Dujardin, 1843
Description
Umbrella bell-shaped, slightly higher than wide [Cladonema radiatum ]; jelly moderately thin, sometimes a slight apical projection present; velum very broad. Usually eight, sometimes ten, radial canals corresponding with an equal number of marginal tentacles.
Manubrium spindle-shaped [C.radiatum-medusa ], not extending beyond umbrella margin, its middle region usually with five, sometimes four, perradial pouches; mouth with a similar number of short lips armed with nematocyst clusters.
Gonads completely surrounding apical 2/3 of manubrium. Marginal tentacles branched, branches beset with numerous nematocyst clusters [C.radiatum-adult ]; tentacular bases elongate and thickened; one to four, usually three, organs of adhesion on each tentacular base. Tentacular bulbs each with an abaxial ocellus.
Young stages: C.radiatum-newly, C.radiatum-young subumbrellar.
Size
Umbrella up to 4 mm high.
Colour
Manubrium and marginal tentacles red, bright red or brown; ocelli black or deep crimson.
Ecology and depth range
This medusa can creep or swim [C.radiatum-creeping ]. Seasonal occurrence is little known.
Distribution in the North Sea
Throughout the North Sea.
World distribution
N Atlantic Ocean including Mediterranean Sea and Black Sea; NW Pacific Ocean.
[After Russell, 1953a; Russell, 1977a; Kramp, 1959]