Molgula bouvetensis Michaelsen 1904

• Main Authors: Monniot, Françoise, Dettai, Agnès
• Format: Other/Unknown Material
• Language: unknown
• Published: 2015
• Subjects: Biodiversity; Taxonomy; Animalia; Chordata; Ascidiacea; Pleurogona; Molgulidae; Molgula; Molgula bouvetensis; Antarctic; Bouvet; Bouvet Island; Antarc*
• Online Access: https://zenodo.org/record/6097440; https://doi.org/10.5281/zenodo.6097440

Molgula bouvetensis (Michaelsen, 1904) Bouvet Island, BIOMASS survey MD 24. 18 /08/ 1980, 54° 22 ’ S – 03° 15 ’ E, 150–218 m; 19 /08/ 1980, 54° 21 ’ S – 03° 24 ’ E, 192–218 m; 20 /08/ 1980, 54° 28 ’ S – 03° 21 ’ E, 195–203 m; 20 /08/ 1980, 54° 27 ’ S – 03° 23 ’ E, 150–165 m; 21 /08/ 1980, 54° 25 ’S – 03°09’ E, 219– 305m. Numerous specimens of very similar shape were collected by trawl. They are not very well fixed but in good enough condition to be compared with the 3 other groups of Antarctic Molgula with peduncle. Their general anatomy can hardly isolate them at first sight, only small differences can be pointed out but they may be sufficient to isolate and support the distinct species inhabiting a distant region. The description of Michaelsen (1904) is very detailed and corresponds to our observations. The specimens have an ovoid body 4 to 8 cm high, narrowing in a soft peduncle of variable size but not exceeding the body length. The peduncle ends in a tuft of filaments (Fig. 15 B). The atrial siphon is apical, the oral siphon at 1 / 3 of the dorsal side. The tunic is thin, very resistant, granular at the surface and smooth on the internal side. It is often densely covered with various epibionts. The musculature of the body wall has the same bundles as in other Molgula groups, except a small difference in the middle of the body sides: the muscular ribbons are interrupted above the gonads only, but not over the kidney and the gut (Fig. 16 B). There are 8 oral tentacles of irregular length, less bushy than in other groups (Fig. 16 A). The dorsal tubercle has horns interiorly curved but not rolled; it opens on the left. The dorsal lamina is a high membrane with a smooth edge, prolonged on the left side of the oesophagus to join the base of the branchial folds where it forms large undulations. The branchial sac does not significantly differ from other close species. It has 7 high folds folded over the dorsal side (Fig. 15 A). The distribution of the longitudinal vessels is the common one, for example on a part of ...