Cunningham, 1892
Description
Anterior nectophore [Muggiaea atlantica ]: small, with five complete but relatively straight longitudinal ridges. The hydroecium is deep and extends to about one third of the height of the nectophore. The long, thin somatocyst reaches the apex of the nectosac.
Eudoxid: the bract is roughly conical, with a flattened facet, an asymmetrical basal process, and a shallow hydroecial depression. The phyllocyst is club- shaped. The gonophore has four longitudinal ridges which spiral to the right. There is a short, curved mouth plate.
Size
Anterior nectophore up to 7 mm in height.
Depth range
Common in shallower waters.
Remarks
The eudoxid stage of Muggiaea atlantica is indistinguishable from that of the related species Muggiaea kochi (Will, 1844). The hydroecium is deeper than in Muggiaea kochi. Both Muggiaea species are of similar size and have an overlapping distribution. Muggiaea atlantica is supposed to be an indicator of the incursion of warmer waters on to the Continental Shelf, although peaks of abundance have been noted at all times of the year. An alternation in the occurrence of this species and Muggiaea kochi was observed in the English Channel.
Distribution in the North Sea
Muggiaea atlantica has been recorded from the northern North Sea.
World distribution
Shallower waters of the Atlantic Ocean and the Mediterranean Sea. The species is supposed to be an indicator of the incursion of warmer waters on to the Continental Shelf, although peaks of abundance have been noted at all times of the year. An alternation in the occurrence of this species and the related Muggiaea kochi was observed in the English Channel.
[After Kirkpatrick and Pugh, 1984]
Remark
In July 1989 a population of Muggiaea atlantica invaded the German Bight, reaching abundances of up to 500 colonies per m^3, having great impact on the ecosystem (Greve, 1994). Not only this species, but also the pelagic tunicate Doliolum nationalis invaded the German Bight in 1989, after a relative warm summer; the flourishing of these species west off the British Isles and the subsequent seeding into the North Sea is thought to be related with summer temperatures that are higher than normal (Lindley et al., 1990).