Diet sensitivity in field crickets

Animals adjust resource acquisition throughout life to meet changing
physiological demands of growth, reproduction, activity, and somatic
maintenance. Wing-polymorphic crickets invest in either dispersal or
reproduction during early adulthood, providing a system in which to
determine how variation in physiological demands, determined by sex and
life history strategy, impact nutritional targets, plus the consequences
of nutritionally imbalanced diets across life stages. We hypothesized that
high demands of biosynthesis (especially oogenesis in females) drive
elevated resource acquisition requirements and confer vulnerability to
imbalanced diets. Nutrient targets and allocation into key tissues
associated with life history investments were determined for juvenile and
adult male and female field crickets (Gryllus lineaticeps)  when
given a choice between two calorically equivalent but nutritionally
imbalanced (protein- or carbohydrate-biased) artificial diets, or when
restricted to one imbalanced diet. Flight muscle synthesis drove elevated
general caloric requirements for juveniles investing in dispersal, but
flight muscle quality was robust to imbalanced diets. Testes synthesis was
not costly, and life history investments by males were insensitive to diet
composition. In contrast, costs of ovarian synthesis drove elevated
caloric and protein requirements for adult females. When constrained to a
carbohydrate-biased diet, ovary synthesis was reduced in reproductive
females, eliminating their advantage in early life fecundity over the
dispersal morph. Our findings demonstrate that nutrient acquisition
modulates dispersal-reproduction trade-offs in an age- and sex-specific
manner. Declines in food quality will thus disproportionately affect
specific cohorts, potentially driving demographic shifts and altering
patterns of life history evolution.