240 --> 0:10:08.960 these individuals to eat all they can when a meal 0:10:09.000 --> 0:10:09.680 presents itself. 0:10:19.640 --> 0:10:23.400 Now, I do have a particular deep sea predatory species 0:10:23.440 --> 0:10:26.280 that I briefly want to talk about later in this episode, 0:10:26.320 --> 0:10:29.120 but before we get to that, there was something that 0:10:29.160 --> 0:10:31.880 I found really interesting, a sort of research trail I 0:10:31.920 --> 0:10:35.720 went down that I'd like to mention, and that is 0:10:35.800 --> 0:10:39.600 on the question is it just us or do fish 0:10:39.800 --> 0:10:42.240 actually get measurably. 0:10:41.640 --> 0:10:43.160 Weirder in deeper water? 0:10:44.200 --> 0:10:46.800 And I think the answer is it's not just us 0:10:47.559 --> 0:10:52.720 if you define weird as possessing more unusual and diverse 0:10:52.840 --> 0:10:59.440 body shapes. Yes, there is research suggesting that fish in deeper, 0:10:59.600 --> 0:11:05.560 darker waters tend to have more diverse distributions of body 0:11:05.640 --> 0:11:12.080 forms in other words, they're undergoing more wildly experimental evolutionary 0:11:12.120 --> 0:11:16.880 pathways than the fish in shallower, more abundant waters. Where 0:11:16.880 --> 0:11:19.640 it's not that there's no diversity. There is diversity in 0:11:19.679 --> 0:11:22.600 shallower waters, but you'll find a lot more fish there, 0:11:22.640 --> 0:11:25.599 all doing the same thing with their bodies. 0:11:25.840 --> 0:11:28.360 Whereas in the deep they're getting weirder, or in the 0:11:28.400 --> 0:11:31.600 words of David Lynch, they're becoming more pure. 0:11:33.280 --> 0:11:35.240 So this is according to a paper I was reading 0:11:35.240 --> 0:11:38.120 published in twenty twenty one in the journal Ecology Letters 0:11:38.120 --> 0:11:41.360 by Martinez at All, called the deep sea is a 0:11:41.400 --> 0:11:46.359 hot spot of fish body shape evolution, and in their abstract, 0:11:46.760 --> 0:11:50.160 the authors introduce this idea by writing, quote, deep sea 0:11:50.200 --> 0:11:53.880 fishes have long captured our imagination with striking adaptations to 0:11:53.960 --> 0:11:58.160 life in the mysterious abyss, raising the possibility that this cold, 0:11:58.480 --> 0:12:03.199 dark ocean region may be a key hub for physiological 0:12:03.280 --> 0:12:07.960 and functional diversification. We explore this idea through an analysis 0:12:08.000 --> 0:12:11.600 of body shape evolution across ocean depth zones in over 0:12:11.720 --> 0:12:16.880 three thousand species of marine teleost fishes. So what did 0:12:16.880 --> 0:12:21.000 the survey yield? Well, yes, the authors found that quote 0:12:21.200 --> 0:12:27.280 morphological disparity of marine fish body plants incrementally increases nearly 0:12:27.400 --> 0:12:32.640 two fold from ocean surface layers to the deep sea. Now, 0:12:32.679 --> 0:12:37.240 how do you measure morphological disparity that variable they're looking 0:12:37.320 --> 0:12:40.920 at there, Well, they looked at all these different species 0:12:40.960 --> 0:12:43.400 of fish, thousands of different species from different parts of 0:12:43.400 --> 0:12:47.560 the ocean, and they compared a bunch of different measures, 0:12:48.000 --> 0:12:53.400 so basic body dimensions, length, depth and width, jaw size, 0:12:53.760 --> 0:12:58.360 head size, size of what's called the caudal peduncle basically 0:12:58.440 --> 0:13:01.680 the fleshy, tapering heart of the fish leading to the 0:13:01.720 --> 0:13:06.120 tail fin kind of the bridge to the tail. And 0:13:06.280 --> 0:13:09.240 they used these measurements to create a sort of graph 0:13:09.640 --> 0:13:13.880 or morpho space for the fish found in each zone. 0:13:14.320 --> 0:13:17.560 And what they found was that in shallower waters, while 0:13:17.720 --> 0:13:22.120 there is plenty of diversity, the body forms of different 0:13:22.160 --> 0:13:26.360 fish species tend on average to be more clustered around 0:13:26.440 --> 0:13:30.600 a standard kind of optimized design. There's just a lot 0:13:30.840 --> 0:13:32.040 more sameness. 