Conventional Giemsa and C-Banded Karyotypes of Schistosoma mansoni and S. rodhaini

Abstract

The karyotypes of a Puerto Rican strain of Schistosoma mansoni and a Kenyan strain of S. rodhaini are similar in number of general morphology. For each species there are eight pairs of chromosomes (2n =16) which are divided into three size groups. C-banded methods revealed, in addition to centromeric heterochromatin, a large heterochromatic block in one for the No. 2 chromosomes in females but not in the other. Neither No. 2 chromosome of males possessed the heterochromatic block. This pair (2) is interpreted as the sex chromosomes, with the female being heterogametic (ZW), the male homogametic (ZZ). Differences between karyotypes of the two species occurred. These included a satellite on the No. 3 chromosome of S. mansoni and a euchromatic tip on the otherwise heterochromatic short arm of the W chromosome of this species; neither of these was present in S. rodhaini. The two species also differed in that the centromeric index of the Z of S mansoni was smaller than that of the W, whereas in S rodhaini the reverse was true. In S. mansoni the large heterochromatic block of the W chromosome was identified in prophase and interphase nuclei as well as at metaphase.