Lettuce Sea Slug

Identification overview

The lettuce sea slug is an animal whose folded body edges resemble a small leafy head of lettuce. Elysia crispata has broad, ruffled lateral flaps called parapodia. Green is a familiar color, but pale, blue or yellow details can alter its appearance. Look at the body shape and folded edges rather than expecting every individual to have identical colors.

This is a sea slug, not a piece of drifting algae. Photograph the head and the complete ruffled outline when possible. A close-up of one green fold can hide useful identification features. Observe the animal where it is crawling instead of lifting it onto a cleaner background.

A documented Key Largo reef resident

A peer-reviewed study published in 2026 explicitly describes collecting living Elysia crispata by scuba at Pickles Reef off Key Largo, at roughly five meters depth. This is direct local evidence, not an inference from the broad phrase “Florida Keys.” A University of Bergen field photograph also identifies an animal from Key Largo. Neither source promises a sighting on any particular trip or establishes occurrence throughout the entire Vero–Key Largo corridor.

The 2026 study discusses reef-associated and sheltered nearshore forms. Older references sometimes called the nearshore form Elysia clarki; current synonym treatment places that name under Elysia crispata. These names should lead to one species profile, not be counted as two new additions. Habitat and appearance can vary within the species.

Food and borrowed solar machinery

The slug feeds on green macroalgae and retains chloroplasts, the cellular structures that carry out photosynthesis. Retained chloroplasts remain functional within the slug’s digestive tissues. This process, called kleptoplasty, gives “solar-powered sea slug” a basis in biology, but does not turn the animal into a plant or justify assuming it can live indefinitely on light alone.

Reproduction and responsible watching

The species is hermaphroditic, with both male and female reproductive functions, and reproduction includes cross-fertilization and egg development. The reviewed modern study describes limited dispersal associated with a short, nonfeeding early developmental stage. It does not establish a local spawning season for visiting divers.

Its ruffled body, retained chloroplasts and changing scientific-name history provide three good reasons to look closely. Keep fins clear of the bottom and do not handle the slug to expose its underside. Treat this page as an identification guide, not permission to collect aquarium animals. Consult current FWC marine-life rules and the regulations for the precise sanctuary, park or access point before considering removal.

References

• 2026 genome study with Pickles Reef collection methods
• University of Bergen Key Largo field photograph
• Animal Diversity Web identification and reproduction
• GBIF synonym treatment
• FWC marine-life rules

Current Florida collection cautions

Reviewed November 12, 2026. FWC regulates sea slugs as marine life. Licensing, gear, live-condition requirements, limits and site closures apply. Confirm the exact park or sanctuary rules before collection. Observe without removal; an occurrence record does not authorize harvest. Official FWC marine-life collection rules

Make your next dive happen

Review current dates, availability, prices, inclusions and requirements on each listing before booking or buying.