WEBVTT - The Parrotfish, Part 2 0:00:03.080 --> 0:00:07.160 Welcome to Stuff to Blow Your Mind production of iHeartRadio. 0:00:12.880 --> 0:00:15.120 Hey, welcome to Stuff to Blow Your Mind. My name 0:00:15.160 --> 0:00:16.200 is Robert Lamb. 0:00:16.200 --> 0:00:18.560 And I am Joe McCormick, and we're back with Part 0:00:18.600 --> 0:00:22.720 two in our series on parrotfish, a group of related 0:00:22.800 --> 0:00:27.440 fishes containing about ninety to one hundred species worldwide, notable 0:00:27.560 --> 0:00:31.400 for their powerful beak like mouths made out of rows 0:00:31.400 --> 0:00:36.160 of fused teeth. In the previous episode, we talked about 0:00:36.200 --> 0:00:40.280 some basics about the biology and taxonomy of parrotfish species. 0:00:40.760 --> 0:00:44.600 We talked about their diet and feeding behavior. Parrotfish are 0:00:44.680 --> 0:00:49.519 usually considered herbivores or something equivalent to herbivores. They survived 0:00:49.600 --> 0:00:54.120 by grazing for algae, microorganisms, to trite us, and sometimes 0:00:54.200 --> 0:00:58.520 invertebrate animals like coral polyps, along the surfaces of rocks 0:00:58.560 --> 0:01:03.520 and coral skeletons within coral reef environments. We talked about 0:01:03.560 --> 0:01:07.399 the fact that some parrotfish species end up biting or 0:01:07.600 --> 0:01:11.959 scraping off significant chunks of hard matter from the rocks 0:01:12.000 --> 0:01:15.240 and coral that they scour for food, and then grinding 0:01:15.319 --> 0:01:20.040 up these coral skeletons and minerals in their phyryngial mills. 0:01:20.240 --> 0:01:23.280 It's kind of like horror movie machinery in the back 0:01:23.319 --> 0:01:25.120 of their throats. I think we compared it to like 0:01:25.160 --> 0:01:29.760 a bone transmission gear and then defecating what's left in 0:01:29.800 --> 0:01:32.840 the form of sand. And so as a result, parrotfish 0:01:32.840 --> 0:01:36.000 are major figures in the erosion of coral reefs and 0:01:36.080 --> 0:01:38.840 in the production of sand. So if you walk across 0:01:38.880 --> 0:01:41.720 a white sandy beach in the tropics where there are 0:01:41.800 --> 0:01:44.880 coral reefs nearby, there is a good chance that most 0:01:44.959 --> 0:01:47.840 of the sand under your feet was at one point 0:01:47.920 --> 0:01:51.600 parrotfish poop. This is true of reef islands built entirely 0:01:51.640 --> 0:01:54.760 out of reef sediment, like the Maldives, but also true 0:01:54.800 --> 0:01:57.640 of some white sandy beaches in places like Hawaii and 0:01:57.680 --> 0:02:01.320 the Caribbean. We talked also about writings on parrotfish from 0:02:01.320 --> 0:02:05.680 the ancient world, how the Romans prized certain parrotfishes as 0:02:05.800 --> 0:02:08.720 food items, and why they thought they were in first 0:02:08.760 --> 0:02:12.760 place among the culinary uses of fish. How they developed 0:02:12.800 --> 0:02:15.400 a range of beliefs about these fish, some of which 0:02:15.440 --> 0:02:19.280 were fairly biologically accurate, such as the belief that these 0:02:19.320 --> 0:02:23.320 fish are herbivorous grazers they sort of are, and that 0:02:23.360 --> 0:02:26.720 they produce audible sounds underwater as they scrape the rocks 0:02:26.760 --> 0:02:29.960 and coral for food. Also true, other beliefs not quite 0:02:30.040 --> 0:02:32.760 so accurate. For example, Rob, didn't you talk about this 0:02:32.840 --> 0:02:37.480 idea that they cooperate altruistically to save one another from traps? 0:02:37.600 --> 0:02:41.840 Yes, and in this became an enduring and long lasting 0:02:41.880 --> 0:02:45.359 symbol of friendship, which doesn't really hold up to how 0:02:45.360 --> 0:02:46.320 they actually behave. 0:02:46.760 --> 0:02:49.600 But we also talked last time about some interesting beliefs 0:02:49.639 --> 0:02:53.679 about parrotfishes in Hawaiian mythology, where the parrotfish is sort 0:02:53.720 --> 0:02:57.000 of a progenitor of other sea life and enters into 0:02:57.080 --> 0:03:01.119 a pact with a Hawaiian mythical hero who can sort 0:03:01.120 --> 0:03:04.920 of call upon his friendship with the parrotfish in order 0:03:04.960 --> 0:03:08.160 to produce an abundance of fish catch for the people. 