WEBVTT - From the Vault: The Parrotfish, Part 2 0:00:06.160 --> 0:00:08.760 Hey, welcome to Stuff to Blow your Mind. It is 0:00:08.800 --> 0:00:11.280 another Vault day here for you. So we have the 0:00:11.320 --> 0:00:16.160 Parrotfish Part two. It originally published five three, twenty twenty four. 0:00:16.440 --> 0:00:19.720 I hope you enjoy. 0:00:20.520 --> 0:00:24.600 Welcome to Stuff to Blow Your Mind production of iHeartRadio. 0:00:30.360 --> 0:00:32.560 Hey, welcome to Stuff to Blow your Mind. My name 0:00:32.600 --> 0:00:33.640 is Robert Lamb. 0:00:33.600 --> 0:00:36.000 And I am Joe McCormick, and we're back with Part 0:00:36.040 --> 0:00:40.160 two in our series on parrotfish, a group of related 0:00:40.240 --> 0:00:44.879 fishes containing about ninety to one hundred species worldwide, notable 0:00:45.000 --> 0:00:48.839 for their powerful beak like mouths made out of rows 0:00:48.840 --> 0:00:53.600 of fused teeth. In the previous episode, we talked about 0:00:53.640 --> 0:00:57.680 some basics about the biology and taxonomy of parrotfish species. 0:00:58.200 --> 0:01:01.960 We talked about their diet and feeding behavior. Parrot Fish 0:01:01.960 --> 0:01:06.520 are usually considered herbivores or something equivalent to herbivores. They 0:01:06.560 --> 0:01:11.040 survive by grazing for algae, microorganisms, to trite us, and 0:01:11.080 --> 0:01:15.399 sometimes invertebrate animals like coral polyps along the surfaces of 0:01:15.560 --> 0:01:20.400 rocks and coral skeletons within coral reef environments. We talked 0:01:20.480 --> 0:01:24.280 about the fact that some parrotfish species end up biting 0:01:24.600 --> 0:01:28.959 or scraping off significant chunks of hard matter from the 0:01:29.080 --> 0:01:31.960 rocks and coral that they scour for food, and then 0:01:32.080 --> 0:01:37.440 grinding up these coral skeletons and minerals in their phryngial mills. 0:01:37.680 --> 0:01:40.720 It's kind of like horror movie machinery in the back 0:01:40.760 --> 0:01:42.560 of their throats. I think we compared it to like 0:01:42.600 --> 0:01:47.200 a bone transmission gear and then defecating what's left in 0:01:47.240 --> 0:01:50.240 the form of sand. And so as a result, parrotfish 0:01:50.280 --> 0:01:53.440 are major figures in the erosion of coral reefs and 0:01:53.520 --> 0:01:56.240 in the production of sand. So if you walk across 0:01:56.320 --> 0:01:59.240 a white sandy beach in the tropics where there are 0:01:59.240 --> 0:02:02.320 coral reefs nearby, there is a good chance that most 0:02:02.400 --> 0:02:05.279 of the sand under your feet was at one point 0:02:05.360 --> 0:02:09.040 parrotfish poop. This is true of reef islands built entirely 0:02:09.080 --> 0:02:12.200 out of reef sediment, like the Maldives, but also true 0:02:12.240 --> 0:02:15.080 of some white sandy beaches in places like Hawaii and 0:02:15.120 --> 0:02:18.760 the Caribbean. We talked also about writings on parrotfish from 0:02:18.760 --> 0:02:23.120 the ancient world, how the Romans prized certain parrotfishes as 0:02:23.240 --> 0:02:26.160 food items, and why they thought they were in first 0:02:26.200 --> 0:02:30.200 place among the culinary uses of fish. How they developed 0:02:30.240 --> 0:02:32.840 a range of beliefs about these fish, some of which 0:02:32.880 --> 0:02:36.720 were fairly biologically accurate, such as the belief that these 0:02:36.760 --> 0:02:40.760 fish are herbivorous grazers they sort of are, and that 0:02:40.800 --> 0:02:44.160 they produce audible sounds underwater as they scrape the rocks 0:02:44.200 --> 0:02:47.400 and coral for food, also true. Other beliefs not quite 0:02:47.480 --> 0:02:50.200 so accurate. For example, Rob, didn't you talk about this 0:02:50.280 --> 0:02:53.680 idea that they like cooperate altruistically to save one another 0:02:53.720 --> 0:02:54.440 from traps? 0:02:55.040 --> 0:02:59.280 Yes, and in this became an enduring and long lasting 0:02:59.320 --> 0:03:02.799 symbol of free which doesn't really hold up to how 0:03:02.800 --> 0:03:03.760 they actually behave. 