Symsagittifera roscoffensis, formerly called Convoluta roscoffensis, is a free-living acoelomorph worm

Acoelomorpha

The Acoelomorpha are a disputed phylum of animals with planula-like features that were considered to belong to the phylum Platyhelminthes. In 2004 molecular studies demonstrated that they are a separate phylum, although their position in the tree of life is contentious; most researchers believe...

.

Appearance

Symsagittifera roscoffensis is a small (about 15 mm long) flat worm. Due to the algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, Tetraselmis

Tetraselmis

Tetraselmis is a genus of phytoplankton. Tetraselmis has a very high lipid level; their amino acids stimulate feeding in marine organisms . Tetraselmis is green, motile, and usually grows 10 µm long x 14 µm wide.The species T...

 convolutae, which it assimilates into its body cavity, it has green colour. Its common name in the Channel Islands is "mint sauce worm" by reason of its appearance.

Ecology and distribution

In its adult stage, the worm lives off the excesses of its symbiotic algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, although the mouth is still present posteriorly to the statocyst

Statocyst

The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, echinoderms, cephalopods, and crustaceans. A similar structure is also found in Xenoturbella. The statocyst consists of a sac-like structure containing a mineralised mass and numerous...

. The worm provides shelter and some nutritional benefits in return.

The worm can be found in shallow water on sheltered sand beach

Beach

A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...

es along most of the Atlantic Coast (including the coasts of Wales, Brittany, the North of Spain and Portugal).

Name

The genus name was originally spelled Simsagittifera; Mamkaev & Kostenko corrected it in 1991 to Symsagittifera but Faubel et al. (2004) maintain that Simsagittifera should be retained.

Significance to humans

Symsagittifera roscoffensis is one of the model organism

Model organism

A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...

s for studying the development of bilateria

Bilateria

The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back...

ns.

External links

• http://www.rzuser.uni-heidelberg.de/~bu6/Convoluta.html
• http://animaldiversity.ummz.umich.edu/site/resources/Grzimek_inverts/Acoela/Convoluta_roscoffensis.jpg/view.html
• http://www.konig-photo.com/english/galerie/zoom.asp?pre=8169&NumPhoto=8170&suiv=8171&Rub=476
• http://www.paulchambers.eu/jersey_marine/comb_jellies.html