I’ve had a sucky week. I know you might not see this for a while but can I please have some weird animal facts when you get a chance to answer? :]
I’m sorry your week sucked, have some TURTLES.
Behold: one of nature’s best examples of min-maxing.
Armor plating isn't uncommon in vertebrates. Pangolins, ankylosaurus, armadillos, and placoderms all share similar stat allocation to name a few.
Some, like pangolins, just throw all the keratin they can into their skin and end up with tough scales. That's the same stuff fingernails and hair are made of, and also the stuff that makes our skin waterproof. Others, like ankylosaurs, also grow little bits of bone into their skin. A bunch do both. These are common, efficient, easy-to-evolve traits that occur multiple times in history.
Turtles said fuck all that.
(Well not ALL that, they do still have keratinized scaly skin on their limbs, but still)
They took their rib cage, sternum and spinal column- you know, things that normally go inside your body, and put 'em on the outside instead. Shoulder blades and hip bones grow inside the rib cage, too. Then, as if that wasn't enough, they covered the whole deal in keratin scales. Some turtles even have a hinge on their belly (plastron) that lets them close up completely. I promise, there's a turtle in there.
What could go wrong reverse-engineering an exoskeleton onto a vertebrate?
Take a nice deep breath in, and exhale it out. Can you feel your ribs move? Feel them expand and contract, working with your diaphragm muscles to pull large quantities of air into your body?
Yeah, when all your ribs are fused into one big dome it turns out you lose a lot of lung function. The good news? With your body fully enclosed and stabilized in bone, it's not like your abs and obliques are doing anything now. Might as well put them to work pumping your lungs. Except, not directly. Some muscles pull on the liver, which attaches to the right lung. Other muscles pull on the stomach, which pulls on the left lung. It’s pretty inefficient all around, so you may not get enough oxygen exchange to be a marathon runner, but as long as you don't have to worry about predators you know what they say about slow and steady.
However that's not always enough. What if, say, you did have to worry about predators a little. What if, hypothetically, you took a few points away from pure defense and gained a little more swim speed and mobility? You, like many semi-aquatic turtles, would need a backup source of oxygen. A breathing plan B.
In turtles, plan “B” stands for Butt. Some turtles (lots of freshwater semi-aquatic ones) can pump water in and out of their cloaca, which is sometimes enlarged and lined with specialized membranes that maximize surface area for gas exchange. Basically, improving any part of this fucked-up breathing apparatus is so difficult that it’s evolutionarily better to evolve proto-gills in the ass.
I was going to make a different joke here but these turtles are literally called “Northern Red-Bellied Cooters” and I really can’t top that
Turtles are cold-blooded, which of course means they don’t do shit in the winter. Turtles who are unfortunate enough to live in places that get winters bury themselves in the mud in a type of hibernation called ‘brumation’. You may wonder, how do they breathe THEN?
Easy, they don’t. They slow down their metabolism a crazy amount and spend the winter months doing anaerobic respiration. We can do this too, it’s why your muscles burn after working out. If your body doesn’t get oxygen, your cells can still burn fuel much less efficiently and produce a lot of lactic acid as a byproduct. Turtles can counteract the extreme acidity, buffering it and sequestering it with the bone in their shell. Literally, they leach calcium and magnesium out of their bones to prevent their acidic blood from killing them over the winter.
Just waking up from the winter, chock-full of acid and ready to snap.
The most infuriating thing, personally, is that all of this bullshit min-maxing works. Turtles are the longest-lived land vertebrates. The oldest recorded one lived to 187. There’s a little box turtle at my workplace that’s almost 90. This isn’t a glass cannon like a horse is, this janky tank build WORKS.
