Meeting Abstract
Flatworms of the Order Kalyptorhynchia are unusual in that the anterior proboscis, used in prey capture, is separate from the mouth opening. In four families and one genus, the proboscis is always armed with hooks or small teeth. The presence/absence of proboscis armature has been used for classification, uniting the diverse Gnathorhynchidae and defining the monotypic Aculeorhynchidae in the suborder Eukalyptorhynchia, and, within the suborder Schizorhynchia, defining the Karkinorhynchidae, Diascorhynchidae, and Nematorhynchidae and defining the genus Carcharodorynchus within the family Schizorhynchidae. Previous electron-microscopic studies are consonant with the independent evolution of armed proboscides in the two kalyptorhynch suborders, showing that the proboscis armature is derived from intracellular specializations (Gnathorhynchidae) or from the basal lamina (Karkinorhynchidae, Diascorhynchidae, Carcharodorhynchus). Furthermore, analysis of the light-microscopic morphology of the proboscides in the suborder Schizorhynchia suggested that the unarmed proboscis was primitive and the armed proboscides, derived. However, recent molecular phylogenies do not support this simple view, placing the karkinorhynchid suborder Cheliplaninae (possessing an armed proboscis) as the primitive sister group to the remaining Schizorhynchia, and further suggesting that the armed proboscis may have evolved from the unarmed condition multiple times within the remaining Schizorhynchia. Using comparative studies of the proboscis, body-wall musculature, and copulatory organ, I provide a new hypothesis concerning the evolution of the proboscis in the Schizorhynchia. Funding: Winthrop University Research Council and SC INBRE [National Center for Research Resources (5 P20 RR016461) & the National Institute of General Medical Sciences (8 P20 GM103499) from the NIH
