Meeting Abstract
The insect circulatory system is responsible for the circulation of nutrients, hormones, and metabolic waste via the transport of hemolymph. The hemolymph also functions to close off wound sites, destroy internal parasites, and, in some cases, aid in thermoregulation. As ectotherms, insects are significantly affected by environmental temperatures, and have evolved multiple mechanisms to respond to temperature extremes. For example, some insects upregulate heat shock proteins in response to heat to minimize protein denaturation, and some increase glycerol production and purge water in response to cold to minimize ice crystal formation. However, the effect of temperature on the physical properties of hemolymph has not been studied, and changes in viscosity in particular may greatly influence an insect’s ability to circulate hemolymph. Here, we used Manduca sexta larvae to measure the effect of temperature on the viscosity of hemolymph. Measurements were taken from 5-45 oC at 5 oC intervals using a cone and plate viscometer (Brookfield Engineering DV-II+ Pro) and an attached water circulator (Lauda RE206) to regulate temperature. To minimize oxygen-induced clotting, experiments were performed in a sealed glove box flooded with nitrogen gas. Preliminary results reveal that viscosity increased with decreasing temperature, showing an increase in average viscosity from 1.9 to 9.2 cP. This ~4x change is greater than that in water, whose viscosity increases from 0.8 to 1.5 cP in the same temperature range. This dramatic change in viscosity may represent an underappreciated factor in the reduction of activity with decreasing temperature. Supported by NSF 1558052 and 1301037.
