Abstract
The karyotypes of four species of Japanese Trimeresurus are described. They are similar to each other and the diploid number is 2n=56 with 16 macro- and 20 microchromosomes. In all species, the sex chromosomes of ZW type are recognized. The three species of them have the second pair similar to that of the new world pitvipers, while remaining T. okinavensis has a slightly larger arm ratio which approaches that of Asian Agkistrodon. C-banded karyotypes are described for T. flavoviridis and T. okinavensis. The latter has a portion heavily stained on the longer arms of 1st and 2nd pairs, which correspond to the secondary constrictions observed in some metaphase plates. These are not observed in the former.