0:13:32.400 --> 0:13:32.880 Quote. 0:13:33.120 --> 0:13:36.360 Fishes in the shallow depth zone had a large overall 0:13:36.480 --> 0:13:39.359 range in body shapes, but a majority of these species 0:13:39.559 --> 0:13:43.000 were found in high density within a small region of 0:13:43.040 --> 0:13:47.360 the morphospace. These species were centered on a fusiform or 0:13:47.440 --> 0:13:54.440 spindle shaped body typified by snappers or Lutianity and Raba 0:13:54.520 --> 0:13:57.640 included a picture of a snapper for you to look 0:13:57.679 --> 0:14:00.120 at in the outline here. So this is going to 0:14:00.160 --> 0:14:04.720 be the basic body shape of the on average optimized 0:14:04.840 --> 0:14:08.080 shallow water fish. There's gonna be just a a ton 0:14:08.120 --> 0:14:10.320 of fish that are shaped basically like this. 0:14:10.960 --> 0:14:13.480 Yeah, it's a good body shape. They're not gonna shame 0:14:13.520 --> 0:14:16.160 this fish. The fish looks good, but it is very 0:14:16.160 --> 0:14:19.360 identifiable as a fish. This fish photo could be on 0:14:19.400 --> 0:14:21.400 the Wikipedia page for fish. 0:14:21.600 --> 0:14:21.800 Yeah. 0:14:21.960 --> 0:14:25.360 Yeah, yeah, it's not gonna freak anybody out. This is 0:14:25.360 --> 0:14:31.760 not suggesting deep, strange or again, in Lynch's words, purity. However, 0:14:32.080 --> 0:14:35.280 in the intermediate depth zone, so you go down below 0:14:35.400 --> 0:14:38.840 the surface area, while this body shape is still sort 0:14:38.880 --> 0:14:42.600 of found, this fusiform body shape, there is a good 0:14:42.640 --> 0:14:46.280 bit more diversity. Body forms are less clustered around this 0:14:46.440 --> 0:14:50.720 common design and more spread out on the morphospace graph. 0:14:50.920 --> 0:14:55.200 And interestingly, quote, it is at these intermediate depths that 0:14:55.280 --> 0:14:59.800 a body plan almost nonexistent in shallow waters begins to appear, 0:15:00.480 --> 0:15:05.000 and that is quote species with elongated and tapered tails. 0:15:05.800 --> 0:15:08.680 So it's interesting we've mentioned a couple of abyssle and 0:15:08.800 --> 0:15:11.680 hatelfish fish in the deepest deepest parts of the ocean, 0:15:11.680 --> 0:15:14.040 the Abyssle plains and then even deeper than the Hatele 0:15:14.160 --> 0:15:17.120 zone in the trenches, and both of these fish species 0:15:17.600 --> 0:15:20.640 tended to have something like this design they're mentioning here, 0:15:20.720 --> 0:15:26.920 elongated bodies with tapering tails. Kind of interesting. Finally, in 0:15:27.040 --> 0:15:29.800 the deepest part of the sea, the authors found the 0:15:30.000 --> 0:15:34.760 greatest diversity of body forms mapped on the morphospace, especially 0:15:34.880 --> 0:15:38.920 landing in extremes along the axis of body elongation. 0:15:39.480 --> 0:15:39.880 Quote. 0:15:40.520 --> 0:15:43.600 At one extreme are the most slender species in our 0:15:43.680 --> 0:15:47.600 data set, snipe eels, more on that in the second, 0:15:47.840 --> 0:15:51.920 and at the other are globe shaped species like oceanic 0:15:52.440 --> 0:15:56.720 angler fishes. Now, the snipe eel, that's also worth a 0:15:56.800 --> 0:15:59.280 lookup if you get a chance. It looks like a 0:15:59.440 --> 0:16:04.920 gray whip with cartoon duck lips. So at the other 0:16:05.040 --> 0:16:07.080 end of the axis, you know, we've already talked about 0:16:07.880 --> 0:16:11.240 like the very blob shaped deep ocean