0:03:04.200 --> 0:03:07.040 But we also talked last time about some interesting beliefs 0:03:07.080 --> 0:03:11.119 about parrotfishes in Hawaiian mythology, where the parrotfish is sort 0:03:11.160 --> 0:03:14.440 of a progenitor of other sea life and enters into 0:03:14.520 --> 0:03:18.560 a pact with a Hawaiian mythical hero who can sort 0:03:18.560 --> 0:03:22.360 of call upon his friendship with the parrotfish in order 0:03:22.400 --> 0:03:25.600 to produce an abundance of fish catch for the people. 0:03:26.320 --> 0:03:29.440 And then finally, we also talked about research on parrotfish teeth, 0:03:29.480 --> 0:03:32.400 which are made out of some of the hardest, stiffest, 0:03:32.400 --> 0:03:36.040 and most resilient biominerals known even to the extent that 0:03:36.080 --> 0:03:39.360 they are being investigated as a model for high durability 0:03:39.640 --> 0:03:43.480 synthetic materials in the lab. So that was part one, 0:03:43.520 --> 0:03:46.160 and today we're back to talk some more about parrotfish. 0:03:46.480 --> 0:03:49.080 Yeah, and I just want to drive home that if 0:03:49.080 --> 0:03:52.600 you haven't had the opportunity to observe parrotfish in the wild, 0:03:53.440 --> 0:03:56.360 and you find yourself traveling to or in an area 0:03:56.760 --> 0:04:00.920 where there are reef environments and there is some manner 0:04:00.960 --> 0:04:04.680 of snorkeling going on, go check it out. Oftentimes, you 0:04:04.720 --> 0:04:08.520 know there are various snorkeling companies and and you know 0:04:08.560 --> 0:04:12.560 small businesses that are that are very approachable. You don't 0:04:12.600 --> 0:04:15.120 have to have a lot of experience to try these out. Again, 0:04:15.120 --> 0:04:19.160 these are often we're talking like shallow water environments, and 0:04:19.320 --> 0:04:23.440 in these environments there's almost always some sort of parrotfish 0:04:23.480 --> 0:04:27.400 to observe. And if that's not your cup of tea, 0:04:27.920 --> 0:04:30.200 I want to add that for anyone who would like 0:04:30.200 --> 0:04:32.880 to see various parrotfish in action as well as other fish, 0:04:33.240 --> 0:04:36.839 I highly recommend checking out Coral City Camera. It's that's 0:04:36.839 --> 0:04:39.600 just Coralcitycamera dot com, or you can look it up 0:04:39.600 --> 0:04:43.479 and search it's an underwater camera streaming live from an 0:04:43.600 --> 0:04:47.600 urban coral reef in Miami, Florida. Uh, it's it's pretty cool, 0:04:47.800 --> 0:04:51.360 and if you watch long enough, you will see some parrotfish. 0:04:50.800 --> 0:04:53.760 In action, pursuing their new career as streamers. 0:04:54.279 --> 0:04:57.920 Yes. Yes, so we're going to get into parrotfish reproduction 0:04:58.440 --> 0:05:01.000 here in a bit. But first up, we have this 0:05:01.640 --> 0:05:04.400 other delightful area to look at something that I wasn't 0:05:04.400 --> 0:05:07.280 familiar with at all concerning parrotfish. Joe, do you want 0:05:07.279 --> 0:05:08.640 to get into their mucus? 0:05:08.839 --> 0:05:11.360 Oh? Do? I? I feel like I'm already into their mucus. 0:05:11.440 --> 0:05:15.039 I've been in it all day. So I mentioned in 0:05:15.080 --> 0:05:18.920 the previous episode that the topic of parrotfish was one 0:05:18.960 --> 0:05:21.840 that I initially got interested in just by looking at pictures. 0:05:21.920 --> 0:05:22.080 You know. 0:05:22.200 --> 0:05:25.400 I was looking at like a photo of a parrotfish mouth, 0:05:25.680 --> 0:05:28.200 and I started thinking, what is going on with this 0:05:28.279 --> 0:05:32.040 awesome palisade of fused together teeth? And so there is 0:05:32.120 --> 0:05:35.279 another parrotfish subtopic that I think one could come to 0:05:35.360 --> 0:05:40.240 in exactly the same manner, and that is their mucus cocoons. 