Michalik Peter, Uhl Gabriele
Zoologisches Institut und Museum, Allgemeine und Systematische Zoologie, Ernst-Moritz-Arndt-Universität, Greifswald, Germany.
J Morphol. 2011 Jul;272(7):814-32. doi: 10.1002/jmor.10950. Epub 2011 Apr 6.
Reproductive competition among males selects for a broad variety of strategies and traits from mate guarding to nuptial food gifts. Males of many dwarf spider species possess conspicuous secondary cephalic modifications, and the few studies available suggest that these cephalic structures are connected to extensive glandular tissue. Because females were observed to contact the male head structures during mating, these traits may have evolved in the context of sexual selection. We investigated the structure, glandular equipment, and sensory equipment of the cephalic regions of several species of the dwarf spider genus Oedothorax with varying degrees of sexual dimorphism using light and electron microscopy. In one Oedothorax species, there are two male morphs that exhibit a cephalic modification (O. gibbosus gibbosus) or not (O. gibbosus tuberosus). Our study demonstrates that all males investigated produce cephalic secretions, irrespective of the morphology of their cephalic region, however, they may differ in amount of secretion and in cellular organization. In males of O. apicatus, O. gibbosus gibbosus and O. retusus the gland cells are very abundant in the area of a cephalic hump, whereas in the less conspicuous O. agrestis, and O. gibbosus tuberosus the gland cells are restricted to a small area behind the ocular region or include the ocular region as in O. fuscus. The glandular tissue consists of two gland types in O. agrestis, O. fuscus, O. gibbosus tuberosus and O. retusus and of only one type in O. apicatus and O. gibbosus gibbosus. The setae present on the head structure of all species seem to function as mechano- and/or chemoreceptors. The implications of our findings for the evolution of secretory head structures are discussed along with their potential for driving speciation.
雄性之间的生殖竞争催生出了各种各样的策略和特征，从配偶守护到婚飞时的食物馈赠。许多矮蛛种类的雄性都有明显的头部次生形态变化，现有为数不多的研究表明，这些头部结构与广泛的腺体组织有关。由于观察到雌性在交配时会接触雄性的头部结构，这些特征可能是在性选择的背景下进化而来的。我们使用光学显微镜和电子显微镜，研究了矮蛛属（Oedothorax）几种具有不同程度两性异形的物种头部区域的结构、腺体组成和感觉器官。在一种矮蛛（Oedothorax gibbosus）中，有两种雄性形态，一种表现出头部形态变化（O. gibbosus gibbosus），另一种则没有（O. gibbosus tuberosus）。我们的研究表明，所有被研究的雄性都会产生头部分泌物，无论其头部区域的形态如何，不过，它们在分泌物的量和细胞组织上可能存在差异。在尖腹矮蛛（O. apicatus）、驼背矮蛛（O. gibbosus gibbosus）和钝腹矮蛛（O. retusus）的雄性中，腺体细胞在头部隆起区域非常丰富，而在不太明显的荒地矮蛛（O. agrestis）和无瘤矮蛛（O. gibbosus tuberosus）中，腺体细胞仅限于眼区后方的一个小区域，或者像深色矮蛛（O. fuscus）那样包括眼区。在荒地矮蛛、深色矮蛛、无瘤矮蛛和钝腹矮蛛中，腺体组织由两种腺体类型组成，而在尖腹矮蛛和驼背矮蛛中只有一种类型。所有物种头部结构上的刚毛似乎都起到了机械感受器和/或化学感受器的作用。我们讨论了这些发现对分泌性头部结构进化的影响，以及它们推动物种形成的潜力。
