Meeting Abstract
Temperature influences many aspects of insect physiology, impacting behavior and survival. Recently, we found that insect hemolymph viscosity is also temperature dependent, showing a 6.4x change from 0 to 45°C in Manduca sexta larvae. As poikilotherms, insects experience a wide range of internal temperatures, suggesting that their circulatory system must accommodate a broad range of viscosities. Changes in hemolymph viscosity could significantly affect the dynamics of circulatory flows. Insects respond physiologically to acclimation at different temperatures with mechanisms such as release of proteins or fatty acids, thereby affecting hemolymph composition, but it is unclear if they also affect viscosity. Here we ask, does rearing temperature affect the viscosity of insect hemolymph? We measured viscosity of hemolymph from Manduca sexta larvae reared in three different temperature regimes: 10/15 (cool), 20/25, (room) and 30/35 (warm) °C, with 10/14 hour night/day cycles. A cone-and-plate viscometer attached to a circulating bath measured viscosity at 5, 15, 25, and 35°C. Cell diameter, volume, viability, and circularity of hemolymph was measured via a ViCell cell counter. Viscosity values were equivalent for all rearing conditions when measured at 25 and 35°C, but hemolymph viscosity decreased for warm and cool-reared insects at 15°C and for cool-reared insects at 5°C. In addition, while there are no differences in cell volume between rearing conditions, average cell diameter was significantly higher in cold-reared insects. These data suggest that compositional changes of hemolymph in response to temperature may also affect viscosity in insects. Supported by NSF 1558052.