0:05:40.920 --> 0:05:45.279 If you look for photos of parrotfish sleeping, you will 0:05:45.320 --> 0:05:49.440 find images of these animals nestled down into cozy little 0:05:49.560 --> 0:05:52.839 niches in the seafloor or within the reef structure, sometimes 0:05:52.880 --> 0:05:56.040 kind of in a recess or a little heidi hole 0:05:56.080 --> 0:05:59.719 in the reef, surrounded by what looks like some kind 0:05:59.800 --> 0:06:04.200 of of film. Sometimes it looks like the parrotfish is 0:06:04.360 --> 0:06:09.360 enclosed within a gauzy, transparent orb covered like sometimes covered 0:06:09.360 --> 0:06:12.640 in glitter. If you see these in motion and rob 0:06:12.880 --> 0:06:15.240 below the photos here, I did attach a link to 0:06:15.279 --> 0:06:17.080 a video in the outline that you can look at 0:06:17.120 --> 0:06:19.839 so you can see it moving. If you see these 0:06:19.880 --> 0:06:22.479 in motion, they will they will appear to undulate in 0:06:22.560 --> 0:06:26.039 the water, so they're kind of jelly like in movement 0:06:26.120 --> 0:06:30.760 and substance. In other cases, this film looks like the 0:06:30.839 --> 0:06:34.679 fish is wrapped up inside a huge funnel spider web 0:06:34.760 --> 0:06:38.640 that's just covered in sand. Which funny thing about that 0:06:38.720 --> 0:06:41.880 the sand may of course be the parrotfish's own excretion 0:06:42.040 --> 0:06:42.640 from earlier. 0:06:43.120 --> 0:06:45.760 MM. Yeah, I'm looking at the video footage right now. 0:06:45.800 --> 0:06:49.560 It's it's slimy but beautiful. 0:06:50.200 --> 0:06:54.919 So what is this gossamer bubble around a slumbering fish. 0:06:55.640 --> 0:06:59.479 This is what's known as the parrotfish's mucous cocoon. Or 0:06:59.520 --> 0:07:04.840 sometimes in the scientific literature, it's mucus envelope, described by 0:07:04.839 --> 0:07:08.039 an author named H. E. Win in a scientific article 0:07:08.320 --> 0:07:13.080 in nineteen fifty five as a quote thin, transparent and 0:07:13.160 --> 0:07:17.960 gelatinous mucoid substance which starts as a fold at the 0:07:18.080 --> 0:07:22.680 mouth and progresses backwards in folds to surround the body. 0:07:24.160 --> 0:07:28.680 So parrotfish are daytime animals. They sleep during the night, 0:07:28.760 --> 0:07:32.240 they wake and feed during the day, and some species 0:07:32.280 --> 0:07:36.679 have been observed to spend roughly an hour before sleep 0:07:37.280 --> 0:07:41.680 generating this jelly like sleeping bag out of mucus from 0:07:41.760 --> 0:07:44.520 their mouths before actually getting to sleep, so it's like 0:07:44.560 --> 0:07:49.040 a bedtime routine. As night is falling, they start spitting 0:07:49.080 --> 0:07:52.200 out the mucus and it starts to envelop their body 0:07:52.240 --> 0:07:55.920 from front to back. So the fish are making themselves 0:07:56.040 --> 0:08:00.320 bedtime slime sacks. But why now? First, this is a 0:08:00.360 --> 0:08:03.400 side note. I just wanted to say it is normal 0:08:03.840 --> 0:08:07.600 for all kinds of fish species, not just parrotfish or 0:08:07.640 --> 0:08:12.360 the other related fish. Like some rasses that make these 0:08:12.400 --> 0:08:15.240 slime sacks. It is normal for all kinds of fish 0:08:15.360 --> 0:08:17.640 to be covered in a thin layer of mucus on 0:08:17.680 --> 0:08:22.000 the outside of their skin. This omnipresent slime barrier can 0:08:22.040 --> 0:08:25.200 provide a number of benefits, one of which is OSMO regulation, 0:08:25.600 --> 0:08:30.640 and that's maintaining the balance of internal water and solutes 0:08:30.840 --> 0:08:34.920 such as electrolytes, so for example, and OSMO regulation function 0:08:35.040 --> 0:08:38.439 within our bodies human bodies is maintaining the right level 0:08:38.480 --> 0:08:42.120 of salt in our body fluids. Mucous coverings on all 0:08:42.200 --> 0:08:46.960 kinds of fish help with OSMO regulation. But these mucous 0:08:47.160 --> 0:08:49.960 coverings on the skin also cut down on friction. So 0:08:50.000 --> 0:08:53.840 the slippery layer of mucus on the fish's skin makes 0:08:53.880 --> 0:08:57.200 it easier for the fish to swim along. It's like 0:08:57.240 --> 0:09:01.400 a lubricant for the interface with the surrounding water. It's 0:09:01.440 --> 0:09:04.880 also just physical protection of the skin from contact trauma 0:09:05.000 --> 0:09:08.559 such as cuts and scrapes. It in some cases provides 0:09:09.120 --> 0:09:13.200 UV radiation protection. In some cases might protect the fish 0:09:13.240 --> 0:09:17.040 from noxious chemicals or pollutants in the water, and provides 0:09:17.120 --> 0:09:19.120 the fish protection against drying out. 0:09:20.200 --> 0:09:22.440 So this is of course one of the potential issues. 