Elysia crispata, common name

Common name

A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...

 the lettuce sea slug, is a large and colorful species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of sea slug

Sea slug

Sea slug is a common name used for several different groups of saltwater snails that either lack a shell or have only an internal shell, in other words this name is used for various lineages of marine gastropod mollusks that are either not conchiferous or appear not to be.The phrase "sea slug" is...

, a marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 gastropod mollusk.

The lettuce slug resembles a nudibranch

Nudibranch

A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...

, but it is not closely related to that order of gastropods. It is instead a sacoglossa

Sacoglossa

Sacoglossa, commonly known as the sacoglossans or the "sap-sucking sea slugs", are a clade of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia...

n.

Distribution

This species lives in the tropical parts of the western Atlantic, the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

 faunal zone.

Description

This species is called the lettuce slug because it is often green in color, and it always has a very frilly edge to its parapodia. This makes the slug resemble the curly kinds of lettuce

Lettuce

Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...

, such as the lollo rosso variety. The maximum length of this species is about 50 mm.

The lettuce slug is extremely variable in color: it can also be blue, or very pale with red lines or yellow lines.

Anatomy

This sea slug (in common with some other sacoglossans) has algal chloroplast

Chloroplast

Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...

s (from its seaweed food sources) functioning within its tissues, providing it with sugars. This unusual phenomenon is known as kleptoplasty

Kleptoplasty

Kleptoplasty or kleptoplastidy is a symbiotic phenomenon whereby plastids from algae are sequestered by host organisms. The alga is eaten normally and partially digested, leaving the plastid intact. The plastids are maintained within the host, temporarily retaining functional photosynthesis for use...

.