Vp. Korablev et al., The XX-XY (male-heterogametic) sex chromosome system in Polydora curiosa (Polychaeta : Spionidae), OPHELIA, 51(3), 1999, pp. 193-201
Chromosome complements of Polydora curiosa Radashevsky, 1994 (Polychaeta: S
pionidae) were examined using air-drying method. Regenerating worm tips and
gamete-bearing segments were used for the analysis. A diploid chromosome n
umber of 34 was found in well-spread metaphase plates of somatic cells. A p
air of sex chromosomes (XY) with the Y considerably larger than the X was f
ound in males. The size and shape of the Y chromosome were individually var
iable. Sixteen normal bivalents and one large univalent-like bivalent were
observed in metaphase I plates of spermatocytes. The large bivalent is the
end-to-end association of heteromorphic sex chromosomes having very low str
uctural homology. ks many as 39% of studied spermatocytes of P. curiosa wer
e found to be tetraploid cells. The sex chromosome system described herein
is the first case of XY male heterogamety in the Spionidae and only the sec
ond one so far documented in the Polychaeta.