Micronutrient consumption by female Argiope bruennichi affects offspring survival.

Sexual cannibalism has long been hypothesized to be a foraging decision in which females consume males for the nutrients in their bodies. While few studies have documented fecundity benefits of sexual cannibalism, several recent studies have documented benefits of cannibalism to egg hatching success or offspring survival. We tested if small supplements of dietary essential nutrients fed to female spiders, Argiope bruennichi, would result in increases in offspring survival similar to those seen following sexual cannibalism. All female spiders were prevented from cannibalizing their mates and subsequently fed either: a dead male spider, or a similarly-sized dead fly with one of four nutrient supplements (water control, dietary essential fatty acids, dietary essential amino acids, or nonessential amino and fatty acids). Females that consumed a small supplement of dietary essential amino acids produced offspring that survived simulated overwintering conditions significantly longer than offspring of other treatments. While a previous study found a significant effect of cannibalism on offspring survival using field-collected males as prey, the current study, which used lab-reared males as prey, found no effect of sexual cannibalism on offspring survival. Hence, our results suggest that dietary essential amino acids, which may be sequestered by males from their diet, could be valuable supplements that increase the success of the offspring of cannibalistic females. Further work is needed to determine the source and identity of these dietary essential amino acids and if other essential nutrients (e.g., trace elements, vitamins, etc.) may also be limiting in female diets and affect offspring success.