The Nutritional Content of Prey Affects the Foraging of a Generalist Arthropod Predator

Abstract

While foraging theory predicts that predatory responses should be determined by the energy content and size of prey, it is becoming increasingly clear that carnivores regulate their intake of specific nutrients. We tested the hypothesis that prey nutrient composition and predator nutritional history affects foraging intensity, consumption, and prey selection by the wolf spider, Pardosa milvina. By altering the rearing environment for fruit flies, Drosophila melanogaster, we produced high quality flies containing more nitrogen and protein and less lipid than low quality fruit flies. In one experiment, we quantified the proportion of flies taken and consumption across a range of densities of either high or low quality flies and, in a second experiment, we determined the prey capture and consumption of spiders that had been maintained on contrasting diets prior to testing. In both cases, the proportion of prey captured declined with increasing prey density, which characterizes the Type II functional response that is typical of wolf spiders. Spiders with similar nutritional histories killed similar numbers of each prey type but consumed more of the low quality prey. Spiders provided high quality prey in the weeks prior to testing killed more prey than those on the low quality diet but there was no effect of prior diet on consumption. In the third experiment, spiders were maintained on contrasting diets for three weeks and then allowed to select from a mixture of high and low quality prey. Interestingly, feeding history affected prey preferences: spiders that had been on a low quality diet showed no preference but those on the high quality diet selected high quality flies from the mixture. Our results suggest that, even when prey size and species identity are controlled, the nutritional experience of the predator as well as the specific content of the prey shapes predator-prey interactions.

Interactions among morphotype, nutrition, and temperature impact fitness of an invasive fly

“…The contents of sugar, glycogen, and lipids on female flies were determined using a hot anthrone and vanillin assay, following a previous protocol (Tochen et al, ) adapted for 96‐well microplates (Wong, Cave et al, ). Protein content was measured using the Bradford assay (Jones, Hare, & Compton, ), previously adapted for Drosophila (Schmidt, Sebastian, Wilder, & Rypstra, ). A calibration standard was made by performing a Bradford assay on concentrations of 73, 80.3, 87.6, 94.9, 102.2, and 109.5 µg/ml of bovine gamma globulin (1.46 mg/ml; #500‐001 Bio‐Rad, Hercules CA, USA).…”

“…The contents of sugar, glycogen, and lipids on female flies were determined using a hot anthrone and vanillin assay, following a previous protocol (Tochen et al, 2016) adapted for 96-well microplates (Wong, Cave et al, 2018). Protein content was measured using the Bradford assay (Jones, Hare, & Compton, 1989), previously adapted for Drosophila (Schmidt, Sebastian, Wilder, & Rypstra, 2012 A general linear model (GLM) was performed using diet (P:C ratio) as a fixed effect and nutrient content as an outcome variable. This was done individually for each nutrient (protein, sugar, glycogen, and lipids) and each fly morph.…”

Assessing changes in arthropod predator–prey interactions through DNA‐based gut content analysis—variable environment, stable diet

“…Adult Diptera are prey of relative high nutritional value and do not show anti-predator behaviour besides flight (Rickers, Langel, & Scheu, 2006). Indeed, wolf spider will select for such prey in order to maximize energy uptake for metabolic and catabolic expenditures, such as reproduction (e.g., Schmidt, Sebastian, Wilder, & Rypstra, 2012). Interestingly, however, the high local abundance of specific Diptera, like muscid and tachinid flies (Figure 3; see also Loboda et al, 2018;Tiusanen, Hebert, Schmidt, & Roslin, 2016;Wirta, Vesterinen, et al, 2015), is not reflected in the gut content.…”

Caught in the web: Spider web architecture affects prey specialization and spider–prey stoichiometric relationships

“…These differences in the architecture of the webs may result in different types of prey being captured (Blamires, 2010; Guevara & Avilés, 2009; Sanders et al., 2015). Although the nutritional content of captured prey is beyond the control of the spider (Mayntz, Raubenheimer, Salomon, Toft, & Simpson, 2005), web architecture likely affects the energy pathways and the stoichiometry of spider–prey interactions via selective capture and feeding (Mayntz, Toft, & Vollrath, 2009; Schmidt et al., 2012). …”