Meeting Abstract

77.1  Monday, Jan. 6 08:15  Nutrient intake of nymphal and adult Mormon crickets and its effects on immunity SRYGLEY, R.B.*; USDA-Agricultural Research Service robert.srygley@ars.usda.gov

For insects, two of the most important dietary macronutrients are carbohydrates and protein, and many organisms regulate dietary intake of both. In the field, carbohydrate (C) to protein (P) intake of Mormon crickets is indicative of nutritional imbalance that had major effects on immunity to pathogens. Here we used a set of dietary choice experiments in the lab to investigate the preferences of Mormon cricket nymphs and adults for C and P. Diet pairs were selected that would allow Mormon crickets to reach a single intake target of C:P from four unique starting points. After the last pair of diets was removed on day 7, we assayed phenoloxidase and anti-bacterial activity. Both males and females at both the adult and nymphal stages showed a strong preference for the diet that was richest in macronutrients with equal preference for C or P. When given a choice of a high carbohydrate diet and a high protein diet, the Mormon crickets selected both at random, balancing their daily intake of C and P. Weight gained was highly dependent on the mass of protein consumed, with a conversion factor greater than four times that of the carbohydrates consumed. Those Mormon cricket nymphs that consumed more protein had higher titers of total phenoloxidase, but there was not a significant effect of diet on other measures of immunity. In nature, omnivores might consume an excess of one of the macronutrients because they can often find the other through active searching of their local habitat. However environmental change and interspecific or intraspecific competition can challenge an organism’s ability to encounter required nutrients on a local scale, which contributes to the Mormon crickets’ migratory behaviors. A preference for the richest diet suggests that only the concentration of one macronutrient needs to vary in the environment for Mormon crickets to be highly variable in their nutritional deficiencies.