0:09:22.480 --> 0:09:24.679 And just handling fish such as then like ketch and 0:09:24.760 --> 0:09:27.760 release and so forth. The slime isn't just something that's 0:09:27.760 --> 0:09:29.760 on the fish. It's an active barrier. 0:09:30.360 --> 0:09:33.800 Yeah, but that's all just the normal mucous coating common 0:09:33.840 --> 0:09:36.400 to many many fish. What we're talking about here is 0:09:36.400 --> 0:09:41.760 specifically this baggy mucous hyper sleep pod that forms around 0:09:41.760 --> 0:09:45.160 some parrotfish and rasses through the night. So I started 0:09:45.160 --> 0:09:47.720 looking at scientific papers about this to see what I 0:09:47.720 --> 0:09:50.960 could find out. So first I was looking at a 0:09:51.080 --> 0:09:54.920 marine zoology paper from the year nineteen seventy that investigated 0:09:54.920 --> 0:09:58.200 a few species of parrotfish to see how and under 0:09:58.240 --> 0:10:02.160 what conditions the fish would make these cocoons. So this 0:10:02.200 --> 0:10:05.360 is by John E. Byrne, who was a professor of 0:10:05.440 --> 0:10:08.800 zoology at the University of Hawaii. The paper is called 0:10:08.880 --> 0:10:13.840 Mucus envelope formation in two species of Hawaiian parrotfishes, and 0:10:13.880 --> 0:10:17.200 the paper begins by citing previous research by Win and 0:10:17.280 --> 0:10:21.040 co authors on parrotfish from the coral reefs of Bermuda, 0:10:21.600 --> 0:10:25.480 which were observed to make mucus envelopes at night. So 0:10:25.720 --> 0:10:28.960 when and a co author named Bardak argued that the 0:10:29.000 --> 0:10:33.480 purpose of the mucus cocoon of the slimesack was to 0:10:33.600 --> 0:10:38.959 protect the parrotfish from predators while it was sleeping. And 0:10:39.000 --> 0:10:42.439 this is a hypothesis that I've seen repeated in a 0:10:42.520 --> 0:10:47.280 number of sources that maybe somehow the mucus covering will 0:10:47.280 --> 0:10:50.640 help alert the fish more quickly if a predator gets 0:10:50.679 --> 0:10:53.520 close to it, or may in some way help mask 0:10:53.720 --> 0:10:57.520 the fish, maybe mask the fish is sent from predators, 0:10:57.960 --> 0:11:00.640 or provide some kind of benefit along these lines. 0:11:01.080 --> 0:11:04.400 Okay, So either to some degree a cloaking system, a 0:11:04.440 --> 0:11:07.160 cloaking device, if you will, or perhaps some sort of 0:11:07.200 --> 0:11:10.040 like added security trip wire made out of mucus. 0:11:10.640 --> 0:11:12.800 There you go. Now we'll get to another explanation in 0:11:12.920 --> 0:11:14.560 just a bit here, but we're not there quite yet. 0:11:14.600 --> 0:11:16.960 First we're gonna look at like how and how and 0:11:17.080 --> 0:11:19.760 when these things form. So the author of the study, 0:11:19.880 --> 0:11:24.520 John Burn, begins by investigating envelope formation in a couple 0:11:24.559 --> 0:11:28.720 of different species of parrotfish. There's scare Us dubious, commonly 0:11:28.760 --> 0:11:34.160 known as the regal parrotfish, and scaus parsp pair. Oh wow, 0:11:34.640 --> 0:11:38.520 here's a word, pers bisilatis. There you go, which is 0:11:38.559 --> 0:11:42.160 commonly called the spectacled parrotfish. Both are found in the 0:11:42.160 --> 0:11:45.920 reefs around Hawaii, and I think the spectacled parrotfish may 0:11:45.920 --> 0:11:49.200 be one of the keyfish referred to as oohu and 0:11:49.280 --> 0:11:51.920 some of the Hawaiian legends that we talked about in 0:11:51.960 --> 0:11:52.880 the last episode. 0:11:53.160 --> 0:11:55.359 Yeah. Yeah, So burn. 0:11:55.360 --> 0:11:58.439 Did some experiments on these two species in his laboratory, 0:11:58.840 --> 0:12:03.320 varying conditions of light and darkness within their aquaria, making 0:12:03.440 --> 0:12:07.720 observations of behavior, and then examining the mucus producing organs. 0:12:08.080 --> 0:12:13.280 So Previous field observations had found that as daylight intensities decrease. 