angler fishes, and 0:16:11.280 --> 0:16:13.800 there are more blob shaped fish you find in the 0:16:14.360 --> 0:16:17.200 deep deep water. But you also get this other extreme, 0:16:17.280 --> 0:16:20.600 the fish that are so long and thin they're like 0:16:20.640 --> 0:16:23.800 a string almost, and yet they are still fish. 0:16:23.880 --> 0:16:26.240 This is the most Pixar already fish I think I've 0:16:26.280 --> 0:16:28.520 ever seen. You can imagine just an image of this 0:16:28.600 --> 0:16:31.040 fish going out to casting directors and just saying, find 0:16:31.040 --> 0:16:34.400 me a voice for this fish. It has a lot 0:16:34.400 --> 0:16:34.920 of character. 0:16:36.000 --> 0:16:38.720 Hey, they call me slam. 0:16:38.040 --> 0:16:42.480 You know. Yeah, yeah, I can see that working. I 0:16:42.560 --> 0:16:45.880 was imagine like Emo Phillips would be good. Oh he 0:16:45.920 --> 0:16:48.760 may already play a fish and Pixar maybe maybe he's 0:16:48.760 --> 0:16:49.360 already taken. 0:16:50.040 --> 0:16:50.360 Yeah. 0:16:50.400 --> 0:16:53.480 So to make these deep evolved fish, often it seems 0:16:53.520 --> 0:16:56.080 like you could start with a snapper fish and then 0:16:56.120 --> 0:16:58.960 you either squash it into a wad you kind of 0:16:59.000 --> 0:17:02.800 bulldog scullet it, or you stretch it out into a noodle, 0:17:03.160 --> 0:17:08.400 so you've got like whips and blobs. The authors say 0:17:08.440 --> 0:17:10.960 that also in the deepest zone, you tend to find 0:17:11.040 --> 0:17:16.000 fishes with huge mouths relative to their bodies. Big mouths 0:17:16.080 --> 0:17:19.920 and strangely tapered tails like we saw with the snail fish, 0:17:19.920 --> 0:17:21.760 so it looks like a tadpole, you know, instead of 0:17:21.800 --> 0:17:24.159 spreading out like most fishtails you think of, it just 0:17:24.200 --> 0:17:27.600 kind of tapers off to a little pencil tail. So 0:17:27.920 --> 0:17:31.720 there is a huge difference here, essentially double the evolution 0:17:31.960 --> 0:17:35.080 of disparate fish body forms in the deep zone compared 0:17:35.119 --> 0:17:37.480 to the near surface zone, where you just see a 0:17:37.520 --> 0:17:42.880 lot more species with similar body forms. What explains this well, 0:17:42.920 --> 0:17:46.640 The authors have some ideas, and those ideas come back 0:17:46.680 --> 0:17:49.560 to something we've touched on already in earlier parts of 0:17:49.600 --> 0:17:55.960 this series, the interaction between light conditions and predation. So 0:17:56.080 --> 0:18:00.240 in the photic zone of the ocean, where sunlight penetrates 0:18:00.280 --> 0:18:03.520 the water, the authors talk about how there is a 0:18:03.600 --> 0:18:08.280 lot of hunting by sight. Predators can see prey and 0:18:08.400 --> 0:18:12.040 vice versa. Pray can see predators at a relatively long distance. 0:18:12.560 --> 0:18:16.320 So there is predator and prey, you know, awareness of 0:18:16.359 --> 0:18:21.280 each other with significant distance in between. And it seems 0:18:21.320 --> 0:18:24.400 like when predators and prey can see each other at 0:18:24.400 --> 0:18:28.400 a distance, it gives rise to these kind of recurring 0:18:28.520 --> 0:18:34.520 predation patterns, things like stalking and chasing. Survival often becomes 0:18:34.560 --> 0:18:39.440 a literal race, where like swimming speed and maneuverability are 0:18:39.480 --> 0:18:42.720 the key factors that determine whether you live or die. 0:18:43.160 --> 0:18:47.800 So there's an arms race based around swimming speed. And 0:18:47.920 --> 0:18:49.600 I don't know if this is a good analogy. The 0:18:49.640 --> 0:18:51.879 authors don't make it themselves, but it also made me 0:18:51.920 --> 0:18:54.600 think about how it seems to me that there is 0:18:55.280 --> 