The effect of changing juvenile nutritional conditions and compensatory growth on life history traits in a field cricket, Gryllus texensis

An organism's juvenile environment can significantly impact its adult phenotype. If an individual grows up in a resource-poor environment but the resource conditions improve, the organism can compensate for its reduced development. Although compensation is beneficial, the fast growth rate associated with it can be costly. To test for evidence of compensatory growth and its costs on adult traits, immunity, and reproduction in insects, I raised Gyllus texensis field crickets on either a good- or poor-quality diet, switched their diets half way through their juvenile period, and compared their growth rates. The poor-good quality diet should mimic compensatory growth. Once the crickets matured, I tested for effects of diet treatment on time to maturity, body mass, body size, and body condition. I also determined disease resistance of adult crickets by monitoring their survival after an injection with the bacteria Serratia marcescens. After each cricket died, I measured their reproductive investment to determine any costs associated with improving juvenile nutritional conditions. Even though I did not find any evidence of compensatory growth in my experimental crickets, diet treatment did have an effect on adult life history traits and reproductive investment. Crickets on the improving diet treatment took significantly longer to mature than good-good quality diet crickets, and were lighter, smaller and in poorer body condition than the crickets on the good-good quality diet. Despite negative effects of an improving juvenile diet on adult traits, there was no effect on reproductive investment or disease resistance. Lack of reproductive and immunity differences between the good-good quality and poor-good quality diet crickets suggests that they were able to compensate for their period of poor nutrition through increasing investment in reproduction and immunity over body size and body condition. My results imply that crickets might be more resilient to fluctuations in resource conditions than organisms in other taxa.