0:12:13.320 --> 0:12:17.679 As daylight goes down, fewer parrotfishes can be found swimming 0:12:17.679 --> 0:12:21.160 around the reefs for the night time, these fish will 0:12:21.480 --> 0:12:25.000 disperse their schools and go into recesses within the reef 0:12:25.040 --> 0:12:28.640 to hide and sleep, and that's where they generate these cocoons. 0:12:29.760 --> 0:12:33.080 Within the lab environment, Burne found that if you shine 0:12:33.120 --> 0:12:36.640 a constant light on these fish for twenty four hours straight, 0:12:37.080 --> 0:12:39.719 they will actually never make a mucus cocoon. You just 0:12:39.840 --> 0:12:41.920 keep shining the light on them, at least for twenty 0:12:41.920 --> 0:12:44.920 four hours. He didn't push the experiment to go that 0:12:45.040 --> 0:12:48.120 much longer, because you know, it might just end up 0:12:48.120 --> 0:12:50.960 harming them overall. But for twenty four hours straight, you 0:12:51.000 --> 0:12:53.880 shine a light on them and it, you know, nothing happens. 0:12:54.200 --> 0:12:55.600 Yeah, corp, of course, I mean, there are a lot 0:12:55.640 --> 0:12:58.439 of things I'm not going to do of some sort 0:12:58.440 --> 0:13:03.360 of an intelligent being from highly advanced species shines artificial 0:13:03.400 --> 0:13:04.880 light on me for twenty four hours. 0:13:05.040 --> 0:13:07.360 That's right, So the constant light means you never make 0:13:07.400 --> 0:13:10.559 a pod. However, when darkness was introduced, you turned the 0:13:10.640 --> 0:13:14.520 lights off. This triggered twenty two of the thirty parrot 0:13:14.559 --> 0:13:18.200 fish tested to build mucous envelopes, and it was the 0:13:18.240 --> 0:13:22.360 same frequency in the two different species. The fish took 0:13:22.520 --> 0:13:25.880 different amounts of time to finish building their envelopes after 0:13:25.920 --> 0:13:29.000 the light was turned off. The minimum was like thirty minutes, 0:13:29.080 --> 0:13:32.360 maximum was two hundred and forty minutes. Average building time 0:13:32.559 --> 0:13:36.880 was about seventy minutes. However, if you kept the fish 0:13:37.000 --> 0:13:39.640 the parrot fish in the dark after it made its cocoon, 0:13:40.360 --> 0:13:42.760 it did not stay in the cocoon forever. Eventually it 0:13:42.760 --> 0:13:46.760 would emerge on its own. So what did they do 0:13:46.840 --> 0:13:50.120 when they made these things? They would typically rest their 0:13:50.160 --> 0:13:54.040 bodies on the floor of the tank and the seafloor 0:13:54.080 --> 0:13:57.000 in the wild in an upright position, almost always with 0:13:57.120 --> 0:14:00.559 one side of the body resting against a vertical surface 0:14:00.679 --> 0:14:02.960 like a rock or a coral wall, or, in the 0:14:02.960 --> 0:14:06.280 case of the lab experiments, the aquarium wall, and then 0:14:06.320 --> 0:14:10.240 the cocoon begins. It begins formation at the front of 0:14:10.280 --> 0:14:15.080 the fish around its mouth, and folds of mucus slowly 0:14:15.200 --> 0:14:19.160 move back along the length of the body toward the tail. 0:14:19.200 --> 0:14:23.880 Though interestingly, the mucus never completely closes over the body. 0:14:24.240 --> 0:14:26.800 There is always at least a one to two centimeter 0:14:27.000 --> 0:14:29.840 gap at the back end of the bubble, and Burn 0:14:29.960 --> 0:14:34.760 believes this hole is to evacuate respiratory water that's forced 0:14:34.760 --> 0:14:39.360 out of the buckle cavity, so sort of a breathing hole. Now, 0:14:39.480 --> 0:14:41.440 I mentioned that in a lot of these photos, the 0:14:41.480 --> 0:14:44.840 mucus coccoon seems to sparkle as if it is covered 0:14:44.840 --> 0:14:49.080 in glitter. Burn writes that quote fine debris adhered to 0:14:49.120 --> 0:14:54.160 the envelope's exterior and the outline was thus more clearly defined. However, 0:14:54.200 --> 0:14:57.000 he says this coating of sediment and debris makes the 0:14:57.040 --> 0:15:00.840 bubble appear thin and delicate. This is how Wind described 0:15:00.880 --> 0:15:05.280 it in that article from the fifties. But Burn did 0:15:05.320 --> 0:15:10.480 an experiment by injecting pigmented particles into the cocoon and 0:15:10.600 --> 0:15:13.720 revealed that actually appearances can be deceiving here because the 0:15:13.760 --> 0:15:16.800 cocoon often does look very thin. It's like a you know, 0:15:16.880 --> 0:15:21.880 wispy spider web or this very very thin kind of 0:15:21.880 --> 0:15:24.760 gossamer like material. But in fact he found when he 0:15:24.960 --> 0:15:28.720 injected the pigmented particles in there, the mucus structure was 0:15:28.920 --> 0:15:32.040 up to six centimeters thick in some places. So it's 0:15:32.080 --> 0:15:33.960 not as wispy as it looks. 