High-lipid prey reduce juvenile survivorship and delay egg-laying in a small linyphiid spider Hylyphantes graminicola

Prey proteins and lipids greatly impact predator life-history traits. However, life-history plasticity offers predators the opportunity to tune the life-history traits in response to the limited macronutrients to allocate among traits. A fast-growing predator species with a strict maturation time may be prone to nutritionally imbalanced prey. Here we tested this hypothesis by examining the effect of the protein-to-lipid ratio in prey on a small sheetweb spider, Hylyphantes graminicola, with a short life-span, using adult Drosophila melanogaster as the prey. By manipulating the macronutrient content of prey to generate three prey types with different protein-to-lipid ratios (i.e., high, intermediate and low), we demonstrated that the majority of the spiders that consumed only these flies could reach full maturity. However, juvenile spiders that consumed high-lipid (low protein-to-lipid ratio) flies had a higher rate of mortality than those consuming medium-protein and high-protein flies. The prey protein-to-lipid ratio had no significant effects on the developmental duration and size at maturity. Although the prey protein-to-lipid ratio had no significant influence on mating behaviour and female fecundity, females reared on high-lipid flies exhibited a significant delay in oviposition compared to those reared on high-protein flies. We conclude that high-lipid prey has negative effects on the survival and reproductive function of H. graminicola. Our study thus provides clear evidence that low plasticity with fast development to a certain size means high nutritional requirement for protein at a cost of lower survival and prolonged time to egg laying when prey have low protein-to-lipid content in H. graminicola.