Symsagittifera roscoffensis

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Symsagittifera roscoffensis
Numerous specimens of Symsagittifera roscoffensis

Numerous specimens of Symsagittifera roscoffensis

Systematics
Trunk : Xenacoelomorpha
Sub-stem : Acoelomorpha
Order : Acoela
Family : Convolutidae
Genre : Symsagittifera
Type : Symsagittifera roscoffensis
Scientific name
Symsagittifera roscoffensis
( Graff , 1891)

Symsagittifera roscoffensis is a flatworm-like organism thatlivesin close symbiosis with a photosynthetically active species of algae ( Tetraselmis convolutae ).

description

Symsagittifera roscoffensis , original drawing by Ludwig von Graff

The individuals of Symsagittifera roscoffensis are egg-shaped and up to 15 mm long. The ingestion of numerous unicellular green algae gives them their characteristic green color.

distribution and habitat

The species occurs on the channel coasts of southern England and northern France as well as on the Atlantic coast of Brittany. (The specific epithet " roscoffensis " refers to the French town of Roscoff in Brittany.)

It lives in shallow, sandy, sheltered bays. It can be so common, especially in tidal pools, that it turns the water green.

nutrition

Juvenile individuals ingest the symbiotic algae without digesting them. The transition to the adult stage is associated with drastic anatomical changes: the mouth opening and esophagus are receded, while the algae spread through the tissues of the entire worm body. Up to 25,000 individual algae could be detected in a single Symsagittifera roscoffensis individual. Adult individuals are completely dependent on the algae diet. These supply them with carbohydrates and oxygen, in return the algae receive nitrogen compounds. Symsagittifera roscoffensis is therefore a fine example of a mutualistic symbiosis . Proponents of the endosymbiotic theory cite the case as a possible developmental step towards a real endosymbiosis.

Symsagittifera roscoffensis in a tide pool .
Symsagittifera roscoffensis , the 'Roscoff worm'

swell

  1. ^ PM Holligan & GW Gooday: Symbiosis in Convoluta roscoffensis . In: Symposia of the Society of Experimental Biology 29 (1975), pp. 205-227.
  2. ^ AE Douglas: Establishment of the symbiosis in Convoluta roscoffensis . In: Journal of the marine Biological association 63 (1983), pp. 409-418.

Web links

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