Pollutant-induced changes in fish pigmentation and spatial patterns

TL;DR

This study models how environmental pollutants disrupt fish pigmentation patterns by affecting pigment cell interactions, revealing potential mechanisms behind observed abnormalities and their dependence on exposure duration.

Contribution

It introduces a reaction-diffusion-advection model with nonlocal interactions to explain pollutant-induced pigmentation pattern changes in fish.

Findings

Pollutants alter cell adhesion and repulsion, causing pattern transitions.

Early exposure effects may be reversible, prolonged exposure leads to persistent changes.

Contaminants influence stripe formation, number, and pigmentation levels in growing fish.

Abstract

Pigmentation abnormalities, ranging from hypo- to hyperpigmentation, can serve as biomarkers of developmental disruption in fish exposed to environmental contaminants. However, the mechanistic pathways underlying these alterations remain poorly understood. Studies have shown that pattern formation in fish development requires specific pigment cell interactions. Motivated by experimental observations of pigmentation alterations following contaminant exposure, we investigate how pollutants influence pigment cell self-organization using a continuum reaction-diffusion-advection framework. The model incorporates nonlocal Morse-type kernels to describe short- and long-range interactions among melanophores and xanthophores. Our results show that perturbations to the strengths of adhesion or repulsion can drive transitions between stripes, spots, and mixed patterns, reproducing phenotypes characteristic of fish pigmentation mutants. In particular, homotypic interactions are sensitive to contamination, leading to pronounced changes in melanophore density and resulting pigmentation patterns. Time-dependent simulations indicate that pigment changes from early short-term contaminant exposure may be recoverable, whereas prolonged exposure can lead to sustained pigment loss. In a growing fish, contaminant-induced changes in cell-cell interactions directly influence stripe formation rate, stripe number, and pigmentation levels. Overall, our study provides insight into the mechanistic link between experimentally observed pigmentation alterations and the changes in spatial patterns of adult fish.