Diet-based sodium regulation in 6th instar grasshoppers, Schistocerca americana (Drury) (Orthoptera: Acrididae).

This study analyzed sodium intake by Schistocerca americana (Drury) (Orthoptera: Acrididae) grasshoppers using three different seedling wheatgrass based diet treatments to simulate a natural food source. Sodium is a key nutrient for grasshopper cells, nerves, and reproduction. Grasshoppers acquire sodium from plants that they consume. However, it is unclear if grasshoppers self-regulate their sodium intake. Additionally, if grasshoppers self-regulate their sodium intake, the extent to which they do is uncertain. Newly molted 6 th instar grasshoppers were fed one of three diets in which the level of sodium that they had access to was varied. The S. americana grasshoppers consumed significantly less of the 0.5 M added sodium only diet when presented with an option to choose between this diet and a no-sodium-added diet ( t = 9.6026; df = 7; P < 0.0001). Grasshoppers in the 0.5 M added sodium only treatment consumed a significantly lower amount of food ( P < 0.0001) as well as gained a significantly lower average mass ( P < 0.0001) compared to the grasshoppers in the no-sodium-added only treatment. Our results generally correlated with previous studies on Locusta migratoria (L.) (Orthoptera: Acrididae) and information about the ecological tolerances and nutritional requirements of grasshoppers. Our data suggests that S. americana grasshoppers are capable of self-regulating their sodium intake. Additionally, we show that high concentrations of sodium in grasshopper diets have a negative effect on body mass. Our study illustrates that diet-based sodium regulation is a factor in the relationship between insect herbivores and their environments.