[1] The lettuce slug resembles a nudibranch, but it is not closely related to that clade of gastropods; it is classified as a sacoglossan.

[6] Chloroplasts within their parapodia (fleshy dorsal protrusions) continue to produce energy products through carbon fixation throughout their life and have been found to function efficiently for a little over a month.

[5] Also known as chloroplast symbiosis, kleptoplasty is the energy-providing mechanism that gives the Sacoglossan’s the nickname, “solar-powered sea slugs”, and E. crispata the name, “lettuce sea slug.” As algal food is being digested, the chloroplasts are absorbed into the cells lining the digestive tract and up into their parapodia.

[5][7] Although it hasn’t been exclusively studied for this organism, one possibility of the mechanism behind long-term retention is due to the amount of extracellular components which prolong chloroplast activity, depending on the species of algae eaten.

Typically the egg mass is laid on flat, upright algae, and embryo development takes about 15 days.

[8] Some species of Sacoglossan such as Elysia tuca, invest extra energy to create extra-cellular yolk which is weaved into their egg mass, providing a greater abundance of nutrients for larval growth, which in turn produces larger progeny.