Laomedea flexuosa Alder 1857

Laomedea flexuosa Alder, 1857

Fig. 50

Laomedea flexuosa Alder, 1857: 122.— Östman, 1979a: 6; 1982a: 156; 1982b: 228; 1983: 6; 1999: 19 [the specific name flexuosa Alder, 1857 conserved and placed on Official List of Specific Names in Zoology, Opinion 1345 (ICZN 1985)].

Campanularia flexuosa.— Segerstedt, 1889: 14, 25.— Jäderholm, 1909: 68, pl. 6, fig. 15.

Campanularia (Laomedea) flexuosa.— Gislén, 1930: 316.

FIGURE 51. Obelia dichotoma: part of colony with two hydrothecae, ROMIZ B3898. Scale equals 0.5 mm.

Type locality. British Isles (Cornelius & Garfath 1980: 284).

Museum material. Saltö naturreservat, outer ledge, 58°52’40”N, 11°06’53”E, <1 m, 11.ix.2010, collected manually, on Ascophyllum nodosum, two colonies, up to 1.5 cm high, with female gonothecae, ROMIZ B3922.

Remarks. Together with Dynamena pumila (Linnaeus, 1758) and Clava multicornis (Forsskål, 1775), Laomedea flexuosa Alder, 1857 is common on boreal shores of both western Europe and eastern North America. While frequent intertidally on fucoids and other substrates, the species has occasionally been recorded as deep as 100 m (Cornelius 1995b). Records of L. flexuosa in western Sweden have predominantly been from very shallow waters, and it was not recorded at all in the extensive collections of Jägerskiöld (1971), most of which were obtained in deeper waters by dredging. In the nearby Oslofjord, southern Norway, it is common from the intertidal zone to a depth of about 3 m on algae and stones (Christiansen 1972). In Danish waters it is abundant where suitable substrates exist, and penetrates deep into the Baltic Sea (Kramp 1935b). The restricted vertical distribution of this hydroid in the White Sea was attributed by Marfenin & Belorustseva (2008) to intensive release of planula larvae during low tide, and to their subsequent rapid settlement as the water began to rise.

Notes on the biology of this species are given by Cornelius (1982, 1995b), and its cnidome has been characterized by Östman (1979a, 1982b, 1983, 1999). Laomedea flexuosa is the type species of the genus Laomedea Lamouroux, 1812, so designated under the plenary powers by the ICZN (1985) in Opinion 1345.

Reported distribution. West coast of Sweden.—Koster to Öresund (Segerstedt 1889).

Elsewhere.—In the North Atlantic from Svalbard and the north coast of the Russian Federation to the Mediterranean Sea, and southwards to west Africa in the east (Linko 1911, as Campanularia flexuosa; Cornelius 1982; Voronkov et al. 2010), and from the Gulf of St. Lawrence to Long Island Sound in the west (Fraser 1944, as Campanularia flexuosa). It has been reported as an invasive species in the Sea of Japan (e.g. Kashin et al. 2003). A record of this boreal hydroid from the Tortugas, Florida (Wallace 1909: 137, as Campanularia flexuosa), questioned by both Fraser (1944) and Vervoort (1968), is certainly based on a misidentification.