Meeting Abstract
As in mammals, most arachnid fertilization occurs internally, allowing for a variety of post-copulatory mechanisms to take place. Females are expected to exert some level of control over sperm fate when 1) the the point of fertilization is particularly distant from the point of oogenesis, 2) the time of fertilization is occurs significantly later than the time of mating, 3) sperm are non-motile, and/or 4) the morphology of females allows for selective containment of sperm. Many of these conditions are met in Opiliones. Fluorescent microscopy of spermathecae from Opiliones of the suborder Eupnoi has revealed a variety of morphologies that may have critical function in controlling seminal movement, and we have evidence of polygynandrous mating and delayed oviposition in a number of species. Preliminary data on spermathecal morphology in temperate genera Hadrobunus and Leiobunum has deviated from initial expectations that more complex spermatheca would be found in species with conflict-based mating systems, as females of some species with high sexual antagonism have relatively simplistic spermatheca, while females of some species with low antagonism have multi-chambered organs with apparent valvular openings. These findings will have significant implications for the study of reproductive mode maintenance in facultatively parthenogenetic species that may use spermathecal mechanisms to withhold or bias paternity.
