I TYPED A RESPONSE. IT IS LITERALLY A SHORT, RAMBLING, DISORGANIZED ESSAY OF 1300 WORDS ABOUT TROLL BIOLOGY, AND IN THIS ESSAY, YOU WILL SEE MY TRUE FACE. I HOPE TO GOD THE READMORE WORKS. If this interests you but you can’t figure out what the fuck this is, it starts here, which is followed up in a slightly irritated tone here. THEN it’s siadea’s post which ought to be read too, don’t skip over it. I think all of this is extremely cool, and I hope it’s not too dry or hard to understand for people who are not the most biologically inclined, because IT’S REALLY COOL YOU GUYS, evolution and adaption and shit is just so cool and I love it so much. Like goddamn there is nothing in this world I adore more than this and I finally have an excuse to vomit it all over tumblr and wow this is just a tiny piece I could go on forever please just read this.
I’d placed Glb’golyb in the lower regions of the twilight zone mostly for Feferi’s benefit. Whether she’s actively pulling the carcass down or just defending it against other scavengers as it sinks, the journey would be long and difficult on her body, so it would be best to minimize the amount of time she had to spend diving. Detritivore does describe her very well though, and yeah, logically she probably should be lower.
It did occur to me after reading what you wrote that she might stay inside the body of the whale as it descends so that she doesn’t need to spend much energy actually diving. Feferi does not tow the whale, the whale tows HER, in its gut. The wound is what most scavengers would be drawn to anyway, so to protect it she would need to hang around those areas. That also takes care of any drag and buoyancy problems she may have, and to an extent temperature as well—an animal doesn’t lose all heat immediately after they die, so by resting near the core of the carcass she would be able to stay warmer for longer, and only has to deal with the full brunt of low temperatures for the return trip.
One thing we have to keep in mind is that seadwellers aren’t a separate species. Whatever they have, their terrestrial counterparts also have or have had in an earlier stage of development. Seadwellers should be better adapted to amphibious life in salt water, but they can’t have completely new systems or ways of doing things.
Oily liver, more yellow marrow in the bones and muscles closer to the body core are all plausible and good ideas though!! And I think lightweight cartilage is good too, but I think that’s something that would probably apply to the species as a whole, not just seadwelling folks. I am hesitant to say that they are coldblooded though, partially because landdwellers would likely be the same, and also that they are strictly nocturnal so they wouldn’t have sunning behaviour or anything to heat themselves, and they’d be rather slow and sluggish in general. Heterotherm means something a LITTLE different so mostly I’m just harping on a funny word choice—heterotherm makes sense, but again, I think landdwellers also should have the same ability (seadwellers are just better at it and make use of it more). That adaption might also have super interesting evolutionary & geographical implications, because it COULD mean that they hibernate, or that’s what ancestral species did. AND THAT’S CRAZY because we know they tend to live near water and we also know what their planet looks like. It’s a single massive northern continent and a single massive southern ocean which means most life will be concentrated near the coast/the tropics. The comic depictions of the characters’ hives totally support this too. Therefore if they needed to hibernate at one point in time… that means they would have probably originated way up in inhospitable northern desert areas, there’s no reason to hibernate at the equator. But I also think that their origins are from the sea (I will explain in a minute) so there is a bit of a problem there! UNLESS. Unless there used to be sea in the north too, but it dried up entirely. Why?? Are they actually in the middle of an ice age?? Was there some sort of catastrophe up there that managed to totally fuck up the planet?? There are a lot of cool questions to wonder about.
But now I want to talk about chitin! Chitin, bone and developmental anatomy, because that’s the part of the post that stood out most to me.
In dialogue they did mention chitin. Chitinous windholes to be precise, in a derogatory context where it could mean something like primitive/trogdolytic/babyish. So I’ve taken it to mean that chitin is something they do actually make use of, probably in stratisfied squamous epithelium, and it probably plays a more visible role in grubs. Also, that grubs are notoriously stupid creatures, way beyond how stupid we think human babies are.
They are born very “premature” in comparison to humans, I guess maybe the equivalent to a 4 month fetus? The nervous system develops super early while the rest of the body lags behind; this is necessary because they need to be able to recognize danger, move and find food when they are born because they don’t have parents to do that stuff for them. Their digestive system and cardiovascular system are underdeveloped, weird, and not super functional. They’re hemophagous and have backup yolk gel stuff in their tails which diminish as they grow (you can tell how old a grub is by how big the tail is), and they have blood vessels close to the surface of their skin so they can breathe/supplement the underdeveloped lungs & get nutrients like salts from the environment. Their blood is mixed and the ventricles of their hearts are connected (the hole closes for terrestrial people, but remains open in seadwellers as a valve of sorts that opens while diving). Respiration through skin works better in water than it does in air due to density—and so all trolls begin life as amphibious. It’s only after metamorphosis that they become fully terrestrial. But the system suffering most from underdevelopment is the skeletal system. With the exception of a chondrocranium to protect the brain, they are born with no bones or semblance of a skeletal structure.
And that’s where chitin comes in. In its purest form chitin is leathery; arthropod carapaces are made from chitin plates in the epidermis that are fortified by other minerals to make them hard, but fungi also make use of chitin in their cell walls (in the same way plants use cellulose) and their texture is closer to pure chitin than that of a crab, for example. It doesn’t always form hard plates, and I think it’s possible for chitin to substitute keratin for most of the things we use it for (with a few histological changes). Anyway: hard chitin plates form a grub’s exoskeleton to protect and support the innards and allow movement in absence of an endoskeleton. As they grow, cartilage templates begin to form, but only after pupation does it ossify. During metamorphosis the carapace is lost and chitin is repurposed in the skin, used the same way we use keratin. It’s also what makes up their horns and nails. I’m not sure if chitin could replace keratin for hair, so they may still produce some types of keratin, but the stuff in the epidermal cells is chitin instead.
I don’t think it’s likely that chitin could be used in an endoskeleton. It’s obviously very strong but I’m pretty sure bones made of chitin would be too brittle to sustain the weight of an average person. Our bones are as strong as they are because the extracellular matrix is made up of mineralised collagen I, which is very flexible. Chitin, on the other hand, is a fairly rigid material. Also, like keratin, chitin is constantly flaking off and being replaced; that’s useful for skin on the surface of the body that is constantly being damaged, but doesn’t quite work for a skeleton. (Not to say bone matrixes are static, they certainly aren’t, but the remodeling of bone is a very different process).
LASTLY. Lastly I want to thank you for bothering to reply and for linking realmonstrosities.com because I didn’t know that website existed. And to my followers who don’t give a damn about any of this and hate that I’m making so many huge text posts lately, I’m not sorry one bit and you must have at least skimmed all of this anyway to be reading what I’m saying right now. So I hope it was interesting! Because it sure as hell is to me.