0:03:08.880 --> 0:03:12.000 And then finally, we also talked about research on parrotfish teeth, 0:03:12.040 --> 0:03:14.960 which are made out of some of the hardest, stiffest, 0:03:14.960 --> 0:03:18.600 and most resilient biominerals known, even to the extent that 0:03:18.639 --> 0:03:21.920 they are being investigated as a model for high durability 0:03:22.200 --> 0:03:26.040 synthetic materials in the lab. So that was part one, 0:03:26.080 --> 0:03:28.840 and today we're back to talk some more about parrotfish. 0:03:29.040 --> 0:03:31.639 Yeah, And I just want to drive home that if 0:03:31.639 --> 0:03:35.160 you haven't had the opportunity to observe parrotfish in the wild, 0:03:35.720 --> 0:03:38.920 and you find yourself traveling to or in an area 0:03:39.320 --> 0:03:43.480 where there are reef environments and there is some manner 0:03:43.520 --> 0:03:47.360 of snorkeling going on, go check it out. Oftentimes, you know, 0:03:47.360 --> 0:03:53.520 there are various snorkeling companies and small businesses that are 0:03:53.600 --> 0:03:55.720 very approachable. You don't have to have a lot of 0:03:55.720 --> 0:03:58.800 experience to try these out. Again. These are often we're 0:03:58.840 --> 0:04:03.200 talking like shallow water environments, and in these environments there's 0:04:03.240 --> 0:04:08.200 almost always some sort of parrotfish to observe. And if 0:04:08.280 --> 0:04:11.680 that's not your cup of tea, I want to add 0:04:11.680 --> 0:04:13.880 that for anyone who would like to see various parrotfish 0:04:13.880 --> 0:04:16.640 in action as well as other fish, I highly recommend 0:04:16.680 --> 0:04:21.200 checking out Coral City Camera. That's just Coralcitycamera dot com 0:04:21.320 --> 0:04:23.560 or you can look it up and search. It's an 0:04:23.600 --> 0:04:28.599 underwater camera streaming live from an urban coral reef in Miami, Florida. 0:04:29.120 --> 0:04:31.960 It's pretty cool and if you watch long enough, you 0:04:32.000 --> 0:04:33.920 will see some parrotfish. 0:04:33.360 --> 0:04:36.320 In action pursuing their new career as streamers. 0:04:36.839 --> 0:04:40.480 Yes, yes, so We're going to get into parrotfish reproduction 0:04:41.000 --> 0:04:43.560 here in a bit, But first up, we have this 0:04:44.200 --> 0:04:46.960 other delightful area to look at something that I wasn't 0:04:46.960 --> 0:04:49.840 familiar with at all concerning parrotfish. Joe, do you want 0:04:49.839 --> 0:04:51.200 to get into their mucus? 0:04:51.400 --> 0:04:51.599 Oh? 0:04:51.680 --> 0:04:52.080 Do? I? 0:04:52.080 --> 0:04:54.280 I feel like I'm already into their mucus. I've been 0:04:54.320 --> 0:04:58.200 in it all day. So I mentioned in the previous 0:04:58.240 --> 0:05:02.240 episode that the topic parrotfish was one that I initially 0:05:02.240 --> 0:05:04.640 got interested in just by looking at pictures, you know. 0:05:04.760 --> 0:05:07.960 I was looking at like a photo of a parrotfish mouth, 0:05:08.240 --> 0:05:10.760 and I started thinking, what is going on with this 0:05:10.839 --> 0:05:14.640 awesome palisade of fused together teeth? And so there is 0:05:14.680 --> 0:05:17.839 another parrotfish subtopic that I think one could come to 0:05:17.920 --> 0:05:22.800 in exactly the same manner, and that is their mucous cocoons. 0:05:23.480 --> 0:05:27.839 If you look for photos of parrotfish sleeping, you will 0:05:27.880 --> 0:05:32.000 find images of these animals nestled down into cozy little 0:05:32.120 --> 0:05:35.400 niches in the seafloor or within the reef structure, sometimes 0:05:35.440 --> 0:05:38.600 kind of in a recess or a little heidi hole 0:05:38.640 --> 0:05:42.400 in the reef, surrounded by what looks like some kind 0:05:42.560 --> 0:05:47.560 of film. Sometimes it looks like the parrotfish is enclosed 0:05:47.640 --> 0:05:52.479 within a gauzy, transparent orb covered like sometimes covered in glitter. 