Dietary routing of nutrients from prey to offspring in a generalist predator: effects of prey quality

1. Reproduction of female wolf spiders (Pardosa lugubris; Lycosidae) fed with prey of different quality was investigated. Spiders were fed either a single diet of Drosophila melanogaster (Diptera, high quality), Heteromurus nitidus (Collembola, high quality) or Folsomia candida (Collembola, toxic), or a mixed diet of D. melanogaster and H. nitidus, and of D. melanogaster and F. candida. 2. Nutrient flow from prey into females and from females into offspring during egg production was investigated tracing carbon and nitrogen stable isotopes with prey being enriched in C-13 and/or N-15. 3. There was no benefit of mixing different high-quality prey on female biomass and performance, contrasting with earlier results obtained with juvenile spiders. 4. Folsomia candida was toxic for P. lugubris: females, even if fed a mixed diet also containing high-quality prey, did not reproduce and finally died; spiders did not acquire aversion against F. candida. 5. Tracing stable isotopes documented the incorporation of C and N from prey into females and their offspring; dietary nutrients were routed almost exclusively into egg production. 6. Stable isotope analysis strongly supported the assumption that F. candida causes post-ingestive physiological effects in spiders by inhibiting the incorporation of nutrients from other prey.