0:15:33.960 --> 0:15:35.880 Okay, This would just be the case of there being 0:15:35.920 --> 0:15:40.720 like a thin layer of particles on top of this 0:15:41.200 --> 0:15:45.720 otherwise translucent or semi translucent mucus shielding. They would give 0:15:45.720 --> 0:15:48.080 it the appearance of being super thin when in fact 0:15:48.120 --> 0:15:49.640 it is probably thicker. 0:15:49.920 --> 0:15:53.680 That's right. So dissection of the fish revealed that the 0:15:54.440 --> 0:15:59.280 presence of gland tissue in the buckle cavity correlated with 0:15:59.400 --> 0:16:01.960 whether or not the fish would make a cocoon. It 0:16:02.040 --> 0:16:05.320 was found that fish that did not have this gland 0:16:05.440 --> 0:16:08.800 tissue in the mouth cavity, they did not form the 0:16:08.920 --> 0:16:13.680 mucus cocoons. So that's how they're made and win. But 0:16:13.720 --> 0:16:17.000 what are they for? Well, again, the burn paper mentions 0:16:17.040 --> 0:16:20.920 this hypothesis that the mucus sleeping bag somehow protects the 0:16:21.000 --> 0:16:25.520 fish from large predators. A commonly mentioned predator in the 0:16:25.560 --> 0:16:28.000 reef environment would be the more eel. You know, and 0:16:28.000 --> 0:16:30.400 it can get down there in the recesses and attack. 0:16:31.000 --> 0:16:34.720 But apparently there's some doubt about this because, for example, 0:16:34.720 --> 0:16:37.920 when faced with reef dwelling predators such as more eels, 0:16:38.320 --> 0:16:42.040 there is some evidence that sleeping fish within within a 0:16:42.120 --> 0:16:46.680 cocoon are still vulnerable, like they still get eaten. But 0:16:46.800 --> 0:16:49.840 actually I came across an interesting twenty eleven paper that 0:16:49.960 --> 0:16:53.480 looked directly into the function of the mucus cocoon and 0:16:53.800 --> 0:16:57.040 came to a different conclusion. So this was published in 0:16:57.080 --> 0:17:00.920 the journal Biology Letters by Grutterer at All and the 0:17:01.040 --> 0:17:03.360 title is this will give some of the findings away 0:17:03.720 --> 0:17:09.080 fish mucus cocoons the mosquito nets of the sea. This 0:17:09.160 --> 0:17:12.399 was in the year twenty eleven. So in this paper 0:17:12.440 --> 0:17:16.280 the authors look at another hypothesis, which is the idea 0:17:16.359 --> 0:17:21.600 that mucus envelopes actually protect the fish inside from parasites 0:17:21.880 --> 0:17:27.840 such as ectoparasitic nathid isopods. These are these little bloodsucking 0:17:27.920 --> 0:17:32.160 parasites that live throughout the ocean, often compared to terrestrial 0:17:32.240 --> 0:17:36.719 mosquitoes and ticks. Raw I attached to a little photo 0:17:36.760 --> 0:17:38.479 of these things for you to look at. They're kind 0:17:38.480 --> 0:17:41.320 of shrimp like in appearance maybe look like a cross 0:17:41.359 --> 0:17:44.600 between a shrimp and a tick. Yeah yeah, And the 0:17:44.600 --> 0:17:48.159 authors point out that during the daytime, when parrotfish are 0:17:48.240 --> 0:17:51.760 swimming around, they actually get some help. They get some 0:17:51.840 --> 0:17:56.239 protection against blood drinking isopods from cleaner fish. You know, 0:17:56.320 --> 0:17:59.359 this is a relationship where a smaller fish that wants 0:17:59.400 --> 0:18:03.440 to eat these parasites will come along and help pick 0:18:03.480 --> 0:18:06.040 them off to sort of groom the outside of the 0:18:06.480 --> 0:18:11.080 larger fish. But how do the fish protect themselves at night. 