Marine Biologist Answers Fish Questions From Twitter ｜ Tech Support ｜ WIRED

I'm Professor Corey Evans. I study fishes. Let's answer some questions from the internet. This is Marine Biology Support. At Gabe Savage 6 asks, is finding Nemo an accurate representation of ocean life? Yes and no. One thing that they did get right is that clownfish do in fact live in anemones, and they are in fact immune to the stings of the anemones. One thing that is pretty different is that clownfishes actually can change their sex. So in the movie, Nemo's mom gets eaten. And in real life, after a female clownfish is eaten or dies, the largest male will then become the female. So Marlin in Finding Nemo would have actually become a female clownfish and laid his own clutch of eggs within probably the next week or two. So another thing that's different is Bruce the shark. So in the movie, Bruce the shark is a male shark, but if you look close, Bruce the shark does not have claspers. Claspers are the male intermittent organ that sharks have. They're on the pelvic fins. They're basically two very long penises. Clear as day. And Bruce doesn't have them. So Bruce is technically maybe a female shark. At DoG's Move Silent asks, why is white sand different from brown? White sand is generally derived from the shells of other animals. Shells get broken down either via wave action or via animal feeding. And brown sand is different in that it's typically the result of rocks that have been eroded over time. Most of the white sand comes from a very unlikely source, and that is parrotfishes. They feed on coral skeletons, and when they excrete it, they excrete it as this nice white fine sand. So much of the white sand that you see is derived from parrotfish poop. A single pair of fish can produce 450 kilograms of sand per year. So that's a lot of poop. That's a lot of sand. At Myer Nguyen asks, how do schools of fish swim in harmony? So in order to answer that question, we have to talk about the sensory systems of the fish. So all fishes, for the most part, have what we call a lateral line structure, which is a long line that runs from head to tail, and it's covered with what we call mechanoreceptors. These are little hair cells that can sense changes in water pressure. This is why if you ever try to catch a fish with your hand, even if it's looking away from you, it generally gets away from you. And that's because when you put your hand in the water, you push water towards these lateral line cells, and the fish knows where you are without even looking. Typically in a fish school, one fish will generally respond to the movements of the fish that's right next to it. So as this fish moves, it's going to push water towards the lateral line of that fish. And if you repeat that over a really large scale, that's how you get these really nice, harmonious, and synchronized movements across fish schools. Swimming in schools makes it easier to move through water. Water is what we call highly viscous. So when you have something in front of you that's breaking up kind of the flow and distribution of water, it makes it easier for the thing behind it to swim. The short answer is, they don't want them there. They're trying to move the boats out of the way, and the boats generally disturb their marine environments. Humans generally have a very long history of messing with whales, especially from boats. Humans basically wiped out most of the whale populations in the Atlantic via these whaling boats. The unique thing about orcas is that orcas kind of have culture like humans do. They have the ability to transmit information to subsequent generations without having to pass it on through their genes. Some orcas actually do have fashion. There was a trend where one orca started wearing a fish as a hat, and later on, the other orcas in the pods also started wearing fish hats. And then this fashion actually jumped to other pods of orcas also trying on the fish hat craze. No Google needed. The fastest sea creature in the ocean is the sailfish. These fish can get up to 50 miles an hour. Many of the fastest sea creatures happen to be warm-blooded, or what we call endothermic. Tunas are famously warm-blooded. These animals are also high-speed swimmers, about 40 miles an hour for a tuna. All shells come from animals, generally invertebrate animals that basically lay these down as protection. And things like this conch shell, which is actually the remnant of a very large snail. Marine invertebrates over the past 300 million years have evolved the ability to take in minerals from seawater and their food, limestone or calcium carbonate, and construct them into these very elaborate exoskeletons. Sometimes you'll find shells that have holes in the top. This is typically from a marine predator, like boring snails, where they'll actually drill a hole into the shell of this animal and consume it. Some shells are really, really pretty, and you might be tempted to pick them up. One example here is the cone snail shell. But the animal that lives in these is incredibly dangerous. The cone snail is actually a venomous snail. We don't have an antidote for their venom. If they're disturbed, they will shoot a harpoon full of venom into the pocket of the person who's likely put this shell in their pocket. So even though they're beautiful, some shells should stay at the beach. The short answer to this question is to