Kulathinal Rob, Singh Rama S
Department of Biology, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.
Evolution. 1998 Aug;52(4):1067-1079. doi: 10.1111/j.1558-5646.1998.tb01834.x.
In accordance with Haldane's rule, hybridizations between species of the Drosophila simulans clade produce fertile females but sterile males. In this study, a comprehensive characterization was undertaken on the six types of F males that were the result of the crosses between D. simulans, D. sechellia, and D. mauritiana. With the use of light and electron microscopy, it was shown that while each particular hybrid genotype exhibited a specific sterility phenotype, these phenotypes fell into two distinct classes. The two hybrid genotypes that possessed D. mauritiana X-chromosomes contained spermatogenic defects that caused arrests in premeiotic spermatogenic stages. The other four F hybrids possessed postmeiotic spermatogenic defects. Nonsynchronous cell divisions, underdeveloped mitochondrial derivative-axonemal associations, and microtubule abnormalities were common to all of these hybrids. Each particular postmeiotically defective hybrid genotype demonstrated characteristically distinct profiles in sperm bundle number in addition to characteristic spermiogenic arrests in the furthest developed spermatids. These results in species hybrids contrast with the absence of significant differences in spermatogenic characters between species of this clade. In addition, by utilizing an attached-X cross, we investigated the influence of maternal effects and cytoplasmic factors on the sterility of D. simulans F hybrids and found none. However, we discovered a strain of D. simulans (2119) that caused a large shift in sterility from postmeiotic to premeiotic when crossed to D. sechellia. This suggests that D. simulans is polymorphic for genes involving premeiotic and postmeiotic sterility and that the two types of sterilities between species may have a simple genetic basis.
根据霍尔丹法则，拟果蝇进化枝物种间的杂交产生可育雌性和不育雄性。在本研究中，对拟果蝇、塞舌尔果蝇和毛里求斯果蝇杂交产生的六种类型的F雄性进行了全面表征。通过光学显微镜和电子显微镜观察发现，虽然每种特定的杂交基因型都表现出特定的不育表型，但这些表型可分为两个不同的类别。拥有毛里求斯果蝇X染色体的两种杂交基因型存在生精缺陷，导致减数分裂前的生精阶段停滞。其他四种F杂交种存在减数分裂后的生精缺陷。所有这些杂交种都存在细胞分裂不同步、线粒体衍生物-轴丝联合体发育不全以及微管异常的情况。除了在发育最成熟的精子细胞中出现特征性的精子发生停滞外，每种特定的减数分裂后有缺陷的杂交基因型在精子束数量上也表现出特征性的明显差异。这些物种杂交的结果与该进化枝物种间在生精特征上没有显著差异形成对比。此外，通过利用附着X杂交，我们研究了母体效应和细胞质因子对拟果蝇F杂交种不育性的影响，未发现有影响。然而，我们发现了一种拟果蝇品系（2119），当它与塞舌尔果蝇杂交时，不育性从减数分裂后大幅转变为减数分裂前。这表明拟果蝇在涉及减数分裂前和减数分裂后不育的基因上具有多态性，并且物种间的两种不育类型可能具有简单的遗传基础。
