Bryozoans are sessile, clonal animals; about 6,000 living species have been described. The recent study revealed approximately 1,000 species including undescribed species in Japanese waters. Diversity of bryozoans in Okinawa has been not studied in detail; only 22 species have been reported previously. The recent review of bryozoan diversity in the Nansei Islands including Okinawa estimates more than 150 species in this area; the fauna is characterized with both temperate and the Indo-Pacific species. Marine benthic environment in Okinawa varies in the characters, such as dead coral and rubble assemblage in shallow depth, sandy or muddy bottom in deeper area, and mangrove forest at estuarine area. Depends on the diverse benthic environment, bryozoans form colonies of various morphologies on different kinds of substrates such as dead coral and shells. Some bryozoans inhabit muddy bottom by forming erect or free-living colonies. Recent study on bryozoan life-history find the correlation between sand-dwelling bryozoan life-history and climatic characters such as high temperature during summer and disturbance of the water column caused by typhoon. Furthermore, specific relationships between endemic bryozoan species and other organisms in Okinawa also contribute to maintain the high diversity of benthic organisms in Okinawa. Bryozoans are suitable for further study on biogeography and speciation of marine benthic organisms, since some bryozoan species have lower dispersal ability and their distribution is limited in the small area. Taxonomic studies of highly diverse marine organisms in Okinawa have a potential to provide crucial information for development of ecological studies and protection of the organisms and their habitat in Okinawa.
Two specimens (67.5–75.1 mm standard length; SL) of Plectranthias maekawa Wada, Senou and Motomura 2018 (Serranidae: Anthiadinae), previously recorded only the Tokara Islands, Kagoshima Prefecture, Japan, were collected from Okinawa-jima and Yonaguni-jima islands, Okinawa Prefecture, Japan. The present specimens, described herein in detail, represent the first records of the species from Okinawa Prefecture. Although the body depth (% of SL) has been regarded as one of diagnostic characters between P. maekawa and two closely-related congeners (Plectranthias helenae Randall, 1980 and Plectranthias wheeleri Randall, 1980) in the original description of P. maekawa, that of the present new specimens was overlapped with the latter two species (viz., 33.5–37.7% of SL in P. maekawa, 35.5–38.7% SL in P. helenae, and 35.6–37.9% of SL in P. wheeleri). The number of serration on the margins of subopercle and interopercle in P. wheeleri and P. maekawa has also been regarded as a diagnostic character for the two species, but additional specimens described in this study showed that the number of serration changed ontogenetically, and it overlapped in the similar-sized specimens of the two species. However, the validities of other diagnostic characters given in the original description of P. maekawa are reconfirmed in this study (viz., number of pectoral-fin rays, scales on above and below lateral line, morphometrics of body width, head length, third dorsal-fin spine length, caudal-peduncle length and depth, and both coloration of fresh and preserved conditions). In addition, three specimens of P. wheeleri (71.3–83.7 mm SL) from the Okinawa Islands, are reported here as the first records of the species from Okinawa Prefecture; it has been previously recorded from Japan (Sagami Bay, and Tokara and Amami islands), Taiwan, Indonesia, and Australasia.
Accurate descriptions of distribution and habitat are important for effective We examined the distribution patterns and habitat preferences of two related gizzard shads, Nematalosa japonica and N. come, based on specimens, reports and fish market research in the Ryukyu Archipelago. Both species are N. japonica to the north of Okinawa-jima Island, and come in waters off Amami-ohshima Island and the Okinawa Islands, thereby being distributed at Amami-oshima Island and Okinawa-jima Island. Natural between the two species, found only at Okinawa-jima Island indicated that is a natural hybrid zone. Analysis using a random forest method and fish market N. japonica was most affected by tidal flat type tidal flats), the species being dominant in restricted fishing grounds (Nakagusuku and Haneji coastal waters) that include many coastal tidal flats. However, N. come fected by bottom sediment type, the species being dominant in a of fishing grounds (Kin and Nago Bays, and Nanbu-higashi, Nago-higashi, Nakijin Shioya coastal waters). Thus, the distribution pattern of the two species at OkinawaIsland was affected by environmental factors, such as tidal flat type, and area and sediments. Our findings indicated a clear discontinuity in home range between the fort (CPUE) of the two species has highly altered environments. These findings indicated that the diminution of suitable Okinawan populations of both species. Accordingly, the two Nematalosa species are as being of good indicators of the health and conservation of shallow areas, such as tidal flats. Shallow habitats should be conserved to preserve healthy populations of the two species.
This study examines the war-damage and the reconstruction planning in Nago City, Okinawa Prefecture. For example, how was the war-damage in Nago different from ones in the Japanese mainland? Then, what had the reconstruction planning been made in utter confusion? Especially, how was the land readjustment without rule of system and financial help? After that, I try to estimate and consider the land readjustment in Nago.
Approximately half of the threatened Japanese tidal-flat molluscan species live in Nansei-shoto Islets, and 84% of them (71 species) distribute in Okinawa-jima Island. Twenty-four out of 71 species are endemic or limited to Okinawa-jima. Therefore, Okinawa-jima is one of the most important habitats in Nansei-shoto for those molluscs. A vast tidal flat with an area of 1,962 ha used to exist in Okinawa-jima in 1945. However, 75% of the area has been lost by 2012 due to reclamation. After endangered species in Okinawa-jima was evaluated quantitatively, all 24 species were considered the critically endangered species. As for the tidal-flat molluscs of southern part of Okinawa-jima Island, species diversity was already decreased by coastal development for economic activities. The first extinct species of Japanese tidal-flat molluscs was recognized in Okinawa-jima Island. Natural bay areas still remain in Oura bay and Haneji naikai inland sea, northern part of Okinawa-jima. We must protect these bay areas where the threatened tidal-flat molluscs are able to inhabit.