著者
福田 宏
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.56, pp.33-41, 2001-07-15 (Released:2009-08-07)
参考文献数
37
被引用文献数
2 or 0

The present status of the molluscs of the Suô-nada Sea coast is reported, and conservation of the species diversity there is discussed. This place is exceptional in modern Japan due to its extremely high biodiversity. Few people appreciate the rich biota in these tidal-flat ecosystems, and major destruction there has already begun. For the conservation of the biota of the Suô-nada Sea, it is essential to recognize the relationships between species and their microhabitats, because the habitats of most tidal-flat species are very restricted in space. Here I discuss some major problems in the conduct of environmental assessment studies in Japan, as illustrated by research into the expected impact on the molluscan fauna of the construction of the Kaminoseki Nuclear Power Plant on Nagashima Island. These problems include misidentifications, underestimation of faunal or ecological richness, failure of artificial plantings or mitigation, misleading treatment of the concept of conservation, and emphasis on protection of only a few species useful for human beings. I also discuss the role of amateur researchers in the conservation of tidal flats. Amateurs sometimes can provide new and precise information on the status of species, which is important when there have been recent rapid changes in environmental conditions. On the other hand, amateurs must understand that many species are endangered today and should not be overhunted only for private purposes.
著者
熊川 真二 中田 和義 川井 唯史
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.66, no.1, pp.26-32, 2011-10-15 (Released:2012-10-11)
参考文献数
20
被引用文献数
1 or 0

Official documents and archives suggest that the alien crayfish Pacifastacus leniusculus (Dana, 1852) was introduced into Japan from North America on five occasions from 1926 to 1930, and populations have survived in Hokkaido, Nagano, and Shiga Prefectures. The chemical conditions and biological environment of an established habitat near their original a release point in Akashina, Azumino City, Nagano Prefecture, were surveyed on four occasions in 1998 and 1999. Water quality (pH, DO, BOD) and WT were recorded seasonally at each of eight stations, and crayfish and other aquatic macro-organisms were collected. Some predatory fishes (Oncorhynchus mykiss, Anguilla japonica, and Lepomis macrochirus) that might actively eat juveniles of P. leniusculus were recorded. Individual density of P. leniusculus was relatively low compared to its other habitats in Japan. Only 52 crayfish were collected during this study, on 19 of 32 sampling occasions (eight sites, four times each). The shape of the acumen and the species composition of ectosymbiotic crayfish worms (Annelida: Clitellata: Branchiobdellidae) can be used as tools to trace the origin of introduced of P. leniusculus in Japan. The present crayfish from Nagano Prefecture have a relatively short acumen, different from those of specimens from Shiga and Hokkaido Prefectures. Furthermore, the crayfish worm Xironogiton victoriensis occurs only on crayfish from Akashina, Nagano Prefecture. The dates of introduction of P. leniusculus in Nagano (1926, 1929) also differ from those for Hokkaido (1930) and Shiga Prefecture (1926). These findings suggest that the regional population of P. leniusculus in Nagano has a different origin than those in Shiga and Hokkaido, having originated from crayfish that were introduced independently from North America.
著者
風呂田 利夫 木下 今日子
出版者
JAPANESE ASSOCIATION OF BENTHOLOGY
雑誌
日本ベントス学会誌 = Japanese journal of benthology (ISSN:1345112X)
巻号頁・発行日
vol.59, pp.96-104, 2004-07-28
参考文献数
27
被引用文献数
3 or 0

