The evolutionary transformation from muscular to hydraulic movements in spider genitalia: A study based on histological serial sections

许多“高等”蜘蛛的雄性生殖器是复杂和复杂的结构，在插入之前和期间执行各种类型的运动(旋转、倾斜、扭转)。最特别的特征之一是，这些运动不是由肌肉影响的，而是由液压作用的，导致膜(血肿)以一种由折叠模式本身决定的方式展开。然而，在“原始”蜘蛛中，运动是由一对肌肉引起的，这些肌肉被认为与行走腿中移动爪子的肌肉是同源的。一项初步研究表明，特征的分布和特征状态都不是那么简单：某些网眼蜘蛛也会出现肌肉，而不是两种特征状态(肌肉对水力学)，而是最多五种，肌肉的数量和附着位置有很大的差异。这项研究旨在对蜘蛛生殖器形态的这一方面进行全面的处理，以此为基础理解蜘蛛如何以及为什么放弃肌肉，转而进化成液压运动。

The male genitalia of many "higher" spiders (Entelegynae) are intricate and complex structures that perform various types of movements (rotation, tilt, twist) before and during intromission. One of the most extraordinary features is that these movements are not effected by muscles but by hydraulic pressure causing membranes (hematodochae) to unfold in a way determined by the folding pattern itself. In "primitive" spiders, however, movements are caused by a pair of muscles that are thought to be homologous to the muscles that move the claws in walking legs. A preliminary study has shown that neither the distribution of characters nor the character states are that simple: muscles occur also in certain entelegyne spiders, and instead of two character states (pair of muscles versus hydraulics), there are up to five, with substantial variation in the number and attachment sites of muscles. This study aims at a comprehensive treatment of this aspect of spider genital morphology as a basis for an unterstanding of how and why spiders have given up on musles and evolved hydraulic movement instead.