02668nas a2200181   4500008004100000245010600041210006900147300001000216490000700226520204700233653002102280653002202301653002202323100002302345700002102368700002502389856007202414       2013                        eng d00aFunctional aspects of genital differences in Leucauge argyra and L. mariana (Araneae: Tetragnathidae)0 aFunctional aspects of genital differences in Leucauge argyra and  a59-690 v413 aMorphological studies have documented the tendency for male genitalia to diverge rapidly compared to other body parts in many animal groups, including spiders. But documentation of how differences in genital structures of closely related species correlate with differences in the behavior of their genitalia during copulation is rare. This study describes how the genitalia of the spider Leucauge argyra (Walckenaer 1841), a species in which both male and female have unusual derived structures, are used during copulation and compares their sexual behavior with previous descriptions of genital behavior in the congener L. mariana (Taczanowski 1881) and the genital morphology of other Leucauge species. Males of L. argyra have two prominent derived genital structures, both of which interact directly with the female; one of them apparently locks against a modified female structure, while the other is inserted into the female atrium. On the other hand, the most prominent derived female structure does not lock against or receive any male structure and may serve to sense movements of the male palp, perhaps to trigger deposition of a strong copulatory plug by the female. The female atrium is unusual in that it receives insertions of both the male’s conductor and his cymbial hook. Both derived male structures of L. argyra may have evolved to stabilize the male’s genitalia during intromission, perhaps in response to violent and dangerous female resistance or to perforate the strong plug that is probably produced or at least moved into place by the female. The rotating and projecting movements executed by male genitalia in L. argyra, which as in other spiders are presumably produced by the hydraulic unfolding of complex membranes in the palp, are quite different from the movements of the male genitalia of L. mariana. We speculate that in spiders in general, changes in palpal sclerites are often accompanied by changes in the movements of the sclerites, and thus by changes in the unstudied internal membranes of the palp.10aCopulatory plugs10agenital evolution10agenital movements1 aBarrantes, Gilbert1 aAisenberg, Anita1 aEberhard, William, G  uhttp://www.americanarachnology.org/JoA_tocs/JOA_contents_v41n1.html