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Today on Animal Fact Files we’re talking about flatfish. You can subscribe to stay up to date on new releases! Mr. Slugstar requested these flatfish so let’s get into it. Technically speaking, we’re going to talk about all kinds of flatfish today, but “flounder” has better seo and technically all flounders are flatfish so we feel like it counts. Not all flatfish are flounders, however, so the other kinds of flatfish that will appear in this video include halibuts, turbots, soles, and all other kinds of flatfish. I swear we don’t make this stuff up.

Flatfish are pretty distinct. They’ve broken the rules of symmetry within nature, and thus appear like some strange cross between a normal fish and a stringray. Flatfish are believed to have developed this way from fish long ago that would hide from predators by laying on one side of their body on the bottom of the ocean. Eventually, their eyes started to shift and flatfish became permanent bottom dwellers - but they don’t start out this way. Flatfish hatch from eggs that are fertilized via spawning. Depending on the species the eggs may float to the water’s surface or sink to the bottom, but when the baby flatfish emerge they look like your everyday regular fish. Give them a few weeks, however, and things begin to look a little… fishy. One of a flatfish’s eyes begins to migrate across its face to join up with the eye positioned on the other side of its body. During this transformation, even the flatfishes skull will change in shape. The side of the flatfishes body that will become blind will slowly fade to white in color, and the side with both eyes, which ultimately becomes the flatfish’s topside, takes on the color of its environment.

Flatfish live on the bottom of their watery habitat and use camouflage to blend in with their surroundings. They can be almost impossible to see once they’ve taken on the correct color pattern. This blending in is perfect for avoiding predators, but also for ambushing prey. Flatfish eating other fish, crustaceans, cephalopods, and worms. Flatfish catch their meals by using the fin located on the underside of their body and pushing off of the seafloor while releasing a burst of water from their gills. They can move quick, and their prey doesn’t stand much of a chance. It’s actually thought this is part of the reason flatfish start out looking like normal fish. If they were born with those crazy bodies and lived on the bottom of the ocean with their parents, their parents might just gobble them up on accident (or on purpose). It’s the same idea as to why leaf eating caterpillars metamorphose into nectar eating butterflies; there’s less competition.

There are more than 500 species of flatfish living in waters throughout the world. They can be found in the ocean, but they’re also able to survive in freshwater, as well. The size of a flatfish largely depends on the species. Some are just a few inches long, while others, like Atlantic halibut, can grow to be seven feet in length! Now that’s a lot of fish! They’re eaten by humans, other fish such as cod and bass, birds such as egrets, and mammals like sea lions. Even though their eaten by many different animal species, one kind of octopus actually mimics the way flatfish swim to avoid predation. If you think about it, a single octopus leg is way easier to catch than an entire, hard-to-see fish

Flatfish were once used as an example to oppose Darwin’s theory of natural selection. It was argued that there were no transitional fossils of the fishes and that the transitional period wouldn’t offer any benefit to the individuals going through it. However, more recently a transitional fossil has been identified as an ancestor of flatfish and thus Darwin’s fears of his theory being ruined by this weird fish were actually unfounded!

For more facts on flatfish, check out the links in the description. Once while snorkling we found a juvenile flatfish; have you ever seen one in the wild? Give a thumbs up for weird fish, and thanks for watching Animal Fact Files!