Differences in Colour Pattern, Behaviour and Gene Expression in the Brain Suggest Divergent Camouflage Strategies in Sympatric Reef Fish Species

• Published in: Molecular ecology Vol. 34; no. 11; pp. e17748 - n/a
• Main Authors: Heckwolf, M. J., Gismann, J., González‐Santoro, M., Coulmance, F., Fuß, J., McMillan, W. O., Puebla, O.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.06.2025; John Wiley and Sons Inc
• Subjects: Animals; Behavior, Animal; behaviour/social evolution; Biological Mimicry - genetics; Brain; Brain - metabolism; Brain - physiology; Camouflage; Color; Coloration; Coral Reefs; Diencephalon; Divergence; Escape behavior; fish; Fishes - genetics; Fishes - physiology; Gene Expression; gene expression regulation; Hypoplectrus; Immune response; molecular evolution; Neuroplasticity; optic tectum; Original; ORIGINAL ARTICLE; oxygen; Perciformes - genetics; Perciformes - physiology; Pigmentation - genetics; Predation; predator prey interactions; Predators; Predatory Behavior; Reef fish; Speciation; species; Superior colliculus; Sympatric populations; Sympatry; Tectum; Transcriptome; Transcriptomics; transcriptomics; predator prey interactions; molecular evolution; behaviour/social evolution; speciation
• ISSN: 0962-1083; 1365-294X; 1365-294X
• DOI: 10.1111/mec.17748

ABSTRACT Camouflage is a critical survival strategy that helps to evade predation and increase hunting success. Background matching and disruptive colouration are different camouflage strategies that are subject to different selective pressures and can drive divergence in their associated traits such as colour pattern and behaviour. This study tested whether two closely related reef fish species (Hypoplectrus spp.) with distinct colour patterns exhibit different predator escape responses and differential gene expression in the brain indicative of divergent camouflage strategies. Combining field and laboratory experiments, we show that barred hamlets, characterised by disruptive colouration, are dynamic in their escape responses, while black hamlets, with their darker colouration, had a preference for hiding. The behavioural differences between these species seem to be limited to divergent predator escape responses since other behaviours such as activity or sociability did not differ. Importantly, the observed behavioural differences were accompanied by transcriptomic differences in their brains, particularly in regions associated with the perception of looming threats and less so in the region involved in conditioning. Differential expression in the diencephalon suggests enhanced neuronal plasticity in barred hamlets, which might allow for rapid adjustments in their escape response, while black hamlets exhibited upregulation in genes linked to immune response and oxygen transport in the optic tectum. Overall, our findings suggest that the two species utilise different camouflage strategies, which might contribute to the maintenance of colour pattern differences and thereby influence the speciation and diversification of these closely related sympatric reef fishes.