assume the starfish is always hungry, because they most likely are. They are voracious predators. The starfish has no brain, so it doesn't have a centralized decision-making center. However, each arm is packed with sensory structures, and each arm will basically taste the water. And once enough tentacles start pointing towards where the food is, the entire animal will then move its body in that direction. Once a starfish lands on something that it wants to eat, say this clam, for example, it will actually force the shell of that clam open just a little bit, and it will insert its stomach into the shell of the clam. So it will eject the stomach out of its own body into the shell of this clam, where it will then digest the clam inside its own shell, and then draw the stomach back inside of them when they're done feeding. Yes, mantis shrimp and many other aquatic animals have the ability to see far more colors than we can because they have more photoreceptors in their eyes. So mantis shrimp can see well into the UV spectrum. I'm not even sure that this is the craziest thing about mantis shrimp. Some mantis shrimp have the ability to punch so fast, it looks like a flick when they punch, that their actual punch and club tears water molecules apart. And when the water molecules rush in to fill that space that's been created, it causes them to boil at really, really high temperatures. Inside of this little bubble of boiling water, the temperatures can reach and exceed the temperature of the surface of the sun. The short answer is because you didn't evolve in the depths of the ocean, and you don't have to draw your food towards your mouth. So in the anglerfish head, there's a fin at the top that's been transformed into a lure. And in deep-sea anglerfishes, this lure is bioluminescent, so it lights up, and they use it to attract prey. What this anglerfish will do is it'll sit there in the middle of the water column with this light-up lure in front of its face, and fish will come in thinking that it's food, and they will then themselves become food. It's hard to compare intelligence, but I would probably argue dolphins. They have the ability to pass the mirror test, which is being able to recognize themselves in the mirror. Other examples include octopuses. Some octopuses are able to solve maze problems in order to find food. Also, fun fact, many octopuses have the ability to rapidly change their color to match their surroundings. Atjpblow asked, how do octopuses change their color? Their skin actually has the ability to see or perceive the color of the background that they're sitting on, and that information is somehow passed on to the chromatophores that lives underneath the skin. Each chromatophore holds one pigment. There might be a blue pigment, a red pigment, and a yellow pigment. They can rapidly change the distribution of these pigments in their skin. It allows them to rapidly change color, and they have fine-scale control over each of these pigment cells. AtmrmckenzieSD5 asked, how do you tell a fish's age? So fishes generally have indeterminate growth. However, there is a way to tell. This is a 3D-printed fish skull. There are a couple bones in the back of the skull here that are called otoliths. They're underneath the skull, but if you were to pull them out, you'd find these really nice coin-shaped bones that have these concentric growth rings around them. So fishes lay down these growth rings in their bone, much like trees do. So you can actually count the rings in fish bone, much like you would in a tree. AtxoDanny asked, fish fry at my grandma's today. Fish with bones and fish without bones. Yeah, this is how I classify my fish. This is how I classify my fish too. So it turns out, you can actually classify much of vertebrate diversity into these really neat categories of fishes with bones and fishes without bones. All the vertebrates that have jaws can be broken into two distinct categories. So there are cartilaginous fish, which are sharks, stingrays, and the rare chimera. And then there are bony fishes, which include trouts, frogs, cats, dogs, and you and me. Yes, even you and me. Biologists typically classify humans and mammals in general as a group of organisms within the larger clade of bony fishes. AtCPFChanner asked, do all fish have similar numbers slash types of fins? And what are these fins called? Some of the common fins you might see are these pectoral fins off on the side. Pectoral fins in general are often used in hovering behaviors. So you see these in fishes that live in coral reefs. So things like wrasses and triggerfishes will oftentimes flap their pectoral fins to hover over a structure to further investigate whatever is living in it. The fins at the top are typically called dorsal fins. The front dorsal fin is particularly interesting because they oftentimes get adapted into venomous spines, sometimes even fatal in the case of the stonefish. In the case of this little Nile perch, it looks like one continuous dorsal fin, but there's basically a skin connection between the front spiny dorsal fin rays and the back kind of feathery dorsal fin rays. This back fin is called the caudal fin, and it's used to generate thrust if a fish is trying to get away. It'll beat this tail fin to help it move quickly. AtNivWrites asked, does coral count as an animal? It's so alive and so pretty. It is, in fact, an animal, and it's also