Meeting Abstract
The arthropod exoskeleton provides structure and protection. Exoskeleton mass varies widely both within and between insect taxonomic groups. Further, the exoskeleton can be rigid and largely indigestible for predators. Potential consequences of insect prey exoskeleton for predators include increased handling time, greater digestive metabolism cost, and reduced nutrient assimilation. But, the consequences of feeding on chitinous prey could vary with predator foraging and consumptive modes. We tested the consequences of prey exoskeleton content for nutrient assimilation and digestive bioenergetics of two spiders that differ in feeding mode: a wolf spider (masticator) and black widow (piercer). We predicted lower assimilation and higher digestive costs when feeding on the more chitinous beetles compared to mealworm larvae. We found that less elements (C and N), macronutrients (lipid and protein), and energy were extracted from highly chitinous prey. In particular, black widows deposited adult beetle carcasses with greater protein and energetic content than mealworm carcasses. Although handling time and digestive metabolism (Specific Dynamic Action) did not differ, spiders allocated a greater proportion of prey energy (SDA coefficient) in digestion of more chitinous adult beetles. The feeding and digestive consequences we observed suggest that exoskeleton is an attribute that influences foraging benefits and resource allocation by predators. The digestive modes of predators additionally contributed to differences in the extraction of nutrients from chitinous prey. Future study should further explore the mechanisms by which predator resource intake and deposition from prey varying in exoskeleton content, integrating multiple resource perspectives, contributes to broader ecosystem resource flow.