0:05:53.400 --> 0:05:55.839 If you see these in motion and rob below the 0:05:55.880 --> 0:05:58.240 photos here, I did attach a link to a video 0:05:58.320 --> 0:05:59.760 in the outline that you can look at so you 0:05:59.800 --> 0:06:02.919 can see it moving. If you see these in motion, 0:06:03.040 --> 0:06:06.080 they will appear to undulate in the water, so they're 0:06:06.160 --> 0:06:10.840 kind of jelly like in movement and substance. In other cases, 0:06:11.400 --> 0:06:15.200 this film looks like the fish is wrapped up inside 0:06:15.240 --> 0:06:18.880 a huge funnel spider web that's just covered in sand. 0:06:19.600 --> 0:06:22.400 Which funny thing about that the sand may of course 0:06:22.480 --> 0:06:25.240 be the parrotfish's own excretion from earlier. 0:06:26.600 --> 0:06:30.479 Yeah, I'm looking at the video footage right now. It's 0:06:30.520 --> 0:06:32.120 slimy but beautiful. 0:06:32.800 --> 0:06:37.480 So what is this gossamer bubble around a slumbering fish? 0:06:38.200 --> 0:06:42.039 This is what's known as the parrotfish's mucous cocoon, or 0:06:42.080 --> 0:06:47.400 sometimes in the scientific literature it's mucous envelope, described by 0:06:47.440 --> 0:06:50.599 an author named H. E. Wynn in a scientific article 0:06:50.880 --> 0:06:55.640 in nineteen fifty five as a quote thin, transparent and 0:06:55.720 --> 0:07:00.960 gelatinous mucoid substance which starts as a full the mouth 0:07:01.320 --> 0:07:06.840 and progresses backwards in folds to surround the body. So 0:07:07.200 --> 0:07:11.480 parrotfish are daytime animals. They sleep during the night, they 0:07:11.520 --> 0:07:15.080 wake and feed during the day, and some species have 0:07:15.120 --> 0:07:20.600 been observed to spend roughly an hour before sleep generating 0:07:20.960 --> 0:07:24.520 this jelly like sleeping bag out of mucus from their 0:07:24.560 --> 0:07:27.240 mouths before actually getting to sleep, so it's like a 0:07:27.240 --> 0:07:31.840 bedtime routine. As night is falling, they start spitting out 0:07:31.840 --> 0:07:35.000 the mucus and it starts to envelop their body from 0:07:35.000 --> 0:07:39.240 front to back. So the fish are making themselves bedtime 0:07:39.360 --> 0:07:43.720 slime sacks. But why now? First, as a side note, 0:07:44.120 --> 0:07:46.760 I just wanted to say it is normal for all 0:07:46.840 --> 0:07:50.520 kinds of fish species, not just parrotfish or the other 0:07:50.600 --> 0:07:55.760 related fish. Like some rasses that make these slime sacks. 0:07:55.920 --> 0:07:58.160 It is normal for all kinds of fish to be 0:07:58.200 --> 0:08:00.800 covered in a thin layer of mucus on the outside 0:08:00.800 --> 0:08:05.000 of their skin. This omnipresent slime barrier can provide a 0:08:05.080 --> 0:08:08.280 number of benefits, one of which is osmo regulation, and 0:08:08.320 --> 0:08:13.600 that's maintaining the balance of internal water and solutes such 0:08:13.600 --> 0:08:17.800 as electrolytes. So for example, and osmo regulation function within 0:08:17.880 --> 0:08:21.120 our bodies. Human bodies is maintaining the right level of 0:08:21.280 --> 0:08:25.000 salt in our body fluids. Mucous coverings on all kinds 0:08:25.040 --> 0:08:30.240 of fish help with OSMO regulation. But these mucous coverings 0:08:30.240 --> 0:08:32.880 on the skin also cut down on friction. So the 0:08:33.000 --> 0:08:36.560 slippery layer of mucus on the fish's skin makes it 0:08:36.600 --> 0:08:39.839 easier for the fish to swim along. It's like a 0:08:39.920 --> 0:08:44.240 lubricant for the interface with the surrounding water. It's also 0:08:44.400 --> 0:08:47.760 just physical protection of the skin from contact trauma such 0:08:47.760 --> 0:08:51.880 as cuts and scrapes. It in some cases provides UV 0:08:52.040 --> 0:08:56.040 radiation protection, in some cases might protect the fish from 0:08:56.120 --> 0:08:59.720 noxious chemicals or pollutants in the water, and provides the 0:08:59.720 --> 0:09:01.680 fish protection against drying out. 0:09:02.760 --> 0:09:05.000 So this is of course one of the potential issues. 0:09:05.040 --> 0:09:07.280 And just handling fish such as then like catch and 0:09:07.320 --> 0:09:10.320 release and so forth. The slime isn't just something that's 0:09:10.320 --> 0:09:12.320 on the fish. It's an active barrier. 