Kubota S. (1984). A new bivalve-inhabiting hydroid from central Japan, with reference to the evolution of the bivalve-inhabiting hydroids. Journal of the Faculty of Science Hokkaido University, Series Vi Zoology. 23(4): 454-467.

24884

Kubota S.

1984

23(4): 454-467

Publication

A new commensal hydroid associated with Mytilus edulis was described based on the male and female specimens collected from Zagashima Island, central Japan. The newly liberated medusa with usually 2 tentacles was reared in laboratory for apprx 2 mo. and the morphological changes in the life-span were clarified. The present hydroid is different from related ones in its medusan generation from mature to spent stages. The small medusa, up to 4.5 mm in diameter, has many (up to 41) cirri, up to 4 tentacles and 26 marginal swellings including the tentacular bulbs, oval to linear gonads on the 1st half of the radial canals and up to 52 statoliths (up to 10/statocyst), but no peduncle. E. intermedia sp. nov. is assigned to the medusan generation. The present hydroid is designated Eugymnanthea inquilina inquilina Palombi, 1935-Eucheilota intermedia prior to settle the complete scientific name (binomen). The present bivalve-inhabiting hydroid belongs to the 4th group and it is an intermediate hydroid between the members of the group I (the most primitive hydroids) and the group III (the most derived ones). A paedomorphic evolution from Eutima to Eugymnathea passing through Eucheilota (progenesis) was deduced, assuming that the bivalve-inhabiting hydroids are a monophyletic group. This evolutionary change was confirmed in Japanese hydroids from the biogeographic point of view.Descriptors: EUCHEILOTA INTERMEDIA new species; EUGYMNANTHEA INQUILINA INQUILINA; EUTIMA; EUGYMNANTHEAfigs. 1-4, tabs. 1-2. (iv.1984).

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Japan

Cycles, Saisonality, Phenology
Evolution

Hydrozoa

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