Two introduced crab species, Pyromaia tuberculata and Carcinus aestuarii, occur abundantly in organically polluted waters in Japan. Population studies of these crabs have been conducted in Tokyo Bay, in which summer hypoxia causes destruction of the benthic animal populations on the bottom of the innerhalf of the bay. In fall, a population of P. tuberculata quickly recolonizes that bottom, which has recovered from the hypoxia, by settlement of larvae. Settled crabs reach maturity by the next spring, then release larvae until the subsequent summer hypoxia. Released larvae disperse to the outerhalf of the bay, resulting in recruitment of juveniles into the local population. These recruits reach maturity before the fall under the normoxic conditions prevailing there, then release larvae for recolonization of the innerhalf of the bay. Carcinus aestuarii grows along the shores of river-mouths and in a lagoon of the inner bay, but migrates out onto the bay bottom during fall to spring, when it releases larvae. Released larvae settle along the shores during the spring. Settled crabs grow on the shores with adult crabs that had returned from the bay bottom. Thus the crabs on the shores avoid encountering the bottom hypoxia. These results suggest that the main factor that has allowed the establishment of the new introduced populations in Tokyo Bay is complementarity between the life cycle of these crabs, including adult migration or larval dispersal, and the seasonal availability of a habitat that is recovering from hypoxia.
著者
松尾 匡敏 首藤 宏幸 東 幹夫 近藤 寛 玉置 昭夫
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.62, pp.17-33, 2007-07-25 (Released:2010-02-05)
参考文献数
88
被引用文献数
1 or 0

In April, 1997, construction of a dike in the inner part of Ariake Sound to close off the innermost area of Isahaya Bay was completed. In June of both 1991 and 2002, benthic surveys were conducted using a Smith-McIntyre grab sampler at 88 stations over the entire sublittoral area of Ariake Sound. The structure of the gammaridean amphipod assemblage was compared between 1997 and 2002 with regard to any change in grain-size composition of the substrates and dissolved oxygen concentration of the bottom waters. No noticeable changes were observed in the distribution of the median particle diameter and silt-clay content, nor in the spatial arrangement of the sediment types of the substrates. Hypoxic water masses were observed in the bottom waters in 1997 in and around Isahaya Bay and in the southern part of Ariake Sound. Other studies also recorded hypoxic water masses in the former area in 1999 and 2001. For the amphipod assemblage, a total of 12, 434 individuals of 94 species belonging to 24 families was collected in 1997; the most dominant species was Photis longicaudata (family Isaeidae). In 2002, those values had changed to 37, 649 individuals, 89 species, and 27 families, with the most dominant species being Corophium sp. A (family Corophiidae). In both years, the amphipod assemblage was dominated by six families, including Isaeidae, Ampeliscidae, Corophiidae, Priscomilitaridae, Melitidae, and Aoridae, although the dominance order changed partially. The amphipod assemblage in both years inclusive was divided into eight groups using group-averaged clustering and non-metric multidimensional scaling. The group with the highest number of stations occupied the largest bottom area, composed of poorly-sorted medium to coarse sand along the longitudinal axis of Ariake Sound; the number of stations in this group increased from 41 in 1997 to 57 in 2002. Increase in individual density and expansion of distribution range of seven species of the superfamily Corophioidea (Corophiidae, Isaeidae, Priscomilitaridae), which occurred around the two hypoxic areas, contributed most to the range extension. For the above-mentioned six most dominant families, density of individuals and proportional composition of number of individuals in each of the two hypoxic areas and other, non-hypoxic areas were compared between the two years. In particular, both values remarkably increased for several members of the Corophiidae, including Corophium sp. A and C. crassicorne, in 2002; the exception was the value for density of individuals in the southern hypoxic area. The Shannon-Wiener species diversity index values were lower in 2002 for both the two hypoxic areas and the combined non-hypoxic areas, and for the three main groups of the amphipod assemblage.
著者
土田 真二 藤原 義弘 藤倉 克則
出版者
JAPANESE ASSOCIATION OF BENTHOLOGY
雑誌
日本ベントス学会誌 = Japanese journal of benthology (ISSN:1345112X)
巻号頁・発行日
vol.58, pp.84-88, 2003-06-27
被引用文献数
4 or 1

The spatial distribution around hydrothermal vents, population structure, and relative growth parameters of the galatheid crab Shinkaia crosnieri were examined. Surveys were done by the Shinkai 2000 on the Hatoma and Dai-yon Yonaguni Knolls in the southern Okinawa Trough. On the Hatoma Knoll, S. crosnieri inhabited areas (temp. 4.0-6.2°C) about 0.2-2 m away from the active vent (temp. 301°C). In the outer area of the habitat of S. crosnieri (temp. 3.0-3.7°C), dense beds of Bathymodiolus mussels occurred and aggregations of Alvinocaris shrimp were observed. In this survey, 248 specimens of S. crosnieri were collected. Small, probably just post-metamorphic juveniles and large, mature adults co-occurred. Chelipeds of males were proportionally larger than those of females, while abdomens of females were proportionally larger than those of males. Larger chelipeds in males are thought to have evolved through male-male competition for females, and wider abdomens in females are thought to be related to the attachment of fertilized eggs to the abdominal appendages.
著者
中田 和義 永野 優季 大橋 慎平 河合 俊郎 大高 明史
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.69, no.2, pp.90-94, 2014-12-31 (Released:2016-02-06)
参考文献数
24

