Studies on gametogenesis in Tachygonetria vivipara Wedl, 1862 and Thelandros alatus Wedl, 1862 (Oxyuroidea; Nematoda) from Uromastix acanthinurus in Morocco

Abstract

Chromosome changes during gametogenesis in Thelandros alatus and Tachygonetria vivipara, pharyngodonids (Oxyuroidea; Nematoda) from Uromastix acanthinurus from Morocco, indicate that both species are haplodiploid. Meiosis was normal in females of Thelandros alatus. There were five bivalents, indicating a diploid number of 10 chromosomes. Most embryos in utero contained 5 chromosomes but one was observed with 10. Spermatogonial divisions contained five chromosomes; there was no evidence of chromosome pairing nor bivalent formation in males and divisions in the transformation zone of the testis contained five chromosomes with fuzzy outlines. There was no evidence of chromosome pairing nor bivalent formation in males of Tachygonetria vivipara. Oviparous and ovoviviparous females were examined. Three bivalents formed indicating a diploid number of six chromosomes. Chromosomes were counted in 179 embryos from 79 oviparous females; 128 were diploid (i.e., female) and 51 were haploid (i.e., male). It is suggested that the life cycle of T. vivipara resembles that of Gyrinicola batrachiensis: hosts are colonized by thick-shelled eggs, most of which develop into ovoviviparous females, and these females, if not fecundated, produce males parthenogenetically which develop in the same host. After being fecundated (sometimes by way of mother-son matings) the same females produce oviparous female progeny which develop in the same host. Eggs from oviparous females colonize a new host.