0:09:12.920 --> 0:09:16.360 Yeah, But that's all just the normal mucus coating common 0:09:16.400 --> 0:09:18.959 to many many fish. What we're talking about here is 0:09:18.960 --> 0:09:24.320 specifically this baggy mucus hyper sleep pod that forms around 0:09:24.360 --> 0:09:27.720 some parrotfish and rasses through the night. So I started 0:09:27.760 --> 0:09:30.280 looking at scientific papers about this to see what I 0:09:30.280 --> 0:09:33.520 could find out. So first I was looking at a 0:09:33.640 --> 0:09:37.480 marine zoology paper from the year nineteen seventy that investigated 0:09:37.520 --> 0:09:40.760 a few species of parrotfish to see how and under 0:09:40.800 --> 0:09:44.719 what conditions the fish would make these cocoons. So this 0:09:44.800 --> 0:09:47.920 is by John E. Byrne, who was a professor of 0:09:48.000 --> 0:09:51.360 zoology at the University of Hawaii. The paper is called 0:09:51.480 --> 0:09:56.400 Mucus envelope formation in two species of Hawaiian parrotfishes, and 0:09:56.440 --> 0:09:59.720 the paper begins by citing previous research by Win and 0:09:59.760 --> 0:10:03.560 co authors on parrotfish from the coral reefs of Bermuda, 0:10:04.160 --> 0:10:08.079 which were observed to make mucus envelopes at night. So 0:10:08.280 --> 0:10:11.520 when and a co author named Bardak argued that the 0:10:11.559 --> 0:10:16.040 purpose of the mucus cocoon of the slimesack was to 0:10:16.160 --> 0:10:21.520 protect the parrotfish from predators while it was sleeping. And 0:10:21.559 --> 0:10:25.000 this is a hypothesis that I've seen repeated in a 0:10:25.080 --> 0:10:29.840 number of sources that maybe somehow the mucus covering will 0:10:29.840 --> 0:10:33.199 help alert the fish more quickly if a predator gets 0:10:33.240 --> 0:10:36.080 close to it, or may in some way help mask 0:10:36.280 --> 0:10:40.080 the fish, maybe mask the fish is sent from predators, 0:10:40.520 --> 0:10:43.160 or provide some kind of benefit along those lines. 0:10:43.640 --> 0:10:46.960 Okay, So, either to some degree a cloaking system, a 0:10:47.000 --> 0:10:49.720 cloaking device, if you will, or perhaps some sort of 0:10:49.760 --> 0:10:52.600 like added security trip wire made out of mucus. 0:10:53.200 --> 0:10:55.360 There you go. Now, we'll get to another explanation in 0:10:55.480 --> 0:10:57.120 just a bit here, but we're not there quite yet. 0:10:57.160 --> 0:10:59.800 First we're gonna look at like and how and when 0:10:59.840 --> 0:11:02.959 the things form. So the author of the study, John Burn, 0:11:03.440 --> 0:11:07.680 begins by investigating envelope formation in a couple of different 0:11:07.720 --> 0:11:11.800 species of parrotfish. There's scas dubious, commonly known as the 0:11:11.840 --> 0:11:17.720 regal parrotfish, and scas per pair. Oh wow, here's a word, 0:11:17.840 --> 0:11:22.000 pers bisilattis there you go, which is commonly called the 0:11:22.080 --> 0:11:25.880 spectacled parrotfish. Both are found in the reefs around Hawaii, 0:11:25.920 --> 0:11:28.960 and I think the spectacled parrotfish may be one of 0:11:29.000 --> 0:11:32.280 the keyfish referred to as oohu and some of the 0:11:32.320 --> 0:11:35.440 Hawaiian legends that we talked about in the last episode. 0:11:35.760 --> 0:11:37.920 Yeah yeah, So Burn. 0:11:37.920 --> 0:11:40.960 Did some experiments on these two species in his laboratory, 0:11:41.400 --> 0:11:45.880 varying conditions of light and darkness within their aquaria, making 0:11:46.000 --> 0:11:50.280 observations of behavior, and then examining the mucus producing organs. 0:11:50.640 --> 0:11:55.839 So previous field observations had found that as daylight intensities decrease. 0:11:55.880 --> 0:12:00.520 As daylight goes down, fewer parrotfishes can be founding around 0:12:00.559 --> 0:12:04.520 the reefs. For the night time, these fish will disperse 0:12:04.559 --> 0:12:07.680 their schools and go into recesses within the reef to 0:12:07.840 --> 0:12:11.199 hide and sleep, and that's where they generate these cocoons. 