Meiosis in Haematopinus suis and Menacanthus stramineus (Phthiraptera, Insecta)

Haematopinus suis (Anoplura) and Menacanthus stramineus (Mallophaga) have been cytogenetically analyzed. Both species have 2n = 10. holokinetic chromosomes. and achiasmatic male meiosis. Bivalents orientate with their long axis perpendicular to the spindle fibers at metaphase I, and first anaphase is reductional. As in other species of Phthiraptera. male gametogenesis follows a particular pattern: each cell entering meiosis results in a cyst of 64 (in H. suis) and 32 (in M. stramineus) spermatozoa and 64/32 non-functional cells ( = pycnotic nuclei). The results are compared with those previously reported for Phthiraptera, and a new terminology for the different stages of male gametogenesis is proposed. The low chromosome number together with the achiasmatic nature of male meiosis and the mitotic divisions that follow meiosis may restrict the potential for genetic variability. This might be related to the high host specificity of these parasites.