Linruuu - Linru ฅ^•ﻌ•^ฅ

I’ve been thinking about these two specific images nonstop for months

Parasitic crustaceans are wild.

[cw: photos of parasites inside host bodies]

Here is Linguatula serrata, which lives inside the nose of dogs and other Carnivorans. It belongs to group Pentastomida, which has so shed its arthropod appendages that it was long classified as its own independent phylum (attested in fossils all the way from the Cambrian Explosion!), until molecular analyses showed they were in fact strange crustaceans – closest relatives of the relatively normal-looking fish lice (Branchiura).

And then there’s Pennellidae…

Do those horn-things look like crustaceans to you? And yet the family Pennellidae is fully part of Copepoda, the chief component of crustacean plankton. Its body is simply one elongated trunk and a tiny head biting onto the fish, with two long egg cords trailing behind.

Look at the cod worm (Lernaeocera branchialis), another Pennellidae, hanging from the gills of a fish:

It’s those two red things that look like slugs wearing a wig made of soy noodles. Here’s what it looks like on its own, extracted and preserved:

(source) The coiled strings are egg masses. The slug-like part is the copepod’s trunk. The thin branching thing at the bottom is its head, converted into a sort of root system that no longer does head-like things, but rather burrows into the fish host’s blood vessels to feed its eggs. Incidentally, this is just the female; the male still looks like a regular planktonic crustacean.

Now, regular barnacles (Cirripedia) are strange enough…

(source; picture them as shrimps lying on their back, with a digestive system that fell out of the body wall but is still contained by the outer shell, and feathery legs poking out to filter water)

… but parasitic barnacles of clade Rhizocephala go much further:

Here, on the left, is Sacculina carcini. No, not the crab; the yellow sac poking out of the crab’s belly. On the right, its relative Clistosaccus paguri shows what it might look like once extracted.

Sacculina carcini is fun. A larva looks much like any other crustacean planktonic larva, until it finds a suitable host. It stings the unfortunate crab in a vulnerable spot between armor plates, and effectively injects itself into the host, leaving its own shell outside, and transferring only soft tissues.

Once inside, it grows more like a fungus than an animal, turning into a root-like web that infests the crab’s entire body, down to its leg tips. Then it takes over not only the crab’s digestive system, leeching nutrients for its own eggs, but also its nervous system, effectively controlling it like a puppet.

When the parasite is mature, its egg sac starts bulging out of the crab’s body: that’s the yellow part you see in the photo. Male Sacculina stay larvae their whole life: they just mate with the female’s egg sac and then die. The parasite makes the crab take care of itself as if it was the crab’s own eggs. There’s no competition, since the host is sterilized; to leave more food for the parasite, it also stops molting and regenerating lost limbs. If the host is male, and therefore poorly suited to carrying egg sacs under its tail, Sacculina messes with its hormones and effectively turns it female.

Finally the eggs are released and the whole cycle starts again, with the only purpose of making more eggs whose purpose is making more eggs.

(all pictures from Wikipedia unless specified otherwise)

spiny lobster conga line😎

Cute cat who loves shopping in the supermarket. Supermarket rush is in progress.

I can feel…the serotonin and dopamine dropping…i need to make…Crafts

i must make…

b e a d l i z a r d

Why is this so funny to me

one of the best academic paper titles

this cat got hands