Sexual dimorphism in somatic interphase nuclei of snakes

Somatic interphase nuclei of different tissues of heterogametic females of various species of snakes with a differentiated W chromosome possess a distinct, darkly stained chromocenter comparable to the characteristic mammalian sex chromatin. The absence of such a prominent body in similar tissues of homogametic males, the allocycly in the DNA replication pattern exhibited by the W, and the positive correlation between the size of the chromocenter and the size of the W in different species are the evidence from which it is concluded that the sex-chromatin body of the interphase nuclei in snakes is formed by the W chromosome of the heterogametic females. The lack of incorporation of ³H-uridine by the chromocenter indicates its inactivity. In order to distinguish this heteropycnotic body from the sex chromatin of the homogametic sex in mammals, it is suggested that it be termed “W chromatin”.

Chromosomes and the classification of the snakes of the family Boidae

The chromosomes of the Indian rock python, <i>Python molurus</i> (sub-family Pythoninae), and the sand boa, <i>Eryx johni johni</i> (Boinae), were investigated and compared with those of <i>Boa constrictor </i>(Boinae). A striking similarity of the chromosomes of <i>Boa</i> and <i>Python</i> was observed, but the karyotype of the <i>Eryx</i> was found to be different from that of the other two species. This investigation clearly supports the validity of the doubt expressed by some taxonomists regarding a close phylogenetic relationship between <i>Boa </i>and <i>Eryx</i>.