0:18:11.600 --> 0:18:14.640 The idea behind this experiment was that maybe the mucus 0:18:14.640 --> 0:18:18.640 cocoon functions like a mosquito net to protect the sleeping 0:18:18.720 --> 0:18:24.399 fish from these heimatophagous parasites. So they tested this hypothesis 0:18:24.440 --> 0:18:29.199 on the coral reef parrotfish Chlorurus sordid us. And the 0:18:29.200 --> 0:18:31.160 way they tested it was they got some of these fish, 0:18:31.200 --> 0:18:34.440 they separated them into groups that would sleep with and 0:18:34.600 --> 0:18:38.240 without the benefit of cocoons in the presence of these 0:18:38.240 --> 0:18:41.560 isopod parasites. And actually, the way they did it was 0:18:41.600 --> 0:18:45.240 they took a subset of cocoon fish and found a 0:18:45.240 --> 0:18:47.480 way to sort of gently push them out of their 0:18:47.560 --> 0:18:53.119 envelopes without waking them up. So what do they find Yes, indeed, 0:18:53.200 --> 0:18:57.480 the fish without the mucus bag experienced way more attacks 0:18:57.520 --> 0:19:01.359 by parasites. How much more well, about ninety five percent 0:19:01.400 --> 0:19:05.320 of the fish without cocoons were attacked by isopods and 0:19:05.359 --> 0:19:08.640 only about ten percent of the fish with cocoons were attacked. 0:19:08.800 --> 0:19:12.000 So huge difference, all right, Right, so yeah, coming back 0:19:12.000 --> 0:19:15.400 to the mosquito net comparisons, Like, initially we looked at 0:19:15.400 --> 0:19:17.600 it and we're like, this mosquito net must protect the 0:19:17.640 --> 0:19:21.680 sleeper from bears, but in reality it protects them from 0:19:21.920 --> 0:19:25.000 mosquitoes and similar insects that sort of thing. 0:19:25.359 --> 0:19:30.360 Or maybe even something downstream from mosquitoes in the analogy here, 0:19:30.400 --> 0:19:34.960 because the authors also investigated the question of how energetically 0:19:35.080 --> 0:19:39.199 costly it is for the fish to make these mucous orbs, 0:19:39.680 --> 0:19:42.320 and they calculated that it takes about two point five 0:19:42.400 --> 0:19:46.399 percent of a fish's daily energy budget to make the 0:19:46.520 --> 0:19:50.040 mucus bag. Now, when I first saw that figure, I 0:19:50.119 --> 0:19:52.280 kind of thought, oh, hey, that seems fairly cheap, only 0:19:52.280 --> 0:19:55.800 two point five percent. But actually I was reading some 0:19:56.359 --> 0:19:59.919 news reporting on this that quoted the lead author, Alexandra Grutterer, 0:20:00.600 --> 0:20:03.560 and she framed it a different way. She said, quote 0:20:03.680 --> 0:20:06.320 the amount of effort that goes into building these cocoons, 0:20:06.359 --> 0:20:09.879 which requires fish to have developed very large glands about 0:20:09.880 --> 0:20:13.879 the size of a quarter to produce the cocoons, is extraordinary. 0:20:14.480 --> 0:20:18.239 Parasites must exert an enormous pressure on these fish in 0:20:18.359 --> 0:20:20.840 order for the fish to have evolved such a specific 0:20:20.880 --> 0:20:24.760 way of avoiding the parasites. So what could be so pressing? 0:20:24.840 --> 0:20:26.600 Is it really just that you don't want to get 0:20:26.600 --> 0:20:29.119 bitten by these isopods and have them drink some of 0:20:29.160 --> 0:20:33.800 your blood? Well, Grutterer mentions the possibility that the blood 0:20:34.000 --> 0:20:37.600 directly lost to the parasite might not be the only cost. 0:20:38.080 --> 0:20:43.480 These isopods may also transmit a secondary endo parasite which 0:20:43.600 --> 0:20:48.280 lives in the fish's blood, much like how mosquitoes transmit 0:20:48.400 --> 0:20:52.920 malaria in humans. So the mosquitoes themselves are annoying and 0:20:53.040 --> 0:20:56.240 you don't like the mosquitoes, but the malaria is much 0:20:56.280 --> 0:21:00.119 more concerning than the mosquito. Malaria can be deadly in 0:21:00.160 --> 0:21:03.080 a similar way. It's possible that it's worth it for 0:21:03.160 --> 0:21:07.680 these fish to build these slimy bionets to protect themselves 0:21:07.960 --> 0:21:11.879 from blood disease. Wow, so it seems like a good trade. 