Redescription of Stylactaria conchicola (Yamada, 1947), comb. nov. (Hydrozoa: Hydractiniidae) from Hokkaido, Japan

Abstract

Stylactaria conchicola (Yamada), comb . nov ., a highly polymorphic athecate hydroid, is redescribed based on specimens collected from the type locality (Muroran) and a new locality (Oshoro) in Hokkaido, Japan . Three new types of zooids (thick-gastrozooid, non-hypostomed gonozooid and tentaculozooid) are described in addition to the two types of known zooids (slender-gastrozooid and normal gonozooid) . The non-tentaculate gonozooid originally described as the third zooid type is considered a normal gonozooid being degenerated under rearing conditions . Aberration of gastrozooids is also described and briefly discussed in terms of zooid differentiation . Intercolonial variation of zooid composition is presented and its significance in species identification is discussed . Nematocyst composition and morphology of gametes are also described . S. conchicola is substrate specific ; all of the 78 colonies examined were found on the shells of living gastropods, Homalopoma amussitatum (Gould, 1861) .

A review of bipolarity concepts: History and examples from Radiolaria and Medusozoa (Cnidaria)

“…There are now a significant number of well-qualified articles on the systematics of Cnidaria based on material obtained from the surface to abyssal depths from different regions and zoogeographical provinces of the World Ocean, from the Arctic to the Antarctic. A species list of Medusozoa based on the material in the large collections of the Zoological Institute of the Russian Academy of Sciences is now available in our database, along with a list of publications that are relevant to our bipolarity discussion (Briggs 1928(Briggs , 1938Hyman& Vervoort 1986Antsulevitch 1987;Campbell 1987Campbell , 1989Rees & Vervoort 1987;Jarms 1988Jarms , 1990Jarms , 1991Jarms , 1994Jarms , 1997Larson & Fautin 1989;Margulis 1989;Stepanjants & Lobanov 1989;Brinckmann-Voss et al 1989;Gibbons & Riland 1989;Stepanjants et al 1990Stepanjants et al , 1996Stepanjants et al , 1997aStepanjants et al ,b, 1998Stepanjants et al , 1999aNamikawa et al 1990Namikawa et al , 1992Beshbeeshy 1991;Larson et al 1991;Namikawa 1991;Ryland & Gibbons 1991;Svoboda & Cornelius 1991;Yamada & Kubota 1991;Boero & Hewitt 1992;Kubota & Takashima 1992;Pages et al 1992;Ramil & Vervoort 1992;Antsulevitch & Vervoort 1993;Boero & Bouillon 1993a,b;…”

Reconciling genealogical and morphological species in a worldwide study of the Family Hydractiniidae (Cnidaria, Hydrozoa)

“…H. antonii has a calcified skeleton that is very different from the calcified skeleton in the distantly related hydractiniid Janaria ( see discussion below). In the same clade, though, is the Japanese S. conchicola , which has entirely reduced sporosac reproductive structures, and has opposite host‐specificity to H. allmanii , being only found on the living gastropod Homalopoma sagarensis in Hokkaido, Japan (Yamada 1947; Namikawa et al . 1992; Hirohito 1988).…”