alive and very pretty. They're closely related to jellyfish, but instead of floating in the ocean, they build these complex limestone skeletons, so you can see these little holes and pock marks inside the coral skeleton, and that's where the individual polyps live. So in life, this coral would be very, very colorful. However, this particular skeleton is bleached. So when corals get stressed because of higher temperatures in the ocean, they'll expel the algae that they keep inside their tissues, and they'll basically have no way to feed, and they'll starve over the course of the next several weeks. Losing these reefs, which can happen very, very quickly, will have catastrophic effects on tropical diversity worldwide. So ways to prevent this include reducing global temperatures, taking climate change seriously in general, and in some very isolated cases, pumping cold seawater back onto the corals. AtElizabethRush asked, how does the goblin shark even eat without its nose getting in the way? Goblin sharks have these very, very elongate rostra, or noses, that they use to sense other animals in the water column. In order to feed, they actually have to protrude their mouth out away from their nose to catch prey and bring it back. If you just try to bite something underwater, you'll actually push it away from you. So many animals have evolved the ability to protrude their mouths and generate suction to bring prey towards them. Another one is the slingjaw wrasse. They have the ability to protrude their jaw up to a third of their total body length to bring in evasive prey, and then retract it. Ad Jameson Rich asked, never forget that there's a creature on this earth that was discovered and named by the people of science, the vampire squid from hell. So yes, vampire squids are real, they are a thing. They were discovered in the late 1890s in the Valdiva expedition. If you dropped a net thinking that there would be no life at the bottom of the ocean and you pulled up that vampire squid, you would name it the vampire squid from hell too. Contrary to their appearance, which can be quite terrifying, these animals have basically made a living out of doing nothing. They live in oxygen minimum zones in the ocean, so they very rarely ever move, and they feed primarily on leftover food that basically floats down from the surface. At Jaquel 8277638 asked, OMG, when did whales learn to walk on land? Whales learned to walk on land about 35 million years ago. So all whales, manatees, and seals evolved from ancestors that once walked on land. These whale ancestors gradually became more aquatic, and as they got larger and as they became more adapted to aquatic habitats, they evolved a broader range and a wider range of dietary strategies. At Stephanie Lino asked, there's no way seahorses are real. Seahorses are quite real. Seahorses have been around for 13 million years, and in that time, they've actually evolved a broad variety of body shapes typically associated with camouflage. There are things like the leafy sea dragon, which looks like a piece of kelp. Seahorses are terrible swimmers, some of the worst. To get around that, they've evolved these prehensile tails that allow them to basically wrap their tails around structures so they can stay put. The seahorse is perhaps most famous for the fact that the male seahorse gives birth. The female will transfer her eggs into the brooding pouch of the male seahorse, and then when the eggs hatch, the male seahorse will actually give birth to the little seahorse babies. At BY Brandon White asked, what is the best defense mechanism in the sea? My favorite defense mechanism in the sea actually happens to be electricity. You see this in torpedo rays and stargazers oftentimes, where if you grab them, you actually be shocked. The way that they are able to shock you is using these modified muscle cells that have evolved to be able to generate an electric current. For some electric fishes, for instance the electric eel, the current can be as strong as 600 volts. The electric eel can drop a horse. But perhaps the weirdest defense mechanism that you'll see in the sea actually comes from hagfish slime. Hagfish slime feels weird. It feels wet, slimy, but also fibrous. So as you pull it apart, it still has some consistency to it. If a shark, for instance, will come and take a bite out of a hagfish, before the shark can even bite down, the hagfish will secrete slime and clove up the shark's mouth and gills, allowing it to make an escape. At MWSRXO asked, what do fish breathe in, water or air? Wow, how do they make bubbles down there? So fish actually breathe oxygen. They bring in oxygen from the water and they extract it with their gills. These gills are really sensitive. They're often one or two cell layers thick. They have to remain really thin to allow for gas exchange. The internal structures here that you can see in the gills are called gill rakers. They'll swim through a school of plankton with their mouths open. And these rakers in the gills will trap the plankton while allowing water to pass through. One way that fishes generate bubbles is through their gas bladder. So some fish, like the, for instance, the dojo loach, actually has the ability to release gas out of its anus to sink further down into the water. At MJDUKWA, it's crazy how sea creatures just know exactly where to go when they migrate. Some marine animals will