title: Interspecific variation in the microanatomy of cosmetid harvestmen (Arachnida, Opiliones, Laniatores).
abstract: Scanning electron microscopy (SEM) is a useful tool for identifying interspecific variation in often overlooked structures that may represent useful sources for informative phylogenetic characters. In this study, we used SEM to compare the morphology of 12 cosmetid species from Central America, the Caribbean, and North America including multiple species for the genera Cynorta, Erginulus, and Paecilaema. To determine if microanatomical structures were unique to the cosmetid taxa under examination, we investigated the microanatomical structures of six additional species of gonyleptoidean harvestmen representing the families Agoristenidae, Cranaidae, Gonyleptidae, Manaosbiidae, and Stygnidae. Our results indicate that the shape of the ocularium (narrow, intermediate, or broad) did not vary within cosmetid genera, whereas the morphology of the rough pit glands on the eye mound varied considerably between species. Each cosmetid species had 10-20 rough pit glands on the ocularium whereas only the eye mounds of Avima intermedia (Agoristenidae) and Glysterus sp. (Gonyleptidae) had similar structures. With regards to the surface texture of the dorsal scutum, cosmetid harvestmen exhibited a rivulose-microgranulate morphology (6 species), a microtuberculate-rivulose-microrgranulate morphology (4 species), or a microgranulate morphology (2 species). In contrast, each of the gonyleptoidean species exhibited a microgranulate pattern, with the exception of Stygnoplus clavotibialis, which had a rivulose-microgranulate surface texture. For cosmetid harvestmen, we observed considerable interspecific variation in the shape and number of teeth on the fixed and moveable fingers of the male chelicerae. Similarly, we also observed interspecific variation in the distribution and shape of tubercles on the ventral and dorsal surfaces of the femur of the pedipalp. Overall, our results indicate that there are several microanatomical structures associated with the ocularium, dorsal scutum, male chelicera, and pedipalp that could represent informative phylogenetic characters in future taxonomic studies of cosmetid harvestmen.
authors.affiliation: Department of Biology, Virginia Wesleyan College, 1584 Wesleyan Drive, Norfolk, Virginia, 23502.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Rodriguez
authors.forename: Victor R
authors.initials: VR
authors.lastname: Townsend
authors.forename: Megan B
authors.initials: MB
authors.lastname: Johnson
authors.forename: Tara B
authors.initials: TB
authors.lastname: White
mesh_terms: D000818:Animals; D001097:Arachnida / Q000145:classification / Q000648:ultrastructure*; D001531:Belize; D003364:Costa Rica; D005260:Female; D008297:Male; D008800:Mexico; D008855:Microscopy, Electron, Scanning; D010802:Phylogeny; D013045:Species Specificity; D014300:Trinidad and Tobago; D014481:United States
keywords: cuticle; gonyleptoidea; ocularium; pedipalp; rough pit glands