Rocky-intertidal cheilostome bryozoans from the vicinity of the Sesoko Biological Station, west-central Okinawa, Japan

Abstract

ABSTRACTTo complement previous studies on the diversity of cheilostome bryozoans (Bryozoa: Gymnolaemata: Cheilostomata) in the rocky-intertidal habitat in the North Pacific, we sampled rocky substrata at three sites on the subtropical East China Sea coast of Okinawa, Japan (26°N). We examined 651 colonies or colony fragments by light microscopy or scanning electron microscopy (SEM). The range in single-site richness was 16–36 species, with 52 species detected overall. We provide descriptions and illustrations for all species, including 11 (21.2%) new species (Thalamoporella karesansui, Crassimarginatella eremitica, Hippothoa petrophila, Stephanotheca fenestricella, Calyptotheca sesokoensis, Fenestrulina parviporus, Arthropoma harmelini, Rhynchozoon maculosum, Rhynchozoon lunifrons, Rhynchozoon ryukyuense, and Rhynchozoon scimitar) and 34 (65.4%) new records for Japan. Species were patchy in local distribution, with 53.8% detected at only one among the three sites, and often rare, with 34.6% represented by only one or two specimens. Most species (94.2%) were encrusting, forming two-dimensional, sheet-like colonies or (in two cases) branching uniserial networks; three species formed small, recumbent colonies. Ascophoran-grade species (82.7%) outnumbered anascan-grade species (17.3%). Biogeographically the fauna we examined is characteristic of the Central Indo-Pacific (CIP) realm of Spalding et al.: among 40 previously described species with distributions known outside the study area, 36 (90.0%) occur in the CIP realm, and 11 (27.5%) are restricted to it. In contrast, only seven species (17.5%) have been reported from the Temperate Northern Pacific realm, including two putatively cosmopolitan species. The high proportion (86.5%) of new records for Japan (including the new species) suggests that the marine bryozoan fauna in far-southern Japan remains largely unexplored. Given that many species were rare or uncommon in the study area and/or patchily distributed among the three sites, further sampling at additional intertidal sites in the Sesoko area will likely detect higher total local richness than the 52 species we found.http://www.zoobank/urn:lsid:zoobank.org:pub:9FD78C14-60AA-44A9-A9A2-3258E5770D31