Occurrence of Eugymnanthea sp. (Leptomedusae, Eirenidae), an evolutionary advanced species of the bivalve-inhabiting hydrozoans, from Ongael Lake, Palau Islands, associated with Brachidontes sp. (Bivalves, Mytilidae)

Abstract

One of the most evolutionary advanced species of the bivalve-inhabiting hydrozoans Eugymnanthea is recently found from Ongael Lake, Palau Islands, associated with Brachidontes sp. The morphology of mature male or spent male medusa is described, comparing with two known species of the genus, E. inquilina and E. japonica, and discussed on its taxonomic position since it shows intermediate character states between the two.