Subfossil cyclostome bryozoans from Daidokutsu submarine cave, Okinawa, Japan

Abstract

A sediment core (Core 19) taken in Daidokutsu cave on Ie Island, Okinawa, spans the last 7,000 years. The sampling of multiple taxa from this submarine cave has been aimed at understanding the Holocene history of biodiversity and ecological dynamics. The results have already been published for ostracods, molluscs, foraminifera and cheilostome bryozoans. The current study focuses on the cyclostome bryozoan fauna, establishing a taxonomic foundation that will contribute to an understanding of responses by the bryozoan community in this cave habitat to environmental and climate changes through the Holocene. Very little has been published on modern and Quaternary fossil cyclostomes from Japan, and nearly all publications predate the routine use of scanning electron microscopy in cyclostome taxonomy. Fifteen cyclostome species are described here from Daidokutsu. Eight of these are new species, the remaining seven were identified only to the genus level. The high proportion of new species may not only reflect the uniqueness of the Daidokutsu cyclostome fauna but also the scarcity of studies on Japanese cyclostomes and the inadequacy of descriptions and figures in older publications, which make it difficult or impossible to interpret the species they describe. Unlike cyclostome cave faunas from the Mediterranean, erect cyclostomes strongly outnumber species with encrusting colonies. In addition, the secondary homonymy of Parasmittina ligulata, used for both a new species from Daidokutsu Cave and a Western Atlantic species, is resolved by renaming the Japanese species Parasmittina vieirai nom. nov.