University of Michigan, Department of Ecology and Evolutionary Biology, Museum of Zoology, 1109 Geddes Ave., Ann Arbor, MI 48109, USA.
Evol Dev. 2011 Jul-Aug;13(4):352-60. doi: 10.1111/j.1525-142X.2011.00490.x.
Some fishes mature and function as one sex and later transform to the other sex in response to social interactions. Previous evidence suggested that a change in developmental timing may be involved in the evolution of adult sex change in fishes. The most recent support for this idea came from reports that sex in the Midas cichlid, Amphilophus citrinellus, was determined by social conditions experienced at the juvenile stage. Differentiation as a male was reported to be dependent on large body size relative to group-mates, and thought to be mediated through aggressive interactions. Here I demonstrate that socially controlled sex determination does not occur as was originally reported. Previously, I found that sex was not associated with body size in juveniles either in nature or in captivity. Similarly, I found no association between aggressive behavior and sex in juveniles. I later demonstrated that socially controlled sex determination does not typically occur in the Midas cichlid and closely related species and supported an alternative mechanism to explain large body size in adult males. Finally, in the current study I analyze gonad histology of fish from the same population used by the original authors and lay to rest the idea of socially controlled sex determination in this species. Recent observations of socially controlled sex determination in juveniles of species that typically change sex at the adult stage are examples of phenotypic plasticity, not genetic variation. Therefore, juvenile socially controlled sex determination does not support a theory that a change in developmental timing is involved in the evolution of adult sex change in fishes.
有些鱼类在成熟和作为一种性别发挥功能后，会根据社会互动转而变成另一种性别。先前的证据表明，发育时间的变化可能与鱼类成年性别转变的进化有关。这一观点最近得到了支持，有报道称，Midas 慈鲷（Amphilophus citrinellus）的性别是由幼年阶段经历的社会条件决定的。据报道，雄性的分化取决于相对于群体的体型大小，并且被认为是通过攻击性的相互作用来介导的。在这里，我证明了之前报道的社会控制性别决定并没有发生。此前，我发现无论是在自然环境还是在圈养环境中，性别的分化与幼鱼的体型大小无关。同样，我也没有发现幼鱼的攻击性行为与性别之间存在关联。后来，我证明了社会控制性别决定在 Midas 慈鲷及其近亲物种中并不常见，并支持了一种替代机制来解释成年雄性的体型大小。最后，在目前的研究中，我分析了来自原始作者使用的同一种群的鱼类的性腺组织学，并彻底否定了该物种存在社会控制性别决定的观点。最近观察到在成年阶段通常会发生性别转变的物种的幼鱼中存在社会控制性别决定，这是表型可塑性的例子，而不是遗传变异。因此，幼鱼的社会控制性别决定并不支持这样一种理论，即发育时间的变化与鱼类成年性别转变的进化有关。
