(Péron and Lesueur, 1809)
Description
Umbrella with considerable conical, solid, apical projection, jelly of uniform thickness around top [Amphinema dinema ]. With four undivided radial canals, interradial centripetal canals absent. Gastric peduncle absent, manubrium with broad base, sessile [A.dinema-medusa ]. Manubrium cross-like in section, flask-shaped, almost as long as bell cavity. Mouth with four prominent, recurved lips. With eight simple adradial gonads, smooth, on manubrium wall only. Two perradial, hollow, marginal tentacles with large elongated conical basal bulbs; bulbs without ocelli. With 14-24 small marginal warts.
Young: A.digitale-young-habitus and young female: A.dinema-young female-habitus .
Size
Umbrella up to 4 mm wide and 6 mm high.
Colour
[A.dinema-female-habitus ] Marginal tentacle bulbs bright violet; manubrium emerald green, in mature females with an ochreish tinge; marginal tentacles with yellow-ochre core; a small mass of ochreish pigment in each of two perradial marginal warts and at times on other marginal warts.
Ecology and depth range
Meropelagic; neritic. In south-western British waters medusae appear in the plankton in late summer, peak abundance in September and October.
Distribution in the North Sea
Southern North Sea, English Channel.
World distribution
North Atlantic Ocean including Mediterranean Sea; E and W South Atlantic and Indo-Pacific Oceans.
[After Russell, 1953a; Russell, 1955; Kramp, 1959; Bouillon, 1999]