The study of the male and female karyotypes ofthe polychaete Dinophilus gyrociliatus was performedwith the aim of ascertaining the diploid number ofchromosomes and confirming the existence of karyologicaldifferences between the two sexes. Our resultsevidenced that the female karyotype of D. gyrociliatusconsists of 2n=24 chromosomes, while the male karyotypehas 2n=23 chromosomes. X chromosomes aresubtelocentric and much bigger than the autosomes. Thesize of the D. gyrociliatus chromosomes, which in thefemale embryos vary in length from little more than2.8 lm to less than 0.7 lm, are relatively small bycomparison with those of other polychaetes. The existenceof maternal and environmental factors able toinfluence the sex ratio of D. gyrociliatus and chromosomaldifferences between the sexes confirms that: (1) sexdetermination is chromosomal and syngamic of the XX–X0 type and (2) control of the sex ratio is progamic anddepends on genetic and environmental factors.
Karyotype and sex determination in Dinophilus gyrociliatus (Polychaeta: Dinophilidae) / Simonini, Roberto; Molinari, Federica; Ansaloni, Ivano; Pagliai, Anna Maria; Prevedelli, Daniela. - In: MARINE BIOLOGY. - ISSN 0025-3162. - ELETTRONICO. - 142:(2003), pp. 441-445.