''Elysia viridis'' is a sacoglossan sea slug of the family Plakobranchidae. They are occasionally nicknamed the sap sucking slugs for their ability to suck the cytoplasm out of the algae they prey upon,. Adult length is considered to be between 15–20 mm long, and they vary in color from greens to brownish hues. ''Elysia viridis'' is one of few organisms capable of

kleptoplasty Kleptoplasty or kleptoplastidy is a process in symbiosis, symbiotic relationships whereby plastids, notably chloroplasts from algae, are sequestered by the host. The word is derived from ''Kleptes'' (κλέπτης) which is Greek language, Greek ...

; when consuming the

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

of its algal prey ''E. viridis'' can retain the

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

s in working condition, and being able to benefit from their continued

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

Description

Adult length of ''E. viridis'' ranges between 15-20mm, with an healthy adult weight of 15–20 mg. The surface of the slug is covered in tiny spots of red, yellow, blue or green that are reported to have a glistening appearance.

Parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; : parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed late ...

extend from the sides of the slug, and are the main location of captured

s. Rhinophores extend upward from its head. ''Elysia viridis'' feed using radular teeth, which in this species, '' E. gordanae,'' can vary in design based upon the diet of the individual.

Distribution

''Elysia viridis'' is located in the Northeastern Atlantic, primarily around the

British Islands The British Islands is a term within the law of the United Kingdom which refers collectively to the following four polities: * the United Kingdom of Great Britain and Northern Ireland; * the Bailiwick of Guernsey (including the jurisdictio ...

, but has been found further north in

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

and

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

, as well as in the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

. A report of ''E. viridis'' being found in south Africa was published in 1987, but the identification that specimen was later changed to ''Elysia sp.'' by the same author. ''Elysia viridis'' occurs in the

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

typically submerged on its algal prey between 1 and 5 meters below the surface.

Ecology

''Elysia viridis'' feed on algae, primarily of the genus ''Codium,'' with a noted favorability towards ''C. fragile, C. sericea,'' and ''C. rupestris''''. E. viridis'' has been found to be less selective of algal hosts than other members of ''Elysia''. ''E. viridis'' deposit coiled egg masses onto the thallus of its prey, or on nearby underwater surfaces, that hatch into a larval stage called a

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod taxono ...

. Veliger are planktotrophic and consume free floating unicellular algae. Once the

propodeum Propodeum labelled within the alitrunk of an ant worker The propodeum is a term that can refer to unrelated structures in insects or in mollusks. Insects The first abdominal segment in Apocrita Hymenoptera (wasps, bees and ants) is known a ...

develops on the larvae they search for a macroalgal host, contact with which appears to trigger a metamorphosis into the adult form, but the trigger for this metamorphosis is unconfirmed.

Kleptoplasty

''Elysia viridis'' is most notable for its capability of performing

, and maintaining a subcellular endosymbiotic relationship with

s derived from the algae in the genus ''

Codium ''Codium'' is a genus of edible green macroalgae (or seaweed) under the order Bryopsidales. The genus name is derived from a Greek word that pertains to the soft texture of its thallus. One of the foremost experts on ''Codium'' taxonomy was P ...

,'' most often '' C. fragile''. When consuming the

of the algae, ''E. viridis'' is able to retain the

s in a functional state; chloroplasts are phagocytized, while digesting the other cytoplasmic contents are digested. The captured chloroplasts (kleptoplasts) retain their ability to photosynthesize, the photosynthates of which can benefit the slug nutritionally. Kleptoplasts can also be broken down and used as a pre-stored energy source in situations where the slug is deprived of food sources and light.

References

External links