(Van Beneden, 1844)
Description
Umbrella nearly spherical [Ectopleura dumortieri ], jelly very thick, especially in apical region, though not projecting; apical canal sometimes present. Length bell cavity about 2/3 height of umbrella. Velum fairly broad. Exumbrella with four pairs of nematocyst tracks. Four radial canals and ring canal narrow. Manubrium very large, spherical at base, tapering towards mouth; extensile, stretching beyond umbrella margin when fully extended. Mouth circular, simple, armed with nematocysts. Gonads completely surrounding manubrium, leaving mouth free. Four perradial marginal tentacles with nematocysts in abaxial clusters [E.dumortieri-expanded ]. No ocelli on the large marginal tentacle bulbs.
Size
Umbrella up to 2-3 mm high.
Colour
[E.dumortieri-habitus ] Marginal tentacle bulbs brownish or yellow flecked with red; mouth orange or crimson; manubrium with band of fine red spots round centre, and brownish or yellow circle of pigment round base near junctions with radial canals.
Ecology and depth range
Neritic. Recorded singly or in small numbers, in south-western British waters from March to December. In the laboratory hydroids have been found to produce medusa in April and September.
Distribution in the North Sea
Southern North Sea, Skagerrak and W English Channel.
World distribution
North Atlantic Ocean, including Mediterranean Sea; South Atlantic and Indo-Pacific Oceans.
[After Russell, 1939; Russell, 1953a; Bouillon, 1999]