Chromosomal Heteromorphism In Treron Phoenicoptera

Cytological studies were carried out on Himalayan green pigeon, Treron phoenicoptera (Columbidae : Columbiformes : Aves). Sixteen males and twelve females were sacrificed and their bone-marrow cells extracted through a sternal puncture. Cells were treated in hypotonic saline, fixed in 1:3 aceto-alcohol and stained in Giemsa. Chromosomes were classified according to Levan et al (1964). In all, one hundred thirty three cellular plates were examined and the modal diploid count was found to be 76+3. There were seven pairs of macrochromosomes, including a pair of sex element (ZZ in case of male and ZW in case of female individuals). All, with clearly defined size and centromeric position, could be easily recognized. A total number of thirty-one pairs formed a gradated series of elements, whose morphology could not be resolved, and have been included in the category of microchromosomes. They comprised 45.6% of TCL. Both the sex chromosomes - Z & W has centromeres at their median point, however, Z is a macrochromosome { Relative Length (LR) = 11.82% ; IC = 49.19 }, whereas, W is the largest microchromosome (LR = 6.67% ; IC = 40.45). Among the twenty eight adult individuals examined, eight karyotypic combinations, irrespective of sex, were observed. In majority of cases, chromosome I and II had centromere in their median region. However, owing to gradual shift in the position of centromere, 8 different chromosome morphs ( Im Im IIm IIm, Im Im IIm IIst, Im Im IIst IIst, Im Ist IIst IIst, Ist Im IIm IIm, Ist Ist IIm IIm, Ist Ist IIst IIm, Ist Ist IIst IIst ) were encountered. According to Garg & Garg [1] [2] [3] [4] [5] [6] [7] [8] [9] and Garg et. al., [10] [11] [12], presence of such widespread inversion polymorphism in Treron phoenicoptera suggests that it may confer an adaptive advantage on the species.