Effects of Nutrition on Developmental Plasticity of Growth in Wing-Dimorphic Crickets

Given its impact on fitness, variation in animal body size has long been a source of interest for biologists . Body size and other important related traits, such as developmental rate and survival, may be determined by the developmental environment (a.k.a., developmental plasticity). Thus, we determined the effects of diet treatment (low- vs. high-density of calories) on the survival, growth, developmental rate, and overall body condition of two types (morphs) of sand field cricket (Gryllus firmus)—shortwinged morphs invest in reproduction at the expense of flight capacity, and long-winged morphs invest in flight capacity at the expense of reproduction. Crickets of each treatment group were reared on a diet of either low-density (10% cat food and 90% bran) or high-density (90% cat food and 10% bran) throughout their entire development. At adulthood, aspects of growth were observed by measuring head width, femur length, and body mass. Contrary to our expectations, crickets reared on the high-density diet took approximately 20% longer to develop—potentially because crickets may not have evolved the ability to safely and efficiently process large amounts of protein found in the high-density diet. Wing morphology also influenced developmental rate where longwinged crickets developed slower, which suggests investment into flight musculature may constrain developmental rate. Overall, females were larger, heavier, and in better body condition while males had wider heads, which aligns with theories of sexual dimorphism—larger females can lay more eggs while males with larger heads (and, thus, larger mouthparts) can win more fights with other males to increase their mating success. In the future, we will examine how these factors (diet, wing morphology, and sex) influence investment into other important traits (e.g., immune function and reproductive effort) to gain insight into the developmental plasticity of traits and trait-trait interactions