Database of marine protists from Disko Bay, West Greenland
  Chaetoceros socialis

Class: Bacillariophyceae

Genus: Chaetoceros

Species: socialis

Author: Lauder 1864

Description: : Cells united into short to medium-length chains that form spherical colonies. Valve face is flat to slightly concave with a small inflation, cell corners diagonally cut. Setae thin. Intercalary setae originate inside the valve margin and cross over at or outside the chain edge. Basal parts short to medium-length. Three setae of each cell are directed towards one side of the chain while one, elongated seta is directed towards the opposite side. The spherical colony is formed by intertwining of the long setae from numerous cells. Resting spore valves are unevenly undulated. Chaetoceros socialis f. socialis possesses smooth resting spores while in C. socialis f. radians the resting spores are spiny (Ostenfeld 1910).

Previous records: A widespread species, which may be very important close to the sea ice in polar regions (Gran 1902, von Quillfeldt 1996, Booth et al. 2002) and in the spring and autumn bloom in temperate regions (Sundström 1973, Rines & Hargraves 1988, Jensen & Moestrup 1998, Bérard-Therriault et al. 1999). Grřntved & Seidenfaden (1938) reported it as blooming in June-July soon after melting of the snow. Resting spores are frequently reported from the sea ice (von Quillfeldt 1996).

Reference(s): Cupp 1943
Hasle & Syvertsen 1996
Lauder 1864
Rines & Hargraves 1988
Jensen & Moestrup 1998