0:12:12.320 --> 0:12:15.679 Within the lab environment, Burne found that if you shine 0:12:15.679 --> 0:12:19.200 a constant light on these fish for twenty four hours straight, 0:12:19.640 --> 0:12:22.280 they will actually never make a mucus cocoon. You just 0:12:22.400 --> 0:12:24.480 keep shining the light on them, at least for twenty 0:12:24.480 --> 0:12:27.480 four hours't He didn't push the experiment to go that 0:12:27.600 --> 0:12:30.680 much longer because you know, it might just end up 0:12:30.679 --> 0:12:33.520 harming them overall. But for twenty four hours straight you 0:12:33.559 --> 0:12:36.439 shine a light on them and it, you know, nothing happens. 0:12:36.720 --> 0:12:38.160 Yeah, corp, of course, I mean there are a lot 0:12:38.200 --> 0:12:41.000 of things I'm not going to do of some sort 0:12:41.000 --> 0:12:45.319 of an intelligent being from a highly advanced species shines 0:12:45.440 --> 0:12:47.760 artificial light on me for twenty four hours. 0:12:47.600 --> 0:12:49.920 That's right. So the constant light means he never make 0:12:49.960 --> 0:12:53.120 a pod. However, when darkness was introduced, you turned the 0:12:53.200 --> 0:12:57.120 lights off. This triggered twenty two of the thirty parrot 0:12:57.120 --> 0:13:00.760 fish tested to build mucus envelopes, and it was the 0:13:00.800 --> 0:13:04.960 same frequency in the two different species. The fish took 0:13:05.080 --> 0:13:08.439 different amounts of time to finish building their envelopes after 0:13:08.480 --> 0:13:11.560 the light was turned off. The minimum was like thirty minutes, 0:13:11.640 --> 0:13:14.920 maximum was two hundred and forty minutes. Average building time 0:13:15.120 --> 0:13:19.439 was about seventy minutes. However, if you kept the fish 0:13:19.559 --> 0:13:22.200 the parrotfish in the dark after it made its cocoon, 0:13:22.920 --> 0:13:25.320 it did not stay in the cocoon forever. Eventually it 0:13:25.320 --> 0:13:29.320 would emerge on its own. So what did they do 0:13:29.400 --> 0:13:32.679 when they made these things? They would typically rest their 0:13:32.720 --> 0:13:36.600 bodies on the floor of the tank and the seafloor 0:13:36.640 --> 0:13:39.560 in the wild, in an upright position, almost always with 0:13:39.679 --> 0:13:43.120 one side of the body resting against a vertical surface 0:13:43.240 --> 0:13:45.520 like a rock or a coral wall, or, in the 0:13:45.520 --> 0:13:48.840 case of the lab experiments, the aquarium wall. And then 0:13:48.880 --> 0:13:52.800 the cocoon begins. It begins formation at the front of 0:13:52.840 --> 0:13:57.640 the fish around its mouth, and folds of mucus slowly 0:13:57.760 --> 0:14:01.720 move back along the length of the body toward the tail. 0:14:01.760 --> 0:14:06.439 Though interestingly, the mucus never completely closes over the body. 0:14:06.800 --> 0:14:09.360 There is always at least a one to two centimeter 0:14:09.559 --> 0:14:12.400 gap at the back end of the bubble, and Burn 0:14:12.520 --> 0:14:17.320 believes this hole is to evacuate respiratory water that's forced 0:14:17.320 --> 0:14:21.920 out of the buckle cavity, so sort of a breathing hole. Now, 0:14:22.040 --> 0:14:24.000 I mentioned that in a lot of these photos, the 0:14:24.040 --> 0:14:27.400 mucus cocoon seems to sparkle as if it is covered 0:14:27.400 --> 0:14:31.640 in glitter. Burn writes that quote fine debris adhered to 0:14:31.680 --> 0:14:36.720 the envelope's exterior and the outline was thus more clearly defined. However, 0:14:36.760 --> 0:14:39.560 he says this coating of sediment and debris makes the 0:14:39.600 --> 0:14:42.840 bubble appear thin and delicate. This is how A Wind 0:14:42.960 --> 0:14:47.520 described it in that article from the fifties. But Burn 0:14:47.680 --> 0:14:52.280 did an experiment by injecting pigmented particles into the cocoon 0:14:52.920 --> 0:14:56.160 and revealed that actually appearances can be deceiving here because 0:14:56.200 --> 0:14:59.440 the cocoon often does look very thin, it's like a 0:14:59.440 --> 0:15:04.440 wispy spider web or this very very thin kind of 0:15:04.440 --> 0:15:07.320 gossamer like material. But in fact he found when he 0:15:07.520 --> 0:15:11.320 injected the pigmented particles in there, the mucus structure was 0:15:11.480 --> 0:15:14.600 up to six centimeters thick in some places, so it's 0:15:14.680 --> 0:15:16.120 not as wispy as it looks. 