The adaptive value of camouflage and colour change in a polymorphic prawn

Rafael Campos Duarte,Augusto Alberto Valero Flores,Martin Stevens

doi:10.1038/s41598-018-34470-z

Rafael Campos Duarte, Augusto Alberto Valero Flores + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-34470-z

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Abstract

Camouflage has been a textbook example of natural selection and adaptation since the time of the earliest evolutionists. However, aside from correlational evidence and studies using artificial dummy prey, experiments directly showing that better camouflaged prey to predator vision are at reduced risk of attack are lacking. Here, we show that the level of camouflage achieved through colour adjustments towards the appearance of seaweed habitats is adaptive in reducing predation pressure in the prawn Hippolyte obliquimanus. Digital image analysis and visual modelling of a fish predator (seahorse) predicted that brown prawns would be imperfectly concealed against both brown and red seaweed respectively, whereas pink prawns should be well camouflaged only in red weed. Predation trials with captive seahorses (Hippocampus reidi), coupled with high-speed video analyses, closely matched model predictions: predation rates were similar for brown prawns between seaweed types, but pink individuals were attacked significantly less on red than brown weed. Our work provides some of the clearest direct evidence to date that colour polymorphism and colour change provides a clear adaptive advantage for camouflage, and also highlights how this can be asymmetric across morphs and habitats (i.e. dependent on the specific background-morph combination).

Highlights

The study of animal coloration has fascinated evolutionary biologists for centuries and provided important evidence of adaptation and natural selection[1,2]
Colour-changing species make ideal systems to investigate the adaptive value of camouflage[21], because they allow testing the importance of colour adjustments of immigrant individuals upon contact with novel habitat, and whether survival advantages of adjusted individuals are symmetrical between habitats
Considering previous results on habitat-specific prawn camouflage based on general colour reflectance[32], we tested the hypothesis that the survival advantage of camouflage through colour change is dependent on the seaweed habitat, with much reduced detection and predation rates on individuals adjusting their coloration to the red seaweed Galaxaura compared to those shifting towards the brown seaweed Sargassum

Summary

Introduction

The study of animal coloration has fascinated evolutionary biologists for centuries and provided important evidence of adaptation and natural selection[1,2]. Based on their likelihood to remain unnoticed by a seahorse predator, which exhibits colour vision and detects prey primarily using visual cues[31,34], we quantified the camouflage of prawn morphs on both the host and the alternative seaweed habitat using image analyses and visual modelling.

Results

Conclusion