Water warming increases aggression in a tropical fish

Zi Xun Kua,Ian M Hamilton,Jake Gilliland,Allison L Mclaughlin,Elizabeth A Hoskins,Reed M Brodnik,Stuart A Ludsin,S Conor Keitzer

doi:10.1038/s41598-020-76780-1

Abstract

Our understanding of how projected climatic warming will influence the world’s biota remains largely speculative, owing to the many ways in which it can directly and indirectly affect individual phenotypes. Its impact is expected to be especially severe in the tropics, where organisms have evolved in more physically stable conditions relative to temperate ecosystems. Lake Tanganyika (eastern Africa) is one ecosystem experiencing rapid warming, yet our understanding of how its diverse assemblage of endemic species will respond is incomplete. Herein, we conducted a laboratory experiment to assess how anticipated future warming would affect the mirror-elicited aggressive behaviour of Julidochromis ornatus, a common endemic cichlid in Lake Tanganyika. Given linkages that have been established between temperature and individual behaviour in fish and other animals, we hypothesized that water warming would heighten average individual aggression. Our findings support this hypothesis, suggesting the potential for water warming to mediate behavioural phenotypic expression through negative effects associated with individual health (body condition). We ultimately discuss the implications of our findings for efforts aimed at understanding how continued climate warming will affect the ecology of Lake Tanganyika fishes and other tropical ectotherms.

Highlights

Our understanding of how projected climatic warming will influence the world’s biota remains largely speculative, owing to the many ways in which it can directly and indirectly affect individual phenotypes
The main objective of our study was to shed insight into how climate warming might affect the behaviour of tropical freshwater ectotherms such as the endemic Lamprologini cichlid assemblage of Lake Tanganyika
We found that the frequency of aggressive behaviour in the Tanganyikan cichlid Julidochromis ornatus increased after individuals were exposed to the future projected temperature of Lake Tanganyika surface waters at the end of the 21st century (i.e., ~29 ◦C)[56], which happens to be the current-day extreme high temperature[56,61]

Summary

Introduction

Our understanding of how projected climatic warming will influence the world’s biota remains largely speculative, owing to the many ways in which it can directly and indirectly affect individual phenotypes. Changes in the thermal environment are expected to affect the demographics of native populations through direct and indirect influences associated with altered physiology (e.g., metabolism)[23,24]. For aquatic ectotherms such as fish residing in tropical lakes, warming could be problematic for at least two reasons. While species can and have evolved to cope with environmental changes[31,32], rapid warming and other forms of HIREC likely will require alternative means for populations to survive under these kinds of selection pressures

Objectives

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Results

Conclusion