(Steenstrup, 1850)
Description
Umbrella globular, sometimes wider than high [Bougainvillia principis ]; jelly moderately thick; velum fairly broad. Four radial canals broad and ring canal narrow.
A slight broad-based gastric peduncle often present, manubrium short, with broad base, in section cross-shaped. Mouth with four oral tentacles inserted above mouth opening, dichotomously branched 5-6 times terminating in small nematocyst clusters, basal trunk of oral tentacle short [B.principis-tentacles ].
Gonads situated adradially on manubrium, swollen.
Four large marginal tentacular bulbs each with a group of 20-30 tentacles of one kind in a single row. With round, black ocelli [B.principis-tentacles ].
Young medusa with abundant nematocysts and four moderately deep interradial and four less deep perradial longitudinal furrows on exumbrella.
Development: B.principis-stages.
Size
Umbrella 7-11 mm high.
Colour
Manubrium wine-red or golden yellow; marginal bulbs wine red, dark reddish brown, brown or orange, with central mass of dark pigment with rays radiating towards the tentacles [B.principis-female-habitus ].
Ecology
A northern boreal species usually appearing earlier in southern British waters than in the far north; generally present in May.
Distribution in the North Sea
Northern and southern North Sea.
World distribution
NE North Atlantic Ocean; Arctic Ocean.
[After Russell, 1953a; Kramp, 1959]