Nutritional requirements for web synthesis in the tetragnathid spider Nephila clavipes

Trap-constructing organisms provide a unique opportunity for the study of r esource allocation, because an observer can unambiguously determine the all ocation to foraging. In species that synthesize a trap from physiologically important compounds, there is the further advantage that there may be dire ct tradeoffs between allocation of resources to foraging and physiological functions. We examined the ability of the spider Nephila clavipes (L.; Aran eae: Tetragnathidae) to synthesize resources that are known to be used for both web synthesis and non-foraging physiological functions. We found that choline, required for both web function and physiological function, is an e ssential nutrient: it is not synthesized by this spider. Under laboratory c onditions with a diet of fruit flies, choline is limiting, and the spiders make allocation trade-offs between investing choline in foraging (the web) or in their body.