The sex ratio (F:M) in the same population of oyster, Crassostrea gigas at the commencement of the study (2007) was 1:1.0, but changed to 1:2.8 by the end of the study (2008). The sex reversal rate in two-year-old oysters was 40.2%. Specifically, female to male sex reversal rate was 66.1%, which is higher than the male to female sex reversal rate of 21.1%. The sex reversal pattern of C. gigas a...

Amphibians have been widely used to study developmental biology due to the fact that embryo development takes place independently of the maternal organism and that observations and experimental approaches are easy. Some amphibians like Xenopus became model organisms in this field. In the first part of this article, the differentiation of the gonads in amphibians and the mechanisms governing thi...

Sexual differentiation in birds is controlled genetically as in mammals, although the sex chromosomes are different. Males have a ZZ sex chromosome constitution, while females are ZW. Gene(s) on the sex chromosomes must initiate gonadal sex differentiation during embryonic life, inducing paired testes in ZZ individuals and unilateral ovaries in ZW individuals. The traditional view of avian sexu...

Sex-role reversal occurs when females compete more intensely than males for access to mates. In this paper, we survey the occurrence of sex-role reversal in vertebrates: we focus on behavioural aspects of sex-role reversal and we examine possible endocrinological correlates of this phenomenon. The best documented cases among vertebrates of sex-role reversal occur in fish and birds. In nearly al...

Mutations in the Y linked testis determining gene SRY cause 46,XY sex reversal. However, only about 15% of cases of 46,XY sex reversal are accounted for by mutations in SRY. In this study we have investigated the possibility that mutations affecting the expression of SRY might cause some of the cases of sex reversal in which the coding sequence of SRY is normal. We have screened 2 kb of DNA imm...

The Y chromosome from certain populations of M. m. domesticus is incapable of normal testis determination in the B6 inbred strain resulting in XY hermaphrodites or XY females (XY(DOM) sex reversal). B6 consomic strains have been developed with either transient (B6-Y(AKR)) or severe (B6-Y(TIR)) XY(DOM) sex reversal. We report that a point mutation, the dominant white spotting oncogene allele, Ki...