Student Research Projects

Ovipositor Morphology of Cosmetid (Arachnida, Opilliones, Laniatores): A New Source of Informative Characters

Student Eric Walker '14
Faculty Mentor(s)
Department Biology
Course BIO 489: Research in Natural Sciences


The external morphology of the penis is an important source of systematic characters in phylogenetic studies of harvestmen. In addition, modern taxonomic studies frequently feature micrographs generated by scanning electron microscopy (SEM) that effectively illustrate penis morphology. In contrast, the external morphology of the ovipositor has largely been ignored, especially for harvestmen belonging to the suborder Laniatores. Comparative studies of ovipositor microanatomy using SEM are generally lacking for species belonging to the Gonyleptoidea, the largest superfamily of laniatorean harvestmen. In an effort to determine if the ovipositor could be a useful source of informative characters for these harvestmen, we investigated interspecific variation in the external morphology of the ovipositor for 14 species belonging to the family Cosmetidae. Our SEM-based study revealed that the external surfaces of the distal tips of the ovipositors of most species were generally divided into four symmetrical lobes, although we observed a bilobed condition in Erginulus clavotibialis and E. subserialis. The distal surfaces were also generally smooth, with the exception of the ovipositor of E. weyerensis, which featured an abundance of small trichomes. We also observed considerable variation in the morphology of the peripheral setae on the distal tip, especially with respect to relative size, the morphology of the shaft, and the number, symmetry and shapes of the distal tips. The functional significance, if any, of variation in the structure of the peripheral setae is unclear. Additional behavioral studies of copulation and oviposition are needed to determine the functional relationships between reproductive morphology and behavior. The considerable interspecific variation that we observed suggests that future comparative studies of cosmetid harvestmen, and perhaps other gonyleptoidean taxa, would benefit from the inclusion of descriptions of ovipositor morphology. I am requesting funds to allow me to travel to, attend, and present at the annual ASB conference in South Carolina.


Association of Southeastern Biologists, Spartanburg, South Carolina, April 2014