Karyological analyses on redclaw crayfish Cherax quadricarinatus (Decapoda: Parastacidae)

The karyotype of freshwater redclaw crayfish Cherax quadricarinatus (von Martens) was studied by examining metaphase chromosome spreads from the testis tissues. A total of 79 mitotic metaphases were examined and the diploid chromosome number ranged from 188 to 203 per metaphase with a mode at 200, representing 25.8% of the metaphases. The number of bivalents varied from 88 to 103 with a mode at 100, representing 54.4% of the 168 meiotic metaphases observed. The number of diploid chromosomes (2n=200) was confirmed by the modal haploid chromosome number (n=100) in the adult testis of this species. The karyotype consisted of 33 metacentric, 25 submetacentric, 14 subtelocentric and 28 telocentric chromosome pairs. The sex chromosomes, if it exist in this species, were cytologically indistinguishable.