Hurst GDD, Walker LE, Majerus MEN
Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, United Kingdom
J Invertebr Pathol. 1996 Nov;68(3):286-92. doi: 10.1006/jipa.1996.0098.
Adalia bipunctata, the two spot ladybird, carries a vertically transmitted bacterial agent which kills male progeny during embryogenesis. Some matrilines of A. bipunctata give rise to strongly female-biased sex ratios. 16S rDNA sequence analysis revealed a bacterium of the genus Rickettsia associated with this trait, a conclusion which is corroborated here. Using light microscopy, an association between a bacterium located in A. bipunctata hemocyte cytoplasm and matrilines which show the sex ratio trait was found. This element was not found in hemocytes taken from females from normal sex ratio lines, nor in hemocytes taken from males. The association is confirmed by study of the inheritance of the sex ratio trait. Only daughters of sex ratio crosses that bear this cytoplasmic bacterium also show the sex ratio trait, with other daughters being normal with respect to sex ratio. Transmission electron microscopy of hemocytes revealed a walled bacterium, bearing features of members of the genus Rickettsia, free in the cytoplasm of hemocytes taken from infected lines, but not in those taken from uninfected lines.
二斑叶螨（Adalia bipunctata），即二斑瓢虫，携带一种垂直传播的细菌病原体，该病原体在胚胎发育过程中杀死雄性后代。二斑叶螨的一些母系产生强烈偏雌的性别比例。16S rDNA序列分析揭示了一种与该性状相关的立克次氏体属细菌，本文证实了这一结论。通过光学显微镜观察，发现位于二斑叶螨血细胞细胞质中的一种细菌与表现出性别比例性状的母系有关。在正常性别比例品系的雌性血细胞中，以及在雄性血细胞中均未发现这种细菌。通过对性别比例性状遗传的研究证实了这种关联。只有携带这种细胞质细菌的性别比例杂交后代的雌性也表现出性别比例性状，其他雌性在性别比例方面是正常的。对血细胞的透射电子显微镜观察显示，在来自感染品系的血细胞细胞质中存在一种有细胞壁的细菌，具有立克次氏体属成员的特征，而在来自未感染品系的血细胞中则没有。
