How Lepidopteran Larval Spiracles are Really Made: The Lamellae
The external lamellae of larval spiracles are often easily noticed by eye or a stereo microscope. Despite their importance, the larval spiracle lamellar structure has been inadequately studied and described. Lamellae largely are considered to be fingerlike projections and in most cases lamellae are imaged with one or two surface Scanning Electron (SEM) micrographs. Larval lamellae in different species range from simple lamellae that can be described from two-dimensional micrographs, to in most cases lamellar carpets that must be imaged from three-dimensional anaglyphs or stereo pairs in order to correctly ascertain their structure and the differences between species. We find it necessary to image most larval spiracles with many stereo pairs taken from different angles of view. It is also necessary to make transverse cuts of the spiracles to see the true three-dimensional structure of the lamellae and to view the interior of the spiracles. In large species we also dissect the specimen so as to view the entire spiracle from the interior. Lamellar plates linked together to form lamellar carpets show an economy of structure so that air filtration tubercles, projections, or filaments are arranged only on the dorsum and laterally on the carpet that faces the other side. We will present images from over a dozen species, many through stereo anaglyphs, and some species will include first as well as mature and final instars. Many images are from live larvae imaged directly in a variable pressure SEM.
Caste-Bias in Odorant-Binding Protein Genes of the Polyembryonic Wasp Copidosoma floridanum
A single egg from the polyembryonic wasp Copidosoma floridanum produces soldier and reproductive larvae during development within its caterpillar host. The expression patterns of 8 Copidosoma odorant-binding protein (OBP) genes were investigated for caste-bias using both reverse transcription-polymerase chain reaction (RT-PCR) and in situ expression studies. Six of the 8 genes are clearly biased in their expression towards one or the other larval caste. Three distinct in situ probe hybridization patterns were observed for the OBP genes, none in tissues with a known chemosensory function. Two of the expression patterns suggest the majority of the OBP genes come into contact with hemolymph of the host caterpillar. One of these expression patterns was uniquely associated with the extra-embryonic membrane encompassing each of the reproductive larvae. The absence of OBP gene expression in the membrane surrounding soldier larvae suggests many of the genes characterized in this study are performing caste-specific functions in the host.
20 • Stephanie R. Balser, Jennifer A. Zettler, Bil Leidersdorf
Preference of Insect Frass in Fungus Gardening Cyphomyrmex Ants
The Cyphomyrmex genus of fungus-growing ants is a little known group related to the better-known leafcutter ants of the genus Atta. Unlike the leafcutters, Cyphomyrmex ants use herbivorous insect excrement, or frass, rather than leaves, as a substrate for their fungal gardens. Given the transient nature of herbivorous insects such as caterpillars (Order Lepidoptera), we wanted to determine whether Cyphomyrmex ants are generalists or exhibit a preference for substrate used for the growth of fungi. In preliminary tests, colonies of Cyphomyrmex rimosus from Chatham County GA were collected and housed in artificial nest chambers consisting of a series of Petri dishes connected by tubing. Ant colonies were allowed free access to test arenas with frass from six different families of Lepidoptera that were reared on five different types of host plants. We assessed ant preference by quantifying the respective amounts of frass removed from arenas. We found that Cyphomyrmex showed a preference for frass based on its size and host plant upon which caterpillars fed.
Dept of Biology, Armstrong Atlantic State University, Savannah, GA
21 • Justin C. Strickland1, Ana P. Pinheiro1, Kristen K. Cecala2, Micahel E. Dorcas1
Physiological Constraints to Respond to Climate Change: Insights From the Effects of Temperature on Standard Metabolic Rate in Larval Salamanders
Predictions of climate change susceptibility are critical in forming conservation policy, however, these predictions cannot be generalized even among sister taxa. As such, the development of species-specific, quantitative predictors of sensitivity to thermal increases is vital to the proper allocation of conservation resources and priorities. Climatic variability hypotheses propose that species occupying larger geographic ranges should develop more robust physiological tolerances and be more resistant to temperature changes. In this study, we investigated the effects of temperature variation on standard metabolic rates (SMR) of two species of larval salamanders, Eurycea cirrigera and Eurycea wilderae, that share similar life histories but occupy distinct range sizes. Specifically, SMR was determined using volume of oxygen consumption during closed-circuit respirometery trials conducted at 5 °C increments between 5 and 25 °C. Standard metabolic rates were influenced by temperature, with a range of temperature-independent SMRs observed at those temperatures above each species’ laboratory-determined thermal preference. Concordant with their thermal preference (15.70 °C) and more narrow geographic range, E. wilderae exhibited a smaller scope of temperatures at which SMR was temperature-dependent relative to E. cirrigera and showed depressed metabolic rates at the highest temperature tested. Our results provide a mechanistic link for an ecological predictor of climate change susceptibility (i.e., range size) and indicate that physiological specialization that occurs in species of narrow geographic ranges may preclude adaptations to climate change.
1 Dept of Biology, Davidson College, Davidson, NC; 2 Dept of Biology, Sewanee: University of the South, Sewanee, TN
22 • John J. Hains, Jessica Logan, Brittany Broome, Sarah Fishburne, Lauren Frees, Rebecca Helstern, Joshua Howard, Garrett Woollen
