Freshwater Bryozoa of Okinawa, Japan, with descriptions of Rumarcanella gen nov. (Phylactolaemata: Plumatellidae) and two new species

We identified nine species of phylactolaemate bryozoans collected from ponds and dams on Okinawa Island, Japan. This is the first report on freshwater bryozoans from Okinawa and includes the first record of Plumatella javanica from Japan. Phylactolaemate species were identified on the basis of colony and statoblast morphology and are illustrated by light microscopy and scanning electron microscopy (SEM). We detected two new plumatellid species that, like Plumatella minuta and Plumatella vorstmani, have a transparent, weakly chitinized colony and hypertubercles on the floatoblast fenestra. A previous molecular study showed these four species to form a clade separate from Plumatella and Hyalinella. We here establish the new genus Rumarcanella to accommodate these species and describe Rumarcanella gusuku n. sp. and R. yanbaruensis n. sp. We discuss the dispersal of bryozoans to and from Japan by birds carrying statoblasts and provide a key to the Phylactolaemata of Japan.