The Karyology ofTisbe Reluctans(Copepoda, Harpacticoida)

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Abstract
The diploid chromosome number, 2 n = 24, has been established, in both sexes of the harpacticoid copepod Tisbe reluctans. The chromosomes are metacentric or submetacentric and differentiated sex chromosomes are not present. In the male chiasmatic bivalents form at metaphase I. In the female, during the first meiotic division and before the diffuse stage, homologous chromosomes are closely associated so that chiasmata may occur. After the diffuse stage, the homologues separate but remain parallel and juxtaposed to each other till metaphase I. The chromosomes seem to have doubled into two chromatids during the post-diffuse stage.