Meeting Abstract
The flatworm clade Schizorhynchia comprises approximately 150 species of predators that use an anterior proboscis to capture prey. Taxonomy in this group has relied heavily on the light-microscopic structure of the proboscis. Recent molecular-phylogenetic studies do not support the current classification. In addition to the proboscis, schizorhynchs possess a rather complex male organ, variously armed with spines or cirri. However, the last comprehensive review of this organ in Schizorhynchia was published in 1956 using only light microscopy. My investigation of the male copulatory organ in several schizorhynch species by confocal-laser-scanning and transmission-electron microscopy reveals common features, including an outer sheath of longitudinal muscles surrounding the copulatory bulb (conflicting, in at least one case, with the description originally published), copulatory “hard parts” comprising an eversible cirrus and/or a tubular extension of the ejaculatory duct, muscular connections between the copulatory bulb and hard parts that appear to be capable of cirrus protrusion during copulation, and an epithelial lining of the ejaculatory duct through which pass neck-like extensions of the prostate glands (a feature that was usually missed in earlier light-microscopic studies). Mapping of these characters onto the existing molecular phylogeny suggests additional candidate taxa for investigation. Supported by funds from the Winthrop University Research Council and SC-INBRE (National Center for Research Resources [5 P20 RR016461] and the National Institute of General Medical Sciences [8 P20 GM103499] from the National Institutes of Health).
