Meiotic drive by the Y-linked D gene in Aedes aegypti (L.) (Diptera: Culicidae) is associated with disruption of spermiogenesis, leading to premature senescence of spermatozoa.
Y chromosome meiotic drive in the mosquito Aedes aegypti, due to the gene D (Distorter) in coupling with M (male determination) [the MD haplotype], is associated with spermiogenic disruption, leading to senescence, at a rate proportionate to male excess. Spermiogenesis was compared between 'Enhanced Mutant' males with a strongly female-depleted sex ratio (8.9% females), 'Mutant' males showing a lesser degree of distortion (38.3% females), and two controls with normal sex ratios (51.2% and 49.2% females). Sections of testes dissected from mature pupae and adults aged 0, 4, 8, 12 and 16 days were examined by transmission electron microscopy. A difference between Mutant and control spermiogenesis was apparent as early as the pupal stage when some Mutant spermatids showed extra tail elements (axonemes and/or mitochondrial derivatives). The same was true of Enhanced Mutant males but to a more extreme degree. Sperm senescence was evident in Enhanced Mutant testes from day 0 of adult life but in Mutant testes not until day 4. Progressive disorganisation was associated with many loose organelles, and disturbance of the anterior-posterior axis of gamete differentiation within the testis. Degenerative changes of a similar kind in the controls did not become apparent until day 8. These findings are discussed with respect to other characteristics of this meiotic drive system, in terms of a theory of inhibition of reduction division in spermatogenesis associated with fragmentation of the X chromosome, leading to the formation of a restitution nucleus as early as metaphase 1.
Owusu-Daaku
K O
KO
Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
Butler
R D
RD
Wood
R J
RJ
D000330:Aedes / Q000235:genetics* / Q000502:physiology*; D000818:Animals; D005260:Female; D017344:Genes, Insect; D050173:Genes, Y-Linked / Q000235:genetics / Q000502:physiology*; D008297:Male; D008540:Meiosis / Q000502:physiology*; D009154:Mutation; D013091:Spermatogenesis / Q000235:genetics / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology*