Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202, USA.
J Exp Zool B Mol Dev Evol. 2011 Nov 15;316(7):484-99. doi: 10.1002/jez.b.21424. Epub 2011 Jul 27.
The canonical number of eight photoreceptors and their arrangement in the ommatidia of insect compound eyes is very conserved. However significant variations exist in selective groups, such as the Lepidoptera and Hymenoptera, which independently evolved additional photoreceptors. For this and historical reasons, heterogeneous labeling conventions have been in use for photoreceptor subtypes, despite developmentally and structurally well-defined homologies. Extending earlier efforts, we introduce a universal photoreceptor subtype classification key that relates to the Drosophila numbering system. Its application is demonstrated in major insect orders, with detailed information on the relationship to previous conventions. We then discuss new insights that result from the improved understanding of photoreceptor subtype homologies. This includes evidence of functionally imposed ground rules of differential opsin expression, the underappreciated role of R8 as ancestral color receptor, the causes and consequences of parallel R7 photoreceptor addition in Hymenoptera and Lepidoptera, and the ancestral subfunctionalization of outer photoreceptors cells, which may be only developmentally recapitulated in Drosophila. We conclude with pointing out the need for opsin expression data from a wider range of insect orders.
昆虫复眼的光感受器通常有 8 个，它们在小眼单位中的排列非常保守。然而，在一些选择性群体中存在显著的变化，例如鳞翅目和膜翅目，它们独立进化出了额外的光感受器。由于这些原因和历史原因，尽管在发育和结构上具有明确的同源性，但仍存在用于光感受器亚型的异构标记约定。为了解决这个问题，我们参考果蝇编号系统，引入了一个通用的光感受器亚型分类关键方法。我们在主要的昆虫目类中展示了它的应用，并详细介绍了与以前约定的关系。然后，我们讨论了从改进的光感受器亚型同源性理解中获得的新见解。这包括功能上的差异视蛋白表达的强制性规则的证据，R8 作为原始颜色感受器的作用被低估，膜翅目和鳞翅目 R7 光感受器平行添加的原因和后果，以及外光感受器细胞的祖先亚功能化，这可能在果蝇中仅在发育上被重新产生。最后，我们指出需要更多昆虫目类的视蛋白表达数据。
