The effect of diet on melanin pigmentation in animals

Abstract

Melanin, including both eu‐ and pheomelanin forms, is the most common pigment type in animals and plays numerous adaptive roles. However, the effect of diet on melanin pigmentation is not well reviewed or synthesized. Understanding how diet influences melanin may lead to valuable insights such as explaining intraspecific variation or explaining when melanin‐based traits are plastic or condition dependent versus when they are prioritized or canalized. In order to assess the state of the literature and the current understanding of the effects of diet on melanin pigmentation we conducted a systematic literature search. We use the search results to highlight common patterns across animals. In particular we focus on three questions: Which dietary components can influence melanin? Which aspects of melanin‐based traits are influenced by diet? What factors can mediate the influence of diet on melanin? The effect of diet on melanin is complex and multifaceted. Diet itself can vary in a number of ways including diet quantity, protein content, fatty acid content and amount of metals and other micronutrients. We discuss the mechanisms by which these components influence melanin pigmentation. Diet can influence the size, darkness and colour of melanin‐based traits. Often, diet influences one of these aspects but not another, which may reflect the processes of melanin synthesis and distribution. Factors that mediate whether melanin pigmentation responds to dietary variation include the type of trait, life stage, sex and environmental stress. Methodology (e.g. degree of manipulation relative to natural conditions) can also influence results. These nuances should be considered when developing hypotheses about the effects of diet on melanin pigmentation. We conclude with important areas for future research, including the proximate mechanisms connecting diet and melanin, how diet affects internal melanin, how diet mediates costs of melanin pigmentation and how diet affects the evolution of melanin‐based traits. Overall, diet has important and complex effects on melanin and likely plays an important role in the ecology and evolution of melanin pigmentation. Read the free Plain Language Summary for this article on the Journal blog.

Rodents show darker and redder coloration in warm and rainy environments

“…This observation suggests a potential connection between the coloration of these rodents and background matching with the soil, reinforcing the idea that reddish pelage could provide a camouflage advantage in warm and wet regions. Secondly, the environmental conditions in warmer and wetter regions, which may harbour higher food abundance, could potentially influence the production of intense pheomelanin pigmentation, such as carotenoids (Britton & Davidowitz, 2023). While dietary effects on pheomelanin pigmentation appear to be more relevant for birds' plumage (Delhey et al., 2023; Hill et al., 2002; Rodríguez‐Martínez & Galván, 2020), their impact on mammal pelage remains elusive (Britton & Davidowitz, 2023).…”

“…Secondly, the environmental conditions in warmer and wetter regions, which may harbour higher food abundance, could potentially influence the production of intense pheomelanin pigmentation, such as carotenoids (Britton & Davidowitz, 2023). While dietary effects on pheomelanin pigmentation appear to be more relevant for birds' plumage (Delhey et al, 2023;Hill et al, 2002;Rodríguez-Martínez & Galván, 2020), their impact on mammal pelage remains elusive (Britton & Davidowitz, 2023).…”

Exposure to ultraviolet‐B radiation increases the susceptibility of mosquitoes to infection with dengue virus

“…Since early life stages undergo rapid cell replication, unrepaired DNA damage is more likely to result in mutagenic and epigenetic modifications, which may have persisted into the adult life stage causing physiological dysfunction in adult immune and reproductive systems (Ceccato et al, 2016; Cramp & Franklin, 2018). The carryover effects of larval UVBR exposure on adult females could also be the result of energy allocation trade‐offs, which arise because mounting UVR defences is energetically costly (Britton & Davidowitz, 2023; Ceccato et al, 2016; Cramp et al, 2022). Indeed, mosquito larvae exposed to UVBR have elevated metabolic rates (Villena et al, 2018), which could explain the delayed rate of development we observed in both our experiments, albeit a short delay in our second experiment.…”

A high-quality, long-read genome assembly of the whitelined sphinx moth (Lepidoptera: Sphingidae: Hyles lineata) shows highly conserved melanin synthesis pathway genes

“…Pigmentation in the cuticle and wings of insects is largely determined by the highly conserved melanogenesis metabolic pathway, including “core” melanin synthesis genes that encode the necessary enzymes ( Sugumaran and Barek 2016 ). However, while cuticular color and pattern are, in part, inherited through allelic variation, the degree of melanin pigmentation is determined by environmental variables including temperature, photoperiod, and crowding ( Francois and Davidowtiz 2020 ; Britton and Davidowitz in review ). Purifying selection drives gene sequence conservation and phenotype variation is driven largely by gene regulation, rather than allelic differences ( Kuwalekar et al .…”