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Namikawa, H., 1991. A new species of the genus Stylactaria (Cnidaria, Hydrozoa) from Hokkaido, Japan. Zool. Sci. 8 4: 805-812.
A new species of athecate hydroid, Stylactaria multigranosi sp. nov., is described based on specimens from Hokkaido, Japan. Of 416 colonies collected, all of the mature ones (N = 306) were female. Hydroids of S. multigranosi were associated exclusively with a gastropod, Nassarius multigranosus (Dunker, 1847), living on sandy-mud bottoms. This new species is characterized by having fixed eumedusoid gonophores without marginal tentacles. Eggs is S. multigranosi develop into planulae within the gonophores. Four types of zooids (gastrozooids, normal gonozooids, non-hypostomed gonozooids and tentaculozooids) were discovered. The taxonomy of Stylactaria is briefly discussed, with particular reference to morphology of gonophores and intercolonial variation in zooid polymorphism. Descriptors: STYLACTARIA MULTIGRANOSI new species, Hydractinia multigranosi figs. 1-3, tabs. 1-7. (viii.1991).