Do you have any fun facts/headcanons about DSB?
Or any thoughts you have about their anatomy!
BOY DO I EVER lmao- I did a TON of research on Jorunna parva and other nudibranchs for this fic. And I will gladly share my sources at the end, if anyone else is interested.
First, a brief rundown on Sea Bunny Anatomy:
The cute little "ears" we love are actually rhinophores, a chemosensory structure- or a scent organ. You can read more about them here.
The "mouth" (as mentioned by Ramirez in the fic) is actually a set of oral tentacles or sensory organs "that help determine whether something is safe to eat.” When a sea slug wants to eat they extend their feeding apparatus, which has a radula on the end. The radula is like a large, toothy tongue comprised of chitinous ribbons that shred food. So watching a Sea Bunny eat would be absolutely disgusting.
The "fur" covering their bodies are papillae- more specifically Caryophyllidia. I may have incorrectly described these as cerata in the fic somewhere- which, on some species of nudibranchs, are venomous! (Cerata seem to only be present in aeolid nudibranchs, not dorid species like Jorunna parva. Note for future Owl.) These serve as an additional sensory organ...which for the life of me I could not find any specific details on what that means. It makes sense though, because sea slugs can't see shit. They have to rely on their other senses to navigate the world around them. Nudibranch eyes are very small and difficult to see.
The feet of a mollusk/sea slug are... well, a singular foot. Used for movement. I headcanon that, like their terrestrial relatives, they are sticky and can scale vertical surfaces. Little terrors.
Last but not least, the fluffy tail is also misleading: this structure is actually their gills! This is where the species gets their name. Nudibranch translates to 'naked gills.' On a live Jorunna parva, it does look like a little cotton tail.
Sharks (and Sebastian) have gill slits that connect to the pharynx to draw oxygen from the water, whereas nudibranchs like Sea Bunnies and Axolotls "pull water through their mucous membranes. The capillaries then extract the oxygen and deliver it to the body." (Source)
If you are looking for more information I would HIGHLY recommend visiting https://seaslugforum.net/. I had this site open for most of the early Sea Bunny Chapters. They have information on reproduction (which could be a WHOLE separate post), their life cycle, and information on hundreds of different species of sea slugs- not JUST nudibranchs! It's a perfect resource if you want to give your OC any fun traits.
Also I'm ngl Wikipedia truly came in clutch for me.
I hope that is what you were looking for OP- thank you for coming to my DSB science lecture. If I have any details wrong please let me know- I don't actually have a science background despite what you might believe from the copious amounts of fish science in my series.