REYNOLDS, Julie A.; HAND, Steven C.; Louisiana State University; Louisiana State University: Developmental arrest and metabolic downregulation in embryos of the Southern ground cricket, Allomenobius socius.

Diapause is an endogenously controlled state of dormancy that allows organisms to tolerate harsh environmental conditions. It is characterized by developmental arrest and a species-specific suite of physiological changes that include decreased metabolism and increased production of compounds protective against cellular stress. In the Southern ground cricket, Allonemobius socius, mature females reared under short daylengths (14:10, L:D) produce embryos that enter diapause, while females reared under long photoperiods (16:8, L:D) produce embryos that do not enter diapause but rather hatch as nymphs after 15-20 days when incubated at 29 &degC. Morphological assessment of developmental arrest was conducted by chemically clearing the yolk and then viewing the embryo through the chorion with light microscopy. Diapause was confirmed by the failure of limb bud and eye spot development within the expected incubation times as measured for non-diapause embryos. Developmental arrest during diapause in A. socius occurs at the early gastrula stage, approximately 96 h post-oviposition when incubated at 29 &degC. Physiologically, diapause in A. socius is characterized by a modest 50 % decrease in oxygen consumption rates compared to non-diapause embryos of a similar stage. Preliminary data suggest that non-diapausing gastrulae exhibit atypically low adenylate energy charge (AEC) and ATP:ADP ratios compared to pharate first instars. AEC is reduced by about 8 % in diapause gastrulae compared to non-diapause gastrulae, while ATP:ADP ratio is decreased by approximately 15 %. Future studies of differential gene expression will investigate mechanisms controlling developmental arrest during diapause. (Sigma Xi and Orthoptera Society Research Grants to JAR, and DARPA N00173-01-1-G011 to SCH).