0:21:11.960 --> 0:21:15.040 You spend a little energy to weave a slime tube 0:21:15.560 --> 0:21:19.080 before bed. Every night, you sleep without these tiny shrimp 0:21:19.119 --> 0:21:22.720 monsters drinking your blood, possibly giving you diseases of the blood. 0:21:23.200 --> 0:21:25.199 And it all works out. And in fact, there was 0:21:25.200 --> 0:21:29.280 one more observation from grutter speaking to the media that 0:21:30.359 --> 0:21:33.480 kind of maybe there's a strategy to recoop some of 0:21:33.480 --> 0:21:37.160 that nightly cost. So Grutterer says, quote, I have observed 0:21:37.160 --> 0:21:40.359 on occasion a fish at dawn with what appeared to 0:21:40.400 --> 0:21:44.560 be mucus stuffed in its mouth. And then she goes 0:21:44.600 --> 0:21:47.000 on to say she has seen other fish, not parrotfish, 0:21:47.000 --> 0:21:51.959 but related fish that also produce mucus cocoons pecking it 0:21:52.240 --> 0:21:55.600 at its old cocoons in the morning. So like recooping 0:21:55.600 --> 0:21:59.000 some of that nightly cost by eating the mucus that 0:21:59.040 --> 0:21:59.960 you created before. 0:22:00.760 --> 0:22:03.320 I mean, that's just it's economically sound. It's like if 0:22:03.440 --> 0:22:08.040 humans produce, say an ectoplasm defense shield at night, you 0:22:08.080 --> 0:22:10.680 would want to to recoup that cost, and that might 0:22:10.760 --> 0:22:13.199 mean consuming all that actoplasm again and getting all that 0:22:14.000 --> 0:22:17.840 liquid back into your body. You know, it reminds us 0:22:17.840 --> 0:22:21.880 of other examples we've looked at in biology, such as 0:22:22.080 --> 0:22:26.200 various reptiles that will eat their own shed skin because 0:22:26.359 --> 0:22:27.840 you know, why waste that, you know. 0:22:28.040 --> 0:22:31.640 Yeah, so may still provide some kind of benefit against 0:22:31.960 --> 0:22:36.600 larger macroscopic predators too. Not certain about that, but it 0:22:36.640 --> 0:22:38.840 does seem like there's a very good case that these 0:22:38.920 --> 0:22:42.200 mucous bags help prevent against parasite attacks. 0:22:42.359 --> 0:22:55.440 Very fascinating, all right, And so for the rest of 0:22:55.480 --> 0:22:57.720 the episode, we're going to turn to the world of 0:22:57.760 --> 0:23:02.000 parrot fish reproduction and pair fish sex. So, as we 0:23:02.040 --> 0:23:04.000 teach out in the first episode, one of the other 0:23:04.600 --> 0:23:09.720 amazing aspects of parrotfish biology broadly is that they change 0:23:09.760 --> 0:23:13.480 sex during the course of a normal lifetime. That's to say, 0:23:13.880 --> 0:23:16.680 this is not something that occurs, you know, only when 0:23:16.680 --> 0:23:20.479 certain environmental conditions are right. It occurs as part of 0:23:20.520 --> 0:23:22.440 a normal life cycle. 0:23:22.520 --> 0:23:25.000 And within a fairly predictable pattern, right. 0:23:25.200 --> 0:23:27.520 That's right. Yeah, And they're going to be a couple 0:23:27.560 --> 0:23:29.879 of exceptions. Again, as we've been distressing, there are a 0:23:30.040 --> 0:23:35.840 number of different species of parrotfish, but still the vast 0:23:35.840 --> 0:23:40.960 majority of them do follow this example that we're going 0:23:41.000 --> 0:23:46.640 to be discussing. So they are proto gynos that means 0:23:46.680 --> 0:23:52.040 female first, hermaphrodites that always turn into males if they 0:23:52.080 --> 0:23:54.920 live long enough, so they're born female and then at 0:23:54.920 --> 0:23:58.199 a certain point during their development they become male and 0:23:58.280 --> 0:24:00.560 live out the rest of their life as a male. 0:24:00.840 --> 0:24:03.439 And this would feedback into something we talked about in 0:24:03.440 --> 0:24:08.280 the first episode, which is sometimes difficulty in identifying parrotfish 0:24:08.320 --> 0:24:11.880 species because they undergo these changes, and these changes come 0:24:11.960 --> 0:24:14.280 with changes to their outer appearance. 0:24:14.520 --> 0:24:17.719 That's right along the way, multiple changes in colorization take place, 0:24:18.119 --> 0:24:20.520 some of which have to do with just aging, some 0:24:20.600 --> 0:24:23.680 of which have to do with changing their sex, and 0:24:23.840 --> 0:24:29.480