0:18:59.600 a lot of evolutionary pressure for like quadrupedal mammals to 0:19:00.119 --> 0:19:03.200 specialized for speed when they live in very open environment, 0:19:03.320 --> 0:19:07.919 something of like the savannah right right where you sightlines 0:19:07.960 --> 0:19:11.480 are long. So the snapper form that we talked about 0:19:11.560 --> 0:19:15.360 that is so common in shallower waters maybe just kind 0:19:15.400 --> 0:19:20.840 of an optimized evolutionary design for the light drenched environment 0:19:20.920 --> 0:19:24.760 that leads to this arms race on swimming and the 0:19:24.800 --> 0:19:28.000 authors so that's one part of it, the main predation 0:19:28.240 --> 0:19:31.919 interactions predator prey interactions based on light. Also, though they 0:19:32.000 --> 0:19:37.560 point out that shallow water fish face physical environmental pressures 0:19:37.640 --> 0:19:40.840 that deep water fish usually do not face, and there 0:19:40.840 --> 0:19:42.960 are actually a lot of different things to consider here. 0:19:43.359 --> 0:19:45.560 So near the surface, you're going to have like surface 0:19:45.760 --> 0:19:50.560 weather effects and turbulent waters and more variable current that 0:19:50.640 --> 0:19:54.840 you might need to fight against, fighting against unpredictably flowing water. 0:19:56.000 --> 0:19:59.600 And also if fish live in coastal environments or along 0:19:59.680 --> 0:20:03.399 rocky seafloors, they might be needing to have ways of 0:20:03.440 --> 0:20:08.240 dealing with those environments, like rocky bottoms or reefs, maybe 0:20:08.920 --> 0:20:12.720 ways of hiding and getting around in those places. Those 0:20:12.760 --> 0:20:16.679 just create all different kinds of new evolutionary pressures. The 0:20:16.760 --> 0:20:18.960 conditions in the deep ocean, on the other hand, are 0:20:19.040 --> 0:20:21.560 relatively stable. You're not going to be fighting with a 0:20:21.600 --> 0:20:27.480 lot of weather or current or you know, like there's 0:20:27.520 --> 0:20:29.919 not a lot of different stuff going on. There's going 0:20:29.960 --> 0:20:33.360 to be a lot of floating or sitting and scuttling 0:20:33.400 --> 0:20:36.000 around along the kind of sedimented bottom. 0:20:36.119 --> 0:20:39.200 Yeah, which is We touched briefly on this with the siphonophores, 0:20:39.280 --> 0:20:41.680 mentioning that like some of the siphonophores are rather delicate 0:20:42.880 --> 0:20:45.800 in their their body structure, but they're in an area 0:20:45.840 --> 0:20:48.280 where they're not having to deal with currents and so forth, 0:20:48.320 --> 0:20:52.400 they can just live free and weird like that exactly. 0:20:52.480 --> 0:20:56.360 But also coming back to the thing about light allowing 0:20:56.359 --> 0:20:58.840 predators and prey to see one another at a distance 0:20:58.920 --> 0:21:03.560 and putting this pressure on chasing and maneuvering, the authors 0:21:03.600 --> 0:21:05.719 say that, you know, in the deepest parts of the ocean, 0:21:06.280 --> 0:21:10.159 it's kind of like the information horizon of death or 0:21:10.200 --> 0:21:10.879 of getting. 0:21:10.640 --> 0:21:12.199 A meal is much shorter. 0:21:13.119 --> 0:21:17.560 Like fish and prey, the predators in prey don't see 0:21:17.560 --> 0:21:20.399 each other at a distance. They're much more likely to 0:21:20.600 --> 0:21:24.400 just kind of bump into each other quite suddenly. Predation 0:21:24.560 --> 0:21:28.639 happens quickly in close quarters. And that's kind of interesting 0:21:28.680 --> 0:21:33.120 because it seems that this change in light conditions and 0:21:33.200 --> 0:21:37.600 the relatively short information horizon on which you can detect 0:21:37.680 --> 0:21:40.880 the presence of a predator or prey animal, it kind 0:21:40.920 --> 