0:15:16.520 --> 0:15:18.400 Okay, this would just be the case of there being 0:15:18.480 --> 0:15:23.280 like a thin layer of particles on top of this 0:15:23.760 --> 0:15:28.280 otherwise translucent or semi translucent mucous shielding. They would give 0:15:28.280 --> 0:15:30.640 it the appearance of being super thin when in fact 0:15:30.680 --> 0:15:32.200 it is probably thicker. 0:15:32.480 --> 0:15:36.240 That's right. So dissection of the fish revealed that the 0:15:37.000 --> 0:15:41.840 presence of gland tissue in the buckle cavity correlated with 0:15:41.960 --> 0:15:44.520 whether or not the fish would make a cocoon. It 0:15:44.600 --> 0:15:47.880 was found that fish that did not have this gland 0:15:48.000 --> 0:15:51.400 tissue in the mouth cavity, they did not form the 0:15:51.440 --> 0:15:56.240 mucus cocoons. So that's how they're made and win. But 0:15:56.280 --> 0:15:59.520 what are they for? Well, again, the burn paper mentions 0:15:59.560 --> 0:16:03.480 this hypothesis that the mucus sleeping bag somehow protects the 0:16:03.560 --> 0:16:08.080 fish from large predators. A commonly mentioned predator in the 0:16:08.120 --> 0:16:10.560 reef environment would be the more eel, you know, and 0:16:10.560 --> 0:16:12.960 it can get down there in the recesses and attack. 0:16:13.560 --> 0:16:17.280 But apparently there's some doubt about this because, for example, 0:16:17.280 --> 0:16:20.480 when faced with reef dwelling predators such as more eels, 0:16:20.880 --> 0:16:24.600 there is some evidence that sleeping fish within within a 0:16:24.680 --> 0:16:29.240 cocoon are still vulnerable, like they still get eaten. But 0:16:29.360 --> 0:16:32.400 actually I came across an interesting twenty eleven paper that 0:16:32.520 --> 0:16:36.000 looked directly into the function of the mucus cocoon and 0:16:36.360 --> 0:16:39.600 came to a different conclusion. So this was published in 0:16:39.640 --> 0:16:43.480 the journal Biology Letters by Grutterer at All and the 0:16:43.600 --> 0:16:46.600 title is this will give some of the findings away fish, 0:16:46.800 --> 0:16:51.800 mucus cocoons the mosquito nets of the sea. This was 0:16:51.800 --> 0:16:55.120 in the year twenty eleven. So in this paper the 0:16:55.160 --> 0:16:59.080 authors look at another hypothesis, which is the idea that 0:16:59.360 --> 0:17:04.680 mucus envelopes actually protect the fish inside from parasites such 0:17:04.720 --> 0:17:11.160 as ectoparasitic nathid isopods. These are these little bloodsucking parasites 0:17:11.200 --> 0:17:15.560 that live throughout the ocean, often compared to terrestrial mosquitoes 0:17:15.640 --> 0:17:19.399 and ticks. Raw I attached to a little photo of 0:17:19.440 --> 0:17:21.159 these things for you to look at. They're kind of 0:17:21.200 --> 0:17:24.200 shrimp like in appearance. Maybe look like a cross between 0:17:24.240 --> 0:17:27.840 a shrimp and a ticky. Yeah, And the authors point 0:17:27.840 --> 0:17:31.680 out that during the daytime when parrotfish are swimming around, 0:17:32.560 --> 0:17:35.640 they actually get some help, they get some protection against 0:17:35.760 --> 0:17:39.159 blood drinking isopods from cleaner fish. You know, this is 0:17:39.440 --> 0:17:42.320 a relationship where a smaller fish that wants to eat. 0:17:42.359 --> 0:17:46.440 These parasites will come along and help pick them off 0:17:46.560 --> 0:17:49.960 to sort of groom the outside of the larger fish. 0:17:50.240 --> 0:17:54.240 But how do the fish protect themselves at night? The 0:17:54.320 --> 0:17:57.600 idea behind this experiment was that maybe the mucous cocoon 0:17:57.680 --> 0:18:01.600 functions like a mosquito net to protect the sleeping fish 0:18:01.720 --> 0:18:07.080 from these heimatophagous parasites. So they tested this hypothesis on 0:18:07.240 --> 0:18:11.960 the coral reef parrotfish Chlorurus sortied us. And the way 0:18:11.960 --> 0:18:13.720 they tested it was they got some of these fish, 0:18:13.760 --> 0:18:17.000 they separated them into groups that would sleep with and 0:18:17.160 --> 0:18:20.760 