Multiple sex-chromosomes in the common Indian Krait, Bungarus caeruleus Schneider

Abstract

The highly poisonous common Indian Krait, Bungarus caeruleus of the family Elapidae has 2n ♂=44 and 2n ♀=43. There is a sharp difference in size between macro and microchromosomes. The number of macrochromosomes is 24 in males and 23 in females whereas there are 20 microchromosomes in both the sexes. The difference in number of macro-chromosomes in the two sexes is explainable on the basis of translocation of a macro-autosome to the W chromosome resulting in a multiple sex-chromosome constitution of Z₁Z₁Z₂Z₂♂/Z₁Z₂W♀-types. Autoradiographic studies using H³-TdR show that the W is late replicating except for the translocated part which finishes its replication along with the macroautosomes. This is the first example of a multiple sex-chromosome complex in a vertebrate with female heterogamety.