Original Articles
Investigations of the present status of threatened molluscan species in Okinawa Prefecture, southwestern Japan, for the second revision of the Red Data Okinawa ó1. Yonaguni Island
Hirofumi KUBO, Hiroshi FUKUDA, Yoshimasa HAYASE, Yuichi KAMEDA, Hiroyuki OZAWA and Rei UESHIMA
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Summary For the second revision of the Red Data Okinawa (RDO), we surveyed the present status of threatened molluscan species (chiefly terrestrial and freshwater ones) in some islands of Okinawa Prefecture. This article is the results of an investigation in Yonaguni Island. In total 53 species were found. Among them, 14 of them are regarded as endemic to the Island, but most of them were rarely found and should have rapidly decreased in recent years. On the other hand, seven unidentified species were recorded for the first time: Angustassiminea sp., Paludinellassiminea sp., Discoconulus sp. A, "D." sp. B, Parakaliella cf. bimaris (Pilsbry & Hirase, 1904), Yamatochlamys sp., Helicarionidae gen. & sp. |
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Key words: gastropods, bivalves, land snails, freshwater molluscs, fauna, biodiversity, endangered species, conservation, endemic species, alien species, Yaeyama Islands, Nansei Islands, Ryukyu Archipelago |
Investigations of the present status of threatened molluscan species in Okinawa Prefecture, southwestern Japan, for the second revision of the Red Data Okinawa ó2. Iriomote Island
Hirofumi KUBO, Koji NISHIGAKI and Hiroyuki OZAWA
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Summary This is the second report of surveys of threatened molluscan species in Okinawa Prefecture for the second revision of the Red Data Okinawa (RDO). This article shows the results in Iriomote Island. In mangrove swamps of estuaries, some new localities of endemic and/or threatened minute truncatelloidean species (e.g. Coliracemata katurana, "Rugapedia" sp., Ditropisena sp.) were found. An alien species Taiwanassiminea bedaliensis was also found for the first time in the Island. In the Urauchi River estuary, the present status of an endemic and undescribed venerid Meretrix sp. and other accompanied bivalves was investigated, but only one live individual of M. sp. was found. In Funaura, several live individuals of a rare bivalve Gari togata were found, but the density was less than half of the 2010 surveys. |
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Key words: gastropods, bivalves, molluscs, mangrove swamps, tidal flats, fauna, biodiversity, endangered species, conservation, endemic species, alien species, Yaeyama Islands, Nansei Islands, Ryukyu Archipelago |
Investigations of the present status of threatened molluscan species in Okinawa Prefecture, southwestern Japan, for the second revision of the Red Data Okinawa ó3. Kita-daito and Minami-daito islands
Hirofumi KUBO, Hiroshi FUKUDA, Yoshimasa HAYASE, Yuichi KAMEDA, Taiji KUROZUMI and Rei UESHIMA
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Summary This is the third report of surveys of threatened molluscan species in Okinawa Prefecture for the second revision of the Red Data Okinawa (RDO). This article shows the results in Kita-daito and Minami-daito island in the Daito Islands. In total 42 species were found. Among them, 29 of them are native and nine species and one subspecies are regarded as endemic to the Islands. Nesiohelix omphalina omphalina and N. o. bipyramidalis are representative endemic land snails of the Islands, but they have rapidly decreased in recent years and critically endangered. Zaptyx daitojimana was not found alive in the present survey and it has presumably become extinct already. On the other hand, unidentified species of Angustassiminea and Truncatella were recorded in the Islands for the first time. |
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Key words: gastropods, land snails, freshwater snails, fauna, biodiversity, endangered species, conservation, endemic species, alien species, Daito Islands, Nansei Islands, Ryukyu Archipelago |
Towards a taxonomic revision of the Truncatellidae (Caenogastropoda: Truncatelloidea) of Japan
Hiroshi FUKUDA, Yuichi KAMEDA, Takahiro HIRANO, Hirofumi KUBO, Yoshimasa HAYASE and Takumi SAITO
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Summary This is a preliminary report for the taxonomic revision of the Japanese Truncatellidae. Based on characters of the shells and opercula, nine species were recognized: Truncatella cf. guerinii A. & J.B. Villa, T. oagariensis (Kuroda), T. pfeifferi Martens, and six unidentified species of the genus Truncatella. Each species is distinguishable in shell size, the number of the axial ribs on the teleoconch, the presence/absence of the fasciole, and so on. Also, these nine species can be classified into two groups by the presence/absence of the axial ribs on the protoconch and the calcium deposits on the operculum. Truncatella pfeifferi is distributed in the temperate region from southern Hokkaido to Kyushu, and all other species are found in subtropical (especially in the Nansei Islands). All species except for Truncatella cf. guerinii are endangered or near threatened species due to recent habitat destruction. Truncatella oagariensis and five unidentified species are known only in one or a few localities and restricted to extremely narrow distribution ranges. |
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Key words: Truncatella, Gastropoda, taxonomy, biodiversity conservation, endangered species, supratidal zone, land snail |
New records of Gyraulus sp. (Gastropoda: Planorbidae) in Ishigaki and Iriomote islands
Takumi SAITO, Takahiro HIRANO, Shota UCHIDA and Daishi YAMAZAKI
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Summary Gyraulus sp. (previously misidentified as G. pulcher (Mori, 1938); Japanese name: Hime-hiramaki-mizu-maimai) was found in Ishigaki and Iriomote islands, Okinawa Prefecture. Hitherto, this species was recorded from Honshu, Shikoku, Tsushima Island, and the island parts of Tokyo Prefecture. The present records extend the western and southern limits of the conventional distribution range of the species. In addition, live individuals of the species have never been recorded in the Nansei Islands before, and thus this is a noteworthy finding for biogeography of the species. |