without the benefit of cocoons in the presence of these 0:18:20.840 --> 0:18:24.119 isopod parasites. And actually, the way they did it was 0:18:24.160 --> 0:18:27.800 they took a subset of cocoon fish and found a 0:18:27.800 --> 0:18:30.040 way to sort of gently push them out of their 0:18:30.119 --> 0:18:35.680 envelopes without waking them up. So what do they find. Yes, indeed, 0:18:35.760 --> 0:18:40.040 the fish without the mucus bag experienced way more attacks 0:18:40.080 --> 0:18:43.919 by parasites. How much more, Well, about ninety five percent 0:18:44.000 --> 0:18:47.879 of the fish without cocoons were attacked by isopods and 0:18:47.920 --> 0:18:51.200 only about ten percent of the fish with cocoons were attacked, 0:18:51.359 --> 0:18:53.040 So huge difference. 0:18:53.000 --> 0:18:55.160 All right, Right, So Yeah, coming back to the mosquito 0:18:55.240 --> 0:18:58.119 net comparison, it's like, initially we looked at it and 0:18:58.200 --> 0:19:01.160 we're like, this mosquito net must protect the sleeper from bears, 0:19:02.160 --> 0:19:06.280 but in reality it protects them from mosquitos and similar 0:19:06.280 --> 0:19:07.280 insects that sort. 0:19:07.160 --> 0:19:12.000 Of thing, or maybe even something downstream from mosquitoes in 0:19:12.080 --> 0:19:15.560 the analogy here, because the author is also investigated the 0:19:15.640 --> 0:19:20.200 question of how energetically costly it is for the fish 0:19:20.240 --> 0:19:23.520 to make these mucus orbs, and they calculated that it 0:19:23.560 --> 0:19:26.760 takes about two point five percent of a fish's daily 0:19:27.040 --> 0:19:31.000 energy budget to make the mucus bag. Now, when I 0:19:31.359 --> 0:19:33.600 first saw that figure, I kind of thought, oh, hey, 0:19:33.640 --> 0:19:37.000 that seems fairly cheap, only two point five percent. But 0:19:37.119 --> 0:19:40.040 actually I was reading some news reporting on this that 0:19:40.160 --> 0:19:44.600 quoted the lead author, Alexandra Grutter, and she framed it 0:19:44.640 --> 0:19:47.080 a different way. She said, quote, the amount of effort 0:19:47.160 --> 0:19:50.080 that goes into building these cocoons, which requires fish to 0:19:50.160 --> 0:19:52.960 have developed very large glands about the size of a 0:19:53.080 --> 0:19:58.359 quarter to produce the cocoons, is extraordinary. Parasites must exert 0:19:58.400 --> 0:20:01.359 an enormous pressure on these fish in order for the 0:20:01.359 --> 0:20:04.240 fish to have evolved such a specific way. Of avoiding 0:20:04.320 --> 0:20:07.600 the parasites. So what could be so pressing? Is it 0:20:07.680 --> 0:20:09.720 really just that you don't want to get bitten by 0:20:09.720 --> 0:20:13.040 these isopods and have them drink some of your blood. Well, 0:20:13.240 --> 0:20:17.680 Grutterer mentions the possibility that the blood directly lost to 0:20:17.720 --> 0:20:21.640 the parasite might not be the only cost. These isopods 0:20:21.760 --> 0:20:26.920 may also transmit a secondary endo parasite which lives in 0:20:27.000 --> 0:20:32.400 the fish's blood, much like how mosquitoes transmit malaria in humans. 0:20:32.920 --> 0:20:36.080 So the mosquitoes themselves are annoying and you don't like 0:20:36.119 --> 0:20:39.960 the mosquitoes, but the malaria is much more concerning than 0:20:40.040 --> 0:20:43.440 the mosquito. Malaria can be deadly. So in a similar way, 0:20:43.480 --> 0:20:46.800 it's possible that it's worth it for these fish to 0:20:46.920 --> 0:20:52.640 build these slimy bionets to protect themselves from blood disease. Wow, 0:20:53.119 --> 0:20:55.439 so it seems like a good trade. You spend a 0:20:55.440 --> 0:20:58.920 little energy to weave a slime tube before bed every 0:20:59.000 --> 0:21:03.640 night without these tiny shrimp monsters drinking your blood possibly 0:21:03.680 --> 0:21:06.920 giving you diseases of the blood, and it all works out. 0:21:07.040 --> 0:21:09.359 And in fact, there was one more observation from grutter 0:21:09.760 --> 0:21:14.520 speaking to the media that kind of maybe there's a 0:21:14.560 --> 0:21:18.879 strategy to recoop some of that nightly cost. So Grutterer