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 26

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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to non-native regions, a questionnaire survey on their occurrence in the field, including both published and unpublished records, was conducted in 2002-2003.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

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 2

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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

齋藤 暢宏 木下 今日子

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.59, pp.1-7, 2004-07-28 (Released:2009-08-07)

参考文献数

26

被引用文献数

4 4

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During a faunal survey of the intertidal mud flat of Shinhama Lagoon on the northern coast of Tokyo Bay, parasitic bopyrid isopods, Ione cornuta Spence Bate, were found attached to the inner walls of the branchial chambers of ghost shrimps, Nihonotrypaea japonica (Ortmann). In this isopod, the females are parasites of N. japonica whereas dwarf males attach to conspecific females. To investigate the prevalence of the parasite I. cornuta, sampling of ghost shrimps was conducted every 2 to 4 weeks at the Shinhama Lagoon during the periods from August, 1994, to October, 1995, and January, 1998, to May, 1999. A total of 328 individuals (253 females, 62 males, and 13 of unknown sex) of N. japonica was collected, and 22 individuals among them (6.7%) were infected with I. cornuta. Among the infected shrimps, females accounted for 21 individuals, and only one male was infected. This skewed sex ratio is considered to simply reflect the female-biased sex ratio of this species in the field. In most cases, one individual of the parasite I. cornuta was attached within the left or the right branchial chamber of each host shrimp. No significant relationship was detected between the handedness of the major cheliped of the host shrimps and the attachment position of I. cornuta. A significant positive correlation was found between the size of the host shrimps and the size of mature females (i.e., those with brood chambers) of the parasite; however, the size of immature parasites was not correlated with the size of their host shrimp. In spite of the long sampling periods during this study, no ovigerous shrimp infected by I. cornuta was collected. This strongly suggests that infection by I. cornuta negatively affects the reproduction of the host female shrimps.