0:21:47.159 of relieves the otherwise overwhelming evolutionary pressure on swimming power 0:21:47.400 --> 0:21:52.520 like speed and maneuverability, and it allows deep adapted species 0:21:52.960 --> 0:21:58.040 to run weird experiments in survival, for example, by favoring 0:21:58.080 --> 0:22:03.040 body types that swim relatively slowly but can serve metabolic 0:22:03.200 --> 0:22:07.680 energy or specialize in surviving in extremely high pressure and 0:22:07.720 --> 0:22:12.000 low temperature environments. And the authors point out that this 0:22:12.080 --> 0:22:15.679 explanation is supported by the observation that many deep dwelling 0:22:15.720 --> 0:22:19.359 species of fish have kind of weak muscles. They have 0:22:19.480 --> 0:22:23.960 like low density or what are called watery muscles, which 0:22:24.119 --> 0:22:28.000 does probably make them weaker or slower swimmers, but it 0:22:28.040 --> 0:22:32.399 also helps in other ways. It helps them maintain neutral buoyancy, 0:22:32.560 --> 0:22:35.720 so that's the ability to neither float up nor sink, 0:22:35.880 --> 0:22:37.480 just kind of sit right where you are in the 0:22:37.480 --> 0:22:42.400 water column. They also point out that the extreme hydrostatic 0:22:42.440 --> 0:22:47.960 pressure of the deep ocean may actually make efficient swimming easier. 0:22:48.920 --> 0:22:53.960 Quote in laboratory settings. European eels experienced approximately sixty percent 0:22:54.160 --> 0:22:59.160 lower cost of transport under high pressure conditions. Elevated rates 0:22:59.160 --> 0:23:02.440 of evolution for locomotor traits in the deep ocean may 0:23:02.480 --> 0:23:08.080 therefore reflect the relaxation of strong selection for some aspects 0:23:08.080 --> 0:23:12.879 of locomotive performance, such as maneuverability and high speed cruising. 0:23:13.560 --> 0:23:17.119 So I thought this was interesting because it seems like, ironically, 0:23:17.440 --> 0:23:21.920 these extreme conditions in the deep ocean allow for more 0:23:22.080 --> 0:23:26.800 biological diversity and less grouping around these body shapes that 0:23:26.840 --> 0:23:29.760 get used over and over. It's sort of the opposite 0:23:29.760 --> 0:23:31.360 of what you would think. You would kind of think 0:23:31.440 --> 0:23:35.760 that the extreme environments would tend to force a lot 0:23:35.800 --> 0:23:39.040 of like a much narrower range of what could survive there, 0:23:39.040 --> 0:23:42.240 and instead it proves to be a kind of experiment 0:23:42.480 --> 0:23:46.920 kind of free experimentation space for evolution. And so that's interesting. 0:23:47.080 --> 0:23:48.440 Maybe I want to come back to that in a minute. 0:23:48.480 --> 0:23:51.400 But there are also it's worth pointing out there are 0:23:51.440 --> 0:23:55.040 a few things about the deep ocean that might be 0:23:55.119 --> 0:23:58.960 thought of as analogous to the pressure on swimming speed 0:23:58.960 --> 0:24:02.720 and maneuverability in the shallow ocean. One thing is the 0:24:02.840 --> 0:24:06.560 overwhelming pressure to not miss out on a chance to eat, 0:24:07.119 --> 0:24:10.840 and that leads to one thing that they found, a 0:24:10.880 --> 0:24:15.360 thing that's not variable. Among deep sea fishes, they almost 0:24:15.440 --> 0:24:20.199 all seem to have big mouths, specifically long jaws. This 0:24:20.280 --> 0:24:24.200 goes back to your black swallower example. In that example, 0:24:24.240 --> 0:24:26.640 it was the stomach, though I suspect it probably also 0:24:26.760 --> 0:24:31.560 has relatively large jaws compared to fish of its size 0:24:32.240 --> 0:24:35.720 throughout the ocean. But the thinking here is that the 0:24:35.760 --> 0:24:39.360 big mouths, the long jaws is about resource scarcity, kind 0:24:39.359 --> 0:24:42.800