says, quote, 0:21:18.920 --> 0:21:22.040 I have observed on occasion a fish at dawn with 0:21:22.080 --> 0:21:26.560 what appeared to be mucus stuffed in its mouth. And 0:21:26.600 --> 0:21:28.639 then she goes on to say she has seen other fish, 0:21:28.680 --> 0:21:32.480 not parrotfish, but related fish that also produce mucous cocoons 0:21:33.720 --> 0:21:37.199 pecking it at its old cocoons in the morning. So 0:21:37.359 --> 0:21:40.840 like recooping some of that nightly cost by eating the 0:21:40.960 --> 0:21:42.960 mucus that you created before bed. 0:21:43.320 --> 0:21:45.879 I mean, that's just it's economically sound. It's like if 0:21:46.000 --> 0:21:50.600 humans produce, say an ectoplasm defense shield at night, you 0:21:50.640 --> 0:21:53.240 would want to to recoop that cost, and that might 0:21:53.320 --> 0:21:55.760 mean consuming all that ectoplasm again and getting all that 0:21:56.560 --> 0:22:00.399 liquid back into your body. You know. It reminds us 0:22:00.440 --> 0:22:04.440 of other examples we've looked at in biology, such as 0:22:04.640 --> 0:22:08.760 various reptiles that will eat their own shed skin because 0:22:08.920 --> 0:22:10.439 you know, why waste that, you know. 0:22:10.600 --> 0:22:14.200 YEA, so may still provide some kind of benefit against 0:22:14.520 --> 0:22:19.159 larger macroscopic predators too. Not certain about that, but it 0:22:19.200 --> 0:22:21.400 does seem like there's a very good case that these 0:22:21.480 --> 0:22:24.800 mucus bags help prevent against parasite attacks. 0:22:24.920 --> 0:22:38.000 Very fascinating, all right, and so for the rest of 0:22:38.040 --> 0:22:40.280 the episode, we're going to turn to the world of 0:22:40.320 --> 0:22:45.000 parrotfish reproduction and parrotfish sex. So, as we teach out 0:22:45.000 --> 0:22:48.040 in the first episode, one of the other amazing aspects 0:22:48.080 --> 0:22:53.040 of parrotfish biology broadly is that they change sex during 0:22:53.040 --> 0:22:56.520 the course of a normal lifetime. That's to say, this 0:22:56.640 --> 0:22:59.520 is not something that occurs, you know, only when certain 0:22:59.600 --> 0:23:03.199 environments conditions are right. It occurs as part of a 0:23:03.320 --> 0:23:05.000 normal life cycle. 0:23:05.119 --> 0:23:07.640 And within a fairly predictable pattern, right. 0:23:07.760 --> 0:23:10.080 That's right. Yeah, And they're going to be a couple 0:23:10.119 --> 0:23:12.479 of exceptions. Again, as we've been distressing, there are a 0:23:12.600 --> 0:23:18.399 number of different species of parrotfish, but still the vast 0:23:18.400 --> 0:23:23.520 majority of them do follow this example that we're going 0:23:23.560 --> 0:23:29.200 to be discussing. So they are proto gynos that means 0:23:29.240 --> 0:23:34.600 female first, hermaphrodites that always turn into males if they 0:23:34.640 --> 0:23:37.480 live long enough. So they're born female, and then at 0:23:37.480 --> 0:23:40.760 a certain point during their development they become male and 0:23:40.840 --> 0:23:43.119 live out the rest of their life as a male. 0:23:43.400 --> 0:23:45.920 And this would feed back into something we talked about 0:23:45.920 --> 0:23:49.680 in the first episode, which is sometimes difficulty in identifying 0:23:50.200 --> 0:23:54.200 parrotfish species because they undergo these changes, and these changes 0:23:54.240 --> 0:23:56.840 come with changes to their outer appearance. 0:23:57.080 --> 0:24:00.280 That's right. Along the way, multiple changes in colorization take place, 0:24:00.680 --> 0:24:03.080 some of which have to do with just aging, some 0:24:03.160 --> 0:24:06.240 of which have to do with changing their sex, and 0:24:06.400 --> 0:24:11.119 others that have to do with diet and other factors. 0:24:12.480 --> 0:24:16.199 This pointed out by the National Marine Sanctuary Foundation as 0:24:16.200 --> 0:24:20.160 some resources about the parrotfish. I also want to point 0:24:20.200 --> 0:24:24.719 out though, that according to NAA fishery biologist Ronald J. Saals, 0:24:25.080 --> 0:24:28.120 gonecharism has been reported for I think three species within 0:24:28.160 --> 0:24:30.959