Elysia atroviridis

• Comment: Notable per https://www.scientificamerican.com/article/this-sea-slug-can-chop-off-its-head-and-grow-an-entire-new-body-twice1/ and sufficiently sourced (for a stub), thank you Ozzie10aaaa (talk) 13:15, 25 January 2024 (UTC)

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Elysia atroviridis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Family:	Plakobranchidae
Genus:	Elysia
Species:	E. Atroviridis
Binomial name
Elysia Atroviridis

Elysia atroviridis is a benthic species of sea slug belonging to the family Plakobranchidae (also know as Elysiidae) native to the northwest pacific. E. atroviridis slugs live up to three meters deep, and are generally dark green in skin colour with small, black spots all around the body. E. atroviridis is a member of the superorder Sacoglossa, and thus possesses the ability to perform Kleptoplasty. E. atroviridis and Elysia marginata are notable for possessing the ability to completely autotomize their bodies and grow them back within 20 days.

Kleptoplasty

Being a member of the superorder Sacoglossa, E. atroviridis is capable of kleptoplasty, which is the process of taking chloroplasts from plants and using them for photosynthesis. Kleptoplasty is performed when the slug eats algae and partially digests it, but keeps the chloroplasts intact, incorporating them into their digestive tract's tissues, which allows the chloroplasts to stay alive and contribute energy to the host via photosynthesis.

Autotomy

E. atroviridis, along with E. marginata possessthe ability to completely autotomize their bodies, and survive without their heart, kidneys, reproductive organs, etc. The method they use is unknown, but it is theorized the groove on their neck which is at the location where the head detaches plays a role in the autotomy, and the aforementioned kleptoplasty plays a role in keeping the slugs alive without the digestive system, but aside from that, it is unknown how they manage to stay alive without their major organs. The bodies never regrew the head, and responded to tactile stimuli, but eventually stopped and grew pale, presumably from losing chloroplasts.

Function

The function of the autotomy is unknown. 82 E. atroviridis specimens were infected with a parasitic copepod, and three autotomized. The researchers suggested that the slugs autotomize as a reaction to the infection. Furthermore, all slugs who autotomized were infected with a parasite, and all regrew their bodies back with no parasite. The autotomy could not be a response to predataion, because it takes several hours to autotomize, and researchers attempted to simulate a predator attack but no autotomy was attempted in the slug.