|Chromosomal complements of two forms of Neanthes japonica (Polychaeta, Nereididae) with evidence of male-heterogametic sex chromosomes|
Sato, M.; Ikeda, M. (1992). Chromosomal complements of two forms of Neanthes japonica (Polychaeta, Nereididae) with evidence of male-heterogametic sex chromosomes. Mar. Biol. (Berl.) 112(2): 299-307
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Chromosomes; Cytology; Genetics; Karyotypes; Neanthes japonica (Izuka, 1908) [WoRMS]; Fresh water
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Karyotypes of the brackish-water polychaete Neanthes japonica 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 young N. 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.