In Lake Akan, Hokkaido, northern Japan, the local population of the native and endangered Japanese crayfish Cambaroides japonicus (De Haan, 1841) is extinct, whereas the signal crayfish Pacifastacus leniusculus (Dana, 1852), an invasive species from North America, has become established and rapidly increased. This study provides information about specimens of C. japonicus preserved by Dr. Saburo Hatta from the lake in 1872. The six specimens (two males and four non-ovigerous females) are valuable evidence of C. japonicus formerly inhabiting Lake Akan. The body sizes of the specimens were 24.4–29.5 mm in carapace length and 55.7–67.4 mm in total length, and the estimated age of the largest specimen was ten years, indicating that Lake Akan of that time provided a suitable habitat. Twenty-two ectosymbiotic crayfish worms (Annelida, Clitellata, Branchiobdellida) were found attached to the specimens. Three branchiobdellidan species were identified: Cirrodrilus cirratus Pierantoni, 1905, C. inukaii (Yamaguchi, 1934) and C. megalodentatus (Yamaguchi, 1934). This is the first record of the latter two species from Lake Akan.
著者
岡本 直子 逸見 泰久
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.57, pp.75-78, 2002-06-27 (Released:2009-08-07)
参考文献数
8
被引用文献数
1 or 0

The reproductive strategy of the parasitic isopod Onisocryptus ovalis in the luminescent ostracod Vargula hilgendorfii was studied at a beach in Kumamoto Prefecture, Japan, and in the laboratory, mainly from April 2000 to May 2001. Onisocryptus ovalis is a protandrous hermaphroditic species and changes from a mobile male to an immobile female that loses most of its appendages and has a sack-like body. Male parasites O. ovalis invade female hosts V. hilgendorfii, eat the host eggs, change sex, produce eggs, and die after the eggs have hatched. Some parasites invade immature or male hosts, but move to female hosts immediately afterwards. The percentage of hosts parasitized by O. ovalis was low (0-18%) from summer to autumn, but increased greatly (28-91%) from winter to spring mainly because of a shortage of hosts. Usually, one or two male parasites were found in a host, and only one male of them changed sex. From winter to spring, however, up to 8 male parasites were found in a host and a maximum of five changed sex. The most adaptive parasitic strategy of O. ovalis seems to fertilize eggs as a male as many times as possible, and then to produce more eggs as the only female in a host, although these parameters are not available at present.
著者
遊佐 貴志 千葉 晋
出版者
JAPANESE ASSOCIATION OF BENTHOLOGY
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.69, no.1, pp.18-22, 2014

Member of the genus <i>Neomysis</i> inhabit estuaries or lagoons in temperate to subarctic areas and are important in the food webs of those areas, but there have been few studied of this genus in the Northwest Pacific. We examined geographical variations in the species composition of mysids including <i>Neomysis</i> in eastern Hokkaido, Japan. The species composition of mysids was classified into three groups. The first group consists of mainly <i>Neomysis mirabilis</i>, the second group consists of only <i>N. awatschensis</i>, and the third group consists of several species. These types are closely related to geographical features and salinity. This study reveals that the species compositions of mysids vary considerably between locations even though these locations at similar latitude.
著者
岩崎 敬二 木村 妙子 木下 今日子 山口 寿之 西川 輝昭 西 栄二郎 山西 良平 林 育夫 大越 健嗣 小菅 丈治 鈴木 孝男 逸見 泰久 風呂田 利夫 向井 宏
出版者
JAPANESE ASSOCIATION OF BENTHOLOGY
雑誌
日本ベントス学会誌 = Japanese journal of benthology (ISSN:1345112X)
巻号頁・発行日
vol.59, pp.22-44, 2004-07-28
被引用文献数
24 or 0

