On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region

Abstract

An account is given of 48 species identified in a small collection of hydroids from the west coast of Sweden. Assigned to 39 genera and 18 families, most are well-known from boreal waters of the North Atlantic Ocean. Campanulina panicula G.O. Sars, 1874 is referred to Racemoramus, a new genus of leptothecates distinguished in part by having monopodial growth, rigid and non-segmented hydrocauli, and grape-like clusters of hydrothecae that arise at irregular intervals from the stem. The name Sertularia dumosa (now Lafoea dumosa) is taken to have been made available by Fleming (1820), not Fleming (1828). As such, it is not threatened by a virtually unused subjective synonym (Lafoea cornuta Lamouroux, 1821). Aselomaris michaeli Berrill, 1948 and Rhizorhagium navis Millard, 1959 are regarded as synonyms and combined under the binomen Pachycordyle michaeli (Berrill, 1948). Confusion in the literature over the identity of Sertularia tenera G.O. Sars, 1874 is addressed, and distinctive characters of the species are discussed. A species often misidentified as S. tenera is assigned to Sertularia spitzbergensis (Jäderholm, 1909); the name spitzbergensis is elevated in rank from subspecific to specific, and assigned priority over its simultaneous synonym siberica Jäderholm, 1909 under the First Reviser Principle. Gonothecae of Clytia gigantea (Hincks, 1866) (type locality: Lamlash Bay, UK) are reported for the first time in material from Europe. Although much like Clytia hemisphaerica, this species is retained as valid due to its remarkably robust colony form, elongate and gradually tapered hydrothecae, and linguiform rather than wavy or pointed marginal cusps. Eudendrium album Nutting, 1896, Pachycordyle michaeli (Berrill, 1948), and the hydroid stage of Halitholus cirratus Hartlaub, 1913 are reported for the first time from the study area. A checklist of hydroids from the study area is included. © 2012 Magnolia Press.