follow the magnetic field of the earth. Big migrations include the migrations that we see in humpback whales as they move from the tropics, where they give birth and where they breed, to temperate and colder feeding grounds where they'll feed on plankton. Other big migrations include salmon. They grow up in freshwater. They move out to the ocean and then they can return to the stream that they were born in to reproduce. And they accomplish this by following the earth's magnetic field and also tracking the scent of the stream that they were born in. At The Hindu Science asks, what is the diel vertical migration and its role in carbon sequestration? The diel vertical migration is the largest migration on the planet. This occurs every night all around the world, where plankton will actually move up from the depths of the oceans. There's mixing of the carbon dioxide in the air with the water right at the surface. Plant plankton will basically extract carbon dioxide from the ocean and use this carbon to build their bodies. Larger plankton will then come and eat these plant plankton, and then fishes and other animals will come eat the larger plankton as well, and then sink back down to the depths, taking that carbon with them. So it actually ends up being very important for the sequestration of carbon dioxide. At C4A1 asks, do you ever think about what lives in the Mariana Trench and freak yourself out? Yes. The Mariana Trench is the deepest point in the ocean, 36,000 feet deep. It's deeper than Mount Everest is tall. We have actually reached close to the bottom. James Cameron and about six other ocean explorers have taken submersibles down into the depths of the Mariana Trench. At that depth, the ocean reaches pressures that would basically crush us instantly if we ever went down there. But many animals have evolved to actually live there. In order to do so, vertebrates have generally reduced their bony skeletons. You probably wouldn't find a megalodon at the depths of the Mariana Trench, because megalodon actually evolved to live in shallow tropical waters like in the Bahamas, but you might find some weird clams. At C22Hancho asks, how do these bioluminescent waves work? Do people just throw glow sticks in there or what? These bioluminescent waves are widespread around the world. You can find them in places like Puerto Rico. You can also find them off the coast of the Pacific Ocean. They're produced by plankton, and whenever plankton are startled or disturbed, they'll release bioluminescence to disorient predators. So they'll have little openings in their exoskeletons that allow for light to be produced. At NekoBK asks, y'all knew jellyfish are immortal? Like them bitches don't die? Ever? Turns out, some jellyfish are in fact immortal. The immortal jellyfish, so aptly named, has the ability to revert back to its juvenile stage. If it's ever injured or starving, it will then later produce a genetically identical clone of itself to further perpetuate itself. Other animals in the ocean are famously long-lived. The Greenland shark is a great example. These animals can reach 600 years. Many of our large whales can live for hundreds and hundreds of years. There are still whales out there today that have the old harpoons from harpoon ships still embedded in them. Some lobsters can get pretty close to being immortal. Whenever a lobster grows, it actually has to shed its shell. They're very vulnerable during molting process because their soft parts are basically exposed, and many animals are really queued in to find crustaceans that are molting. Especially once they get older, it gets harder to escape that molting shell. So a lobster that's been alive for, you know, 150 years might finally die by, at last, being unable to escape that shell. The estimates for lifespan are technically indefinite because if nothing eats them, they can just keep going. At HannahXGirl, I need to know why evolution keeps making crabs. So we don't know why things keep turning into crabs, but things that are not crabs keep turning into things that look like crabs. An example of an animal that has evolved into a crab is a hermit crab. Hermit crabs are not true crabs. If you're trying to picture what a hermit crab looked like before it became a hermit crab, it most likely looked quite a bit like a shrimp or a very skinny lobster. So over the course of tens of millions of years, these hermit crab ancestors began to roll their tails up and project them at weird angles, and also enlarge their claws, and eventually came to resemble the crabs that we know today. At IamWinter asks, fishes don't have eyelids, so do they ever sleep? The answer to that is yes. During the sleeping process in fishes, part of the brain shuts off, but they're still able to breathe, so you can still see their gill flaps moving. They have reduced response to stimuli, so you can swim up and basically touch a sleeping fish in many cases. In the case of whales, the pattern is very much the same. Part of their brain tells them to go up and take a breath of air, and then they'll do that, and then they'll come back down, all while sleeping. Sperm whales are really famous for this because they sleep vertically in pods. You can stumble upon a pod of sleeping sperm whales that look like big, tall forests in the middle of the ocean. So those are all the questions for today. Thanks for watching Marine Biology Support.