Clava multicornis ( Forsskål, 1775 )

Calder, Dale R., 2012, On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region 3171, Zootaxa 3171 (1), pp. 1-77 : 10

Clava multicornis ( Forsskål, 1775)

Fig. 6

Hydra multicornis Forsskål, 1775: 131 .

Clava sqvamata .— Segerstedt, 1889: 6 [incorrect subsequent spelling].

Clava squamata .— Segerstedt, 1889: 23.— Lönnberg, 1898: 51.— Jäderholm, 1909: 44, pl. 1, figs. 11, 12.— Gislén, 1930: 320.— Kramp, 1935b: 65.— Jägerskiöld, 1971: 61.

Clava glomerata Lönnberg, 1899a: 45 , unnumbered fig.; 1899b: 17.

Type locality. “ In freto Öresund…” ( Forsskål 1775: 131).

Museum material. Tjärnö, floating dock at Sven Lovén Centre for Marine Sciences , 58°52’33.68”N, 11°08’43.65”E, <1 m, 07.ix.2010, collected manually, on floating Ascophyllum nodosum , one colony, with gonophores, ROMIZ B3892 .— Saltö naturreservat, outer ledge, 58°52’40”N, 11°06’53”E, <1 m, 11.ix.2010, collected manually, on attached Ascophyllum nodosum , one colony, with gonophores, ROMIZ B3926 .

Remarks. Colonies of Clava multicornis ( Forsskål, 1775) were promptly found in the study area on fucoid algae at and just below the surface of the water. The species is also known to occur intertidally, avoiding desiccation by clumping into a jelly-like mass ( Edwards & Harvey 1975). When present on fucoids, colonies are often found in axils of its algal substrate, and abundances are reportedly greater in wave-sheltered than in wave-exposed areas ( Rossi et al. 2000). The biology of this shallow-water hydroid has recently been reviewed by Schuchert (2008a). Earlier, Edwards & Harvey (1975) presented evidence from laboratory and field experiments that a diffuse colony form sometimes identified as Clava squamata ( Müller, 1776) is conspecific. So too are C. leptostyla L. Agassiz, 1862 from the western North Atlantic and C. glomerata Lönnberg, 1899 from the Swedish west coast ( Edwards & Harvey 1975). Other synonyms are listed in Schuchert (2008a).

Clava multicornis is well-known in southwestern Scandinavia ( Jäderholm 1909; Kramp 1935b), although its occurrence in the Oslofjord has been found to vary considerably from year to year ( Christiansen 1972). Colonies become dormant in the region during winter, but new hydranths are regenerated from stolons in spring ( Kramp 1935b).

Reported distribution. West coast of Sweden.—Bohuslän to Öresund ( Jäderholm 1909: 44, as C. squamata ).

Elsewhere.—Boreal waters of the North Atlantic: from the Barents and White seas to Portugal in Europe ( Naumov 1960; Schuchert 2008a), and from southern Labrador to Long Island, New York, in North America ( Fraser 1944, as Clava leptostyla ).