Invaders eating invaders: potential trophic interactions between the amphipod Dikerogammarus villosus and juvenile crayfish Orconectes limosus

摘要

We investigated potential interspecific predation between two invasivecrustacean species, currently widespread and co-occurring in Europeaninland waters: the Ponto-Caspian amphipod Dikerogammarus villosus(Gammaridae) and the North American spiny-cheek crayfish Orconecteslimosus (Cambaridae). We evaluated interactions of adult specimens ofD. villosus and juvenile O. limosus (from the 3rd developmental stage –DS) under conditions with and without feeding. We used two differentexperimental setups: short-term (one-week) rearing in aquaria each containing30 specimens of either single-species or mixed stock, and 20-daylongrearing in small circular plates with one individual of each species.In the aquaria, a significant effect of D. villosus presence on survival ofO. limosus stocks was found, with stronger influence on unfed stocks.Survival of D. villosus was not influenced by either O. limosus presenceor feeding. Direct predation of D. villosus on juvenile O. limosus, predominantlyon the 3rd DS, was often observed in the small plates. The 5th DSO. limosus was killed only a few times and was already able to feed onadult D. villosus. Our results show that both species are able to affecteach other negatively through intra-guild predation: D. villosus may successfullyfeed on juvenile O. limosus (3rd and 4th DS), but larger crayfishcan resist predation by the amphipod.