Student Research Projects

The microscopic anatomy of the ovipositor of cosmetid harvestmen from the genera Paecilaema and Eupoecilaema

Student Keane Dye '16 (Biology and Chemistry)
Britton Hipple ‘16 (Chemistry)
Marcy Elizabeth Wade '15 (Biology and Hispanic Studies)
Department Biology
Course Biology 400: Scanning Electron Microscopy (SEM)

Abstract

The state of the taxonomy of harvestmen belonging to the family Cosmetidae rests in a poorly resolved state with diagnoses of genera based upon a combination of tarsal segments on leg I and the armature of the dorsal scutum. While male reproductive anatomy (penis) is commonly used to differentiate species in many groups of Laniatorean harvestmen, the morphology of the female reproductive system (ovipositor) has largely been ignored. In this study, we sought to assess variation in the microscopic anatomy of the ovipositor in two genera of the family Cosmetidae. These taxa, Paecilaema and Eupoecilaema, include a large number of species from Central America that have seven tarsomeres on leg I and a variable pattern of tubercles on the dorsal scutum. We used scanning electron microscopy to examine the ovipositors of 14 species of Paecilaema and 3 species of Eupoecilaema. Our results indicate that there is considerable interspecific variation in the ovipositor morphology, especially with respect to the number and shape of distal tips of peripheral setae as well as the surface texture of the setal shaft. Most species had the ovipositors with four distinct external lobes with smooth surface textures (no surface denticles were observed), 10 straight, peripheral setae (3 per anterior lobe and 2 per posterior lobe) that inserted into undivided sockets that were not in direct contact with each other. The only consistent difference between the genera Eupoecilaema and Paecilaema was that all of the observed Eupoecilaema species exhibited the same number and shape of distal tips, a three symmetrical split, while the Paecilaema species shared no common pattern among the shape and number of distal tips exhibited. On the basis of female reproductive anatomy, four species groups were identified consisting of either two or more species that shared morphological characteristics in every category observed. The genera Paecilaema had three species groups, while the genera Eupoecilaema had one. Eupoecilaema jarrellae was a unique species that exhibited a striated shaft, setting it apart from the others in the genera. The Paecillaema species toledense and variegatum, two separate unidentified species from French Guyana, and wallerae all exhibited morphological characteristics of the female