(Brandt, 1834)
Description
Adult medusa with thick central disc, plano-convex lens-shaped, margin thin. Stomach about half as wide as disc. Radial canals 60-100, occasionally up to 150; gonads extending along almost their whole length.
Marginal tentacles 10-30 (rarely, up to 40); with 6-8 times as many small bulbs [A.macodactyla-tentbase ]. Tentacle bulbs broad, each with a distinct abaxial keel and a prominent excretory papilla; statocysts very numerous. [After Kramp, 1961, and Russell, 1970b].
Size
Medusa umbrella up to ca 75 mm wide.
Ecology
Reproductive Season not known. Fission of apparently fully grown medusae into two viable offspring was recorded June-August off Baja California, Mexico (Stretch and King, 1980).
Depth range
Coastal.
Distribution around the British Isles
Recorded only from Valencia (SW Ireland) and Plymouth (Russell, 1953a, as A. pensilis ), but likely to occur occasionally in SW of area.
Distribution in the North Sea
Probably not reaching the North Sea.
World distribution
Near-cosmopolitan in warmer coastal waters; in the North Atlantic Ocean, thought usually to stop just south of the present faunal area.
Remark
Russell, 1953a gave a wealth of detail concerning the relative and absolute sizes of various organs at different bell diameters though his account unfortunately confused the present species with A. pensilis.
[After Cornelius, 1995a]