The karyotype of the grass-carp, Ctenopharyngodon idella.

We undertook karyotype studies in the grass-carp in 1976 and in 1978.Chromosome studies were mainly carried out with cultured kidney cells;slides were made by the flame-drying method with Giemsa staining.More than 200 clear mitotio metaphase figures,of which more than 160 metaphase chromosome spreads were counted,were examined in kidney cells of the grass-carp.Each pair of homologous chromosomes in 10 karyograms was measured.We calculated in each homologous chromosome pair the percentage of TCL (total complement length),arm ratio and their mean values.C.iddlus has a diploid number of 48;its karyotype consists of 8 pairs of median centric region chromosomes and 16 pairs of submedian centric region chromosomeswith a total number of chromosome arms (arm number----AN) amount to 96.Theresults are presented in Table 1 and Figs.1-5.No subterminal centric chromosomes and terminal centric region chromosomes could be detected,and no mono-armed chromosomes either.The results obtained from the present study are different from those of the early report.Having observed and analysed the early-,full-,and late-metaphase figures,the author holds that in analysing the karyotypes,the full-metaphase should be taken as the criterion but not the late-metaphase.