Chromosomal complements of two forms of Neanthes japonica (Polychaeta,Nereididae) with evidence of male-heterogametic sex chromosomes |
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Authors: | Sato M Ikeda M |
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Institution: | (1) Department of Biology, Faculty of Science, Kagoshima University, Korimoto, 890 Kagoshima, Japan;(2) Present address: Department of Fishery Science, Faculty of Agriculture, Tohoku University, 980 Sendai, Miyagi, Japan |
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Abstract: | Karyotypes of the brackish-water polychaeteNeanthes japonica (Izuka) collected from five rivers in Japan from 1984 to 1988 were examined with air-drying and flame-drying methods using materials consisting of regenerating tails, clumps of spermatogonia and youngN. japonica specimens (embryos, larvae or juveniles). A diploid number of 28 was determined in well-spread metaphase chromosomes of mitotic cells. The presence of an XX-XY (male heterogametic) sex chromosome system was established for the first time in polychaetes. The Y chromosome was larger than the X chromosome. Slight differences in karyotype were found between two forms (the small- and large-egg forms), which are very similar in adult morphology but can be distinguished by reproductive and developmental characteristics. |
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