Karyology of genera Calanopia and Pontellina with a note on cytotaxonomical and evolutionary relationship in family Pontellidae

U. Goswami, S.C. Goswami

Abstract



Karyological studies were made on four species of copepods viz: Calanopia aurivilli, C. elliptica, C. minor and Pontellina plumata. The diploid and haploid number of chromosomes encountered during the mitotic and meiotic divisions were 22 and 11 respectively. The karyotype formulae comprised of 7 sM + 13M + 2A ()
8 sM + 12M + 2A () in C. aurivilli, 5 sM + 14M + 3A () in C. elliptica, 1 sM + 19M + 2A () in P. plumata. The average total length of the chromosomal pairs varied between 0.52 - 1.88 mu m in C. aurivilli, 0.35 - 1.28 mu m in C. elliptica, 0.52 - 2.20 mu m in C. minor and 0.31 - 1.63 mu m in P. plumata. In all the species the sex-mechanism was of the XY-XX type with male as the heterogametic sex and distinguishable X and Y chromosomes. On the basis of chromosomal and morphological data available the cytotaxonomical and evolutionary relationship in the family Pontellidae is derived. It showed that the genera Labidocera, Pontella, Pontellopsis on one hand and Calanopia and Pontellina on the other are more closely allied. The former three genera are of recent origin and Labidocera minuta is the connecting link

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