[Intro]

Whether you like it in your tacos, fried with chips, or on a top of rice, fish can be delicious. But, if you've ever eaten it, you probably noticed how flaky fish can be. Poke at it with your fork and it just falls apart, no knife required. Other meats, like beef or pork, don't break up into those little chunks, either.

It turns out that the same muscle physiology that helps fish get around underwater ultimately means better tacos for us. Fish bodies are ridiculously muscular compared to land animals. Cows may look like tanks made of beef, but muscle makes up less than half of their body mass; while in salmon or tuna, it can be over 60%.

And, almost all of that is fast-twitch muscle, which is exactly what it sounds like: muscle that contracts quickly and forcefully. That's a pretty handy adaptation if you need to quickly swim away from predators. In contract, land mammals tend to have much large proportion of slow-twitch muscle fibers to support their bodies during hours of standing and grazing. 

But, even when land animal tissues have lots of fast-twitch muscle, like a turkey breast, it doesn't flake like salmon; it shreds. That's because land animals organize their muscle fibers into fascicles, long bundles wrapped in connective tissue. Fish instead have overlapping layers called myomeres, w-shaped segments that interlock with each other and allow the fish to bend its whole body side to side as it swims. It's these layers that create the chunks that break apart when you poke them with a fork.

Myomeres are wrapped up a bit differently, too. All animal muscle contains some connective tissue called collagen, but, bite for bite, fish meat has less collagen that its bovine counterparts. Collagen binds myomeres together, and you can sometimes see it as white stripes in a cut of fish.

Fish collagen also breaks down at a much lower temperature compared to that of land animals, due to different amounts of an amino acid called hydroxyproline. This is fine when the fish are in their comparatively chilly habitat, but it makes a big difference in your frying pan. All that collagen becomes gelatinous when heated, which causes it to fall apart more easily.

So, not only is fish muscle organized into chunks on the animal, but the connective tissue it's wrapped in disintegrates more easily before it gets to our forks. If all this makes you look at fish a little differently, allow me to recommend the fried version. You can't see the flakes and it goes great with sriracha. 

Thanks for watching this episode of SciShow, and a huge thanks to our President of Space, Matthew Brant, for your support. If you're interested in joining our community of patrons and maybe becoming the next President of Space, check out Patreon.com/SciShow.

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