Abstract
The invasive ctenophore Mnemiopsis leidyi has been detected during late summer and autumn 2006 in northern Europe. So far it has been found in the southern North Sea area, along the Swedish west coast, in the southwestern Baltic and along the south and southwestern Norwegian coasts. From the large populations observed, it is obvious that it must have been introduced before 2006, but remained unrecorded until this autumn.
Highlights
The only comb jelly known to be widespread in the Baltic is the ”Sea Gooseberry” Pleurobrachia pileus
B. cucumis has a branched gastrovascular system between each of the 8 longitudinal rows of comb plates, while no trace of such a system is seen in B. gracilis
I had myself observed a few specimens from a plankton haul in the vicinity of the Tjärnö Marine Biological Laboratory (TMBL) at the northern part of the
Summary
The only comb jelly known to be widespread in the Baltic is the ”Sea Gooseberry” Pleurobrachia pileus This species, which may reach a length of 25 mm except its tentacles, is common in the marine waters of almost all northern Europe and can tolerate salinities down to ca 6.5 psu. A second and smaller (usually less than 3 cm long) species of the latter genus, B. gracilis Künne, 1939, is common in the North Sea and the Skagerrak (and likely in the Kattegatt) and may possibly enter the southwestern part of the Baltic occasionally.
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