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Key words: Endangered species, Hygrophila, Gyraulus pulcher, Okinawa Prefecture, Nansei Islands |
New records of the Ferussaciidae (Gastropoda: Achatinoidea) in the Nansei Islands, southwestern Japan
Takahiro HIRANO, Shota UCHIDA, Jamen Uiriamu OTANI, Takumi SAITO, Daishi YAMAZAKI and Shin-ichiro WADA
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Summary An unidentified species of the Ferussaciidae is recorded in Miyako and Iriomote islands, Okinawa Prefecture. The record of this family in Japan was known only from the Ogasawara Islands. The present records are likely to be the first one of the family in the Nansei Islands. |
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Key words: introduced species, land snails, biodiversity conservation, Miyako Island, Iriomote Island, Okinawa Prefecture, Ryukyu Archipelago |
A study on the reproduction and growth ratio of Bekkochlamys sp. (Helicarionidae) from Ogimi-son, Okinawa Prefecture, southwestern Japan
Yoshimasa HAYASE
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Summary Very few studies have been conducted on the reproduction and growth ratio of terrestrial molluscs in Japan, except for some species of clausiliids. A living juvenile specimen of Bekkochlamys sp. (undescribed species) was sampled from Mt. Nekumachiji, Ogimi-son, Okinawa Prefecture, Japan. This specimen grew up into a mature adult in February 2016 in a breeding container, and then it spawned several times mainly during winter to spring probably by self-fertilization. These eggs hatched out three to four weeks later and some of them developed to small juveniles, but none grew up to adults on this study. Based on the detailed records of its reproduction and growth by this study and field observations on wild individuals by the others, it is suggested that Bekkochlamys sp. may be an annual species and die in autumn. |
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Key words: terrestrial molluscs, gastropods, self-fertilization, spawn, hatch, life cycle, endangered species, Mt. Nekumachiji, Okinawa Island |
Patterns of distribution and domestic introduction of Satsuma mercatoria (Pfeiffer, 1845) (Gastropoda: Camaenidae) and allied species in Japan
Yuichi KAMEDA
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Summary Satsuma mercatoria (Pfeiffer, 1845) is regarded as native to the central Ryukyu Archipelago, southwestern Japan, and has been introduced to several islands in recent years. This species likely comprises several cryptic taxa, but its taxonomic entity and the identities of introduced populations are still unclear. By examining several hundred specimens, I found that S. mercatoria likely encompasses at least three species, which can be recognized by genital morphology. Two of them widely occur in the central Ryukyu Archipelago, and likely correspond to S. mercatoria and S. miyakoensis, respectively. The rest is an undescribed species endemic to Tonaki and Kerama islands. Outside the native distribution range, Chichijima (Ogasawara (Bonin) Islands), Iheya, Minamidaito, and Miyako islands are inhabited by only S. miyakoensis, and S. mercatoria has been found in Hachijo, Yonaguni, and Kitadaito islands. In Hachijo Island, another alien species S. oshimae was also collected sympatrically. In Yonaguni Island, S. miyakoensis was dominant until the middle 2000s, but has likely been replaced by S. mercatoria during the last decade. Considering that the artificial migration also occurs within their ranges, these species may frequently be exposed to ecological/reproductive interference throughout their distributions. |
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Key words: domestic introduction, Satsuma mercatoria, Satsuma miyakoensis, Satsuma oshimae, land snails, Nansei Islands |
The first occurrence record of Cassidula schmackeriana Moellendorff, 1885 (Eupulmonata: Ellobiidae) in Iriomote Island
Takumi SAITO, Takahiro HIRANO, Shota UCHIDA and Daishi YAMAZAKI
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Summary Two live individuals of Cassidula schmackeriana were found in a mangrove swamp of Iriomote Island. The species in Japan has been recorded only from Ishigaki Island. The present record is the first formal one of this species in Iriomote Island. The situation of the habitat is reported. |
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Key words: endangered species, biodiversity conservation, mangrove, salt marsh, Okinawa Prefecture |
Non-marine molluscan fauna of Tonaki Island, Okinawa Prefecture, southwestern Japan
Hiroshi FUKUDA, Masaru AOYAGI and Yuichi KAMEDA
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Summary The non-marine molluscan fauna of Tonaki Island, in the middle part of the Ryukyu Archipelago, has been little known, although the island has residents and is not hard to access. We compiled it for the first time on the basis of literature records and our own field surveys. 45 gastropod (24 land, 13 supratidal and 8 freshwater ones) and 1 freshwater bivalve species are listed herein. The island was believed to have poor non-marine molluscan fauna with no endemic species, but Satsuma sp. (aff. S. mercatoria) is an undescribed species that is probably endemic to the present island and the Kerama Islands. Seven endangered/vulnerable species (Platyrhaphe hirasei, Cipangopaludina laeta, Stenomelania juncea, Truncatella sp., Aegista lepidophora, Satsuma sp. and Sphaerium okinawaense) are also recorded. On the other hand, some species that are commonly found in the other islands of the Ryukyus (e.g. Georissa luchuana, Cyclophorus turgidus, Ovachlamys fulgens) are restricted to very narrow range in the present island chiefly because of mountain burning around 1887. The unique histories of the recent reduction in land snail diversity and the scarcity of faunal investigations in the island are also reviewed. Both of them are likely to have been caused by people's fear of an extreme abundance of a poisonous snake Protobothrops flavoviridis in the island. |
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Key words: land snails, freshwater molluscs, gastropods, bivalve, Satsuma, Protobothrops flavoviridis, deforestation, biodiversity conservation, natural history, Ryukyu Archipelago |