Present state of imposex in neptune whelk Neptunea arthritica inhabiting shallow waters around Hokkaido, Japan |
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Authors: | Katsuaki Fujinaga Anthony S Ilano Hirotaka Nomura Richard T Miranda Shigeru Nakao |
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Affiliation: | Faculty of Social Welfare, Dohto University, 149 Nakanosawa, Kitahiroshima, Hokkaido 061-1196, Japan,;Marine Biology Section, Biology Department, University of San Carlos, Technological Center, 6000 Cebu City, Philippines,;Central Laboratory, Marine Ecology Research Institute, 300 Iwawada, Onjyuku-machi, Chiba 299-5105, and;Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1, Minato-cho, Hakodate, Hokkaido 041-8611, Japan |
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Abstract: | ABSTRACT: The state of imposex in Neptunea arthritica from seven sites along the coast of Hokkaido, Japan was examined in 2002 based on the criteria: (i) relative penis size index (RPSI); (ii) imposex frequency; (iii) stage frequency distribution of imposex in adult and immature whelks; and (iv) sex ratio. RPSI differed from site to site, although values from all sites were low (0.186–5.294). In particular, the RPSI values for four sites were very low (<1.0). In sites where immature whelks were also collected, the frequency of imposex was considerably lower in immature (7.7%–55.6%) than in adult whelks (50%–95.2%) except at one site. The imposex stage frequency distribution also differed among sites, and the trend in the adult whelks corresponded with their RPSI value. Female whelks showing severe imposex (Stage 3 and 3+) were restricted to large individuals. |
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Keywords: | Hokkaido imposex Neptunea arthritica shallow waters tributyltin |
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