Chemical Cues Released by an Alien Invasive Aquatic Gastropod Drive Its Invasion Success

Jacqueline L Raw,Renzo Perissinotto,Nelson A F Miranda,Brock Fenton

doi:10.1371/journal.pone.0064071

Abstract

BackgroundChemical cues provide aquatic organisms with sensory information that guides behavioural responses and thus interactions among themselves, each other and the environment. Chemical cues are considered important for predator avoidance, foraging, larval settlement and broadcast spawning in aquatic environments. However, the significance of their role as drivers of direct interactions between heterospecifics has been largely overlooked.Methodology/Principal FindingsA video camera and a demarcated arena were used in situ to record behavioural responses of three native gastropod species, Assiminea cf. capensis, Melanoides tuberculata and Coriandria durbanensis, exposed to treatments representing chemical cues released by a non-native invasive gastropod, Tarebia granifera. The responses were measured quantitatively as displacement and orientation of movement at locations in St Lucia Estuary, within the iSimangaliso Wetland Park, a UNESCO World Heritage Site on the east coast of South Africa. All native gastropods exhibited a negative taxis response to chemical cues released by T. granifera, while T. granifera individuals responded randomly to conspecifics. Displacement was measured relative to the source of the extract, the number of steps taken were determined with path analysis and orientation was determined from the mean (±95% CIs) turning angles, with significant negative turning angles representing negative taxis. Responses to treatments corresponding to the environment and conspecifics were random and undirected, indicating kinesis.Conclusion/SignificanceThis study presents evidence for interactions driven by chemical cues between a non-native invasive gastropod and several gastropods native to South Africa. The results indicate that chemical cues can facilitate invasion success as the behavioural response of native gastropods is to move away allowing additional food and space resources to become available to T. granifera.

Highlights

Biological invasions, considered a major component of anthropogenic global change, provide an opportunity to study ecological principles which govern the coexistence of populations within communities [1]
Gastropods and Experiment Sites The behavioural responses of the three native gastropod species, Assiminea cf. capensis, Melanoides tuberculata and Coriandria durbanensis, to chemical cues released by T. granifera were quantified independently in terms of movement and orientation following a protocol adapted from Wollerman et al [25]
This study has not identified, isolated and purified the chemical cue in question through biochemical assays, the significant quantified behavioural responses suggest that the interspecific interaction among Tarebia granifera and native gastropods is driven by chemical cues

Summary

Introduction

Biological invasions, considered a major component of anthropogenic global change, provide an opportunity to study ecological principles which govern the coexistence of populations within communities [1]. Studies of biotic interactions such as predation, competition and facilitation between non-native and native species can translate to a better understanding of the relationships which exist among established native species [2]. Biotic interactions remain an important component of invasion success [2] and are generally investigated at the level of the individual by quantifying behavioural responses [7]. Research has focussed on the interactions between agonistic competitors [8] and novel predator-prey relationships [9] These studies have quantified behavioural responses in terms of activity levels, aggression, dominance and searching for refuge. Chemical communication among organisms was recognized earlyon as an important component influencing behaviour [14,15]. Chemical cues provide aquatic organisms with sensory information that guides behavioural responses and interactions among themselves, each other and the environment. The significance of their role as drivers of direct interactions between heterospecifics has been largely overlooked

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