Cold induced changes in lipid, protein and carbohydrate levels in the tropical insect Gromphadorhina coquereliana.

Insects cope with thermal stressors using mechanisms such as rapid cold hardening and acclimation. These mechanisms have been studied in temperate insects, but little is known about their use by tropical insects in response to cold stress. Here, we investigated whether cold stress (1×8 h and 3×8 h at 4°C) triggers a metabolic response in the Madagascar cockroach Gromphadorhina coquereliana. We examined the effects of cold on the levels of selected metabolites in the fat body tissue of G. coquereliana. After cold exposure, we found that the quantity of total protein increased significantly in the insect fat body, whereas glycogen decreased slightly. Using antibodies, we observed upregulation of AQP-like proteins and changes in the HSP70 levels in the fat body of G. coquereliana when exposed to cold. We also examined the content and nature of the free sugars in the G. coquereliana hemolymph and discovered an increase in the levels of polyols and glucose in response to cold stress. These results suggest an important role of the fat body tissue of tropical insects upon cold exposure.