WHAT! I’M BACK YES
i heard you guys wanted to learn more about smooshy sea creatures so i have returned from my hibernation to sate your desires. YES YES
okay, elysia chlorotica. what’s the haps? it’s a solar-powered sea slug, no big deal…!
when elysia chlorotica (commonly eastern emerald elysia) is a juvenile, it’s reddish brown. only after it begins eating algae does it turn green. at first, it needs to regularly ingest algae to retain the chloroplasts, but over time they become established and the elysia can start to photosynthesize directly. in one experiment, elysia were denied algae and were able to live off the energy produced by their plastids for nearly a year! this is a much stable form of kleptoplasty than found elsewhere in the invertebrate kingdom;various dinoflagellates, ciliates, foraminifera, etc, sequester plastids
basically, elysia eats algae, but does not fully digest the chloroplasts. it retains them in branches of its body-wide digestion gland, and it produces algal genes necessary for plastid function. suggestions on how this happened include lateral gene transfer or a virus that affected both algae and slug. evolutionary reward for this acquisition is obvious! it can live for months with no external food source.
to quote the encyclopedia of life, “this sea slug is unique among animals to possess photosynthesis-specific genes and is an extraordinary example of symbiosis between an alga and mollusc as well as a genetic chimera of these two organisms.”
how succinct! and bonus points for use of the word ‘chimera’.