Predator recognition and anti-predatory behaviour in a recent aquatic invader, the killer shrimp (Dikerogammarus villosus)

Matteo Rolla,Carlos De Leaniz,Sofia Consuegra

doi:10.3391/ai.2020.15.3.08

Abstract

Abstract The killer shrimp (Dikerogammarus villosus) is one of the most recent, but also most damaging, aquatic invasive species in Europe, but information on how the species responds to novel predation pressures in recently invaded areas is very limited. We employed an open test arena to examine predator recognition and anti-predatory behaviour in killer shrimp exposed to either blank water or water conditioned with fish kairomones to simulate a predator threat. Within five years after their introduction, killer shrimp spent much more time hiding in the presence of fish kairomones than when they were exposed to blank water. However, no significant difference was found in aggregation behaviour, and killer shrimp were strongly attracted to the scent of conspecifics regardless of predator threat. Given the strong selective pressures that fish predators can exert on native and invasive gammarids, our findings highlight the need to consider prey-predator interactions to better predict the dispersal and likely impact of killer shrimp into invaded ecosystems.

Highlights

IntroductionFrom a prey-predator perspective two opposing selective forces may confront invasive species when they colonise a new area: the absence of former predators may facilitate their establishment (the enemy release hypotheses – Colautti et al 2004), while their different appearance (the oddity effect – Almany et al 2007) and lack of co-evolutionary history (the “naïve prey” hypothesis – Sih et al 2010) may curtail it
From a prey-predator perspective two opposing selective forces may confront invasive species when they colonise a new area: the absence of former predators may facilitate their establishment, while their different appearance and lack of co-evolutionary history may curtail it
We examined the attraction of single killer shrimp to the scent of conspecifics in an open-test arena scented with stickleback kairomones or with blank water

Summary

Introduction

From a prey-predator perspective two opposing selective forces may confront invasive species when they colonise a new area: the absence of former predators may facilitate their establishment (the enemy release hypotheses – Colautti et al 2004), while their different appearance (the oddity effect – Almany et al 2007) and lack of co-evolutionary history (the “naïve prey” hypothesis – Sih et al 2010) may curtail it. Whether invasive species thrive or flounder may depend on what predators they encounter, and how they respond to them. This may result in “boom and bust” cycles, reflecting prey-predator dynamics (Strayer et al 2017). Very little is known about anti-predatory strategies of invasive species in novel habitats. The killer shrimp (Dikerogammarus villosus) is a freshwater gammarid indigenous to the Ponto-Caspian region which has recently invaded Western Europe (Tricarico et al 2010), and which constitutes a good system to examine anti-predatory strategies in novel habitats. The species has a large size for a gammarid (1.8–30 mm; Aldridge 2015), a

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