To investigate the invasion history and recent geographic distribution of marine organisms introduced to Japan or transferred domestically to non-native regions, a questionnaire survey on their occurrence in the field, including both published and unpublished records, was conducted in 2002-2003. A total of 105 taxa was reported by 94 respondents. According to three criteria, viz. known or unknown geographic origin, established invasion history, and presumed dispersal mechanisms associated with human activities, 42 taxa were designated as non-indigenous species introduced to Japan through human activities, 26 taxa as indigenous species that are distributed both in Japan and other countries but are introduced from abroad to Japan for fisheries or as fish bait, 20 taxa as cryptogenic species which are not demonstrably native or introduced, two taxa as non-indigenous species that have extended their range to Japan through natural dispersion, and one taxon as an indigenous species. The remaining 14 taxa were considered to have been transferred domestically to new areas. Analysis of the years of first record of 42 non-indigenous species suggests that the rate of invasion has increased over the past century, with seven or eight species being introduced per decade after 1960. Data on temporal change in geographic distribution revealed that many non-indigenous species have become widespread recently, from the Pacific coasts of central Japan to the coasts of the Sea of Japan or northward. However, the species listed in the present study are not exhaustive, and more extensive investigations covering all taxa and all presumed dispersal mechanisms are urgently needed before consideration of legislative management of introduced marine organisms.
著者
大隅 大 弥益 輝文
出版者
JAPANESE ASSOCIATION OF BENTHOLOGY
雑誌
日本ベントス学会誌 = Japanese journal of benthology (ISSN:1345112X)
巻号頁・発行日
vol.55, pp.9-14, 2000-07-25

Specimens of the nudibranch Gymnodoris nigricolor were found on the fins of three gobiid fish species, Amblyeleotris ogasawarensis, Ctenogobiops pomastictus, and C, feroculus, near Oujima and Sesoko Islands, Okinawa, in February and May, 1994. These gobiids inhabit the burrows of snapping shrimps. The nudibranchs could be found attached to any fin (caudal, dorsal, pectoral, anal, and pelvic fins) of these fish, and they appeared to feed on a portion of the fin membrane together with one or two of the adjacent fin rays. In the laboratory, G. nigricolor also attached to a free-living gobiid fish, Bathygobius cocosensis. Nudibranchs gathered in glass tubes that had been used as refuges by A. ogasawarensis and C. pomastictus. This suggests that the nudibranchs were attracted to substances that had originated from the fish and remained in the tubes. The nudibranchs did not always attach to the fins of test fish, and individuals that did so detached themselves 1-2 days later. Their association with the fish thus appears to be a predator-prey interaction. Spawning of Gymnodoris nigricolor was observed in a rearing tank. About 200-700 eggs of 0.15 mm in diameter were found in each egg mass. Embryos hatched 10-11 days after oviposition at 24°C.
著者
大隅 大 弥益 輝文
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.55, pp.9-14, 2000-07-25 (Released:2009-08-07)
参考文献数
3
被引用文献数
1 or 0

Specimens of the nudibranch Gymnodoris nigricolor were found on the fins of three gobiid fish species, Amblyeleotris ogasawarensis, Ctenogobiops pomastictus, and C, feroculus, near Oujima and Sesoko Islands, Okinawa, in February and May, 1994. These gobiids inhabit the burrows of snapping shrimps. The nudibranchs could be found attached to any fin (caudal, dorsal, pectoral, anal, and pelvic fins) of these fish, and they appeared to feed on a portion of the fin membrane together with one or two of the adjacent fin rays. In the laboratory, G. nigricolor also attached to a free-living gobiid fish, Bathygobius cocosensis. Nudibranchs gathered in glass tubes that had been used as refuges by A. ogasawarensis and C. pomastictus. This suggests that the nudibranchs were attracted to substances that had originated from the fish and remained in the tubes. The nudibranchs did not always attach to the fins of test fish, and individuals that did so detached themselves 1-2 days later. Their association with the fish thus appears to be a predator-prey interaction. Spawning of Gymnodoris nigricolor was observed in a rearing tank. About 200-700 eggs of 0.15 mm in diameter were found in each egg mass. Embryos hatched 10-11 days after oviposition at 24°C.