Willemart Rodrigo H, Osses Francini, Chelini Marie Claire, Macías-Ordóñez Rogelio, Machado Glauco
Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, São Paulo, SP, Brazil.
Behav Processes. 2009 Jan;80(1):51-9. doi: 10.1016/j.beproc.2008.09.006. Epub 2008 Sep 26.
The evolution of sexually dimorphic traits has been the focus of much theoretical work, but empirical approaches to this topic have not been equally prolific. Males of the neotropical family Gonyleptidae usually present a strong fourth pair of legs armed with spines, but their functional significance is unknown. We investigated the putative functions of the leg armature in the harvestman Neosadocus maximus. Being a non-visual species, the spines on male legs can only be perceived by females through physical contact. Thus, we could expect females to touch the armature on the legs of their mates if they were to evaluate it. However, we found no support for this hypothesis. We did show that (1) leg armature is used as a weapon in contests between males and (2) spines and associated sensilla are sexually dimorphic structures involved in "nipping behavior", during which a winner emerged in most fights. Finally, we demonstrate that five body structures directly involved in male-male fights show positive allometry in males, presenting slopes higher than 1, whereas the same structures show either no or negative allometry in the case of females. In conclusion, leg armature in male harvestmen is clearly used as a device in intrasexual contests.
两性异形性状的进化一直是许多理论研究的焦点，但针对这一主题的实证研究方法却没有那么丰富。新热带区的瘤足蛛科雄性通常具有粗壮且带刺的第四对步足，但其功能意义尚不清楚。我们研究了收获蛛Neosadocus maximus步足武装结构的假定功能。作为一种非视觉物种，雄性步足上的刺只有通过身体接触才能被雌性感知。因此，如果雌性要评估雄性步足上的刺，我们可以预期它们会触摸配偶步足上的武装结构。然而，我们没有找到支持这一假设的证据。我们确实发现：（1）步足武装结构在雄性之间的争斗中被用作武器；（2）刺和相关的感觉器是参与“夹捏行为”的两性异形结构，在大多数争斗中会有一个胜者出现。最后，我们证明，直接参与雄性间争斗的五个身体结构在雄性中呈现正异速生长，斜率大于1，而在雌性中，相同的结构要么没有异速生长，要么呈现负异速生长。总之，雄性收获蛛的步足武装结构显然是用于同性争斗的一种工具。
