# Distinct genetic origins of eumelanin levels and barring patterns in cichlid fishes

## TL;DR

This study explores the genetic basis of color patterns in cichlid fish, revealing distinct genetic regions that control pigmentation levels and bar spacing.

## Contribution

The study identifies 48 genetic loci linked to pigmentation and bar patterns in cichlids, showing these traits are genetically independent.

## Key findings

- Genomic regions affecting eumelanin levels are separate from those controlling bar spacing.
- Candidate genes include those involved in melanophore survival and pigment distribution.
- The findings highlight how genetic variation contributes to pigment diversity and speciation.

## Abstract

Pigment patterns are incredibly diverse across vertebrates and are shaped by multiple selective pressures from predator avoidance to mate choice. A common pattern across fishes, but for which we know little about the underlying mechanisms, is repeated melanic vertical bars. To understand the genetic factors that modify the level or pattern of vertical barring, we generated a genetic cross of 322 F2 hybrids between two cichlid species with distinct barring patterns, Aulonocara koningsi and Metriaclima mbenjii. We identify 48 significant quantitative trait loci that underlie a series of seven phenotypes related to the relative pigmentation intensity, and four traits related to patterning of the vertical bars. We find that genomic regions that generate variation in the level of eumelanin produced are largely independent of those that control the spacing of vertical bars. Candidate genes within these intervals include novel genes and those newly-associated with vertical bars, which could affect melanophore survival, fate decisions, pigment biosynthesis, and pigment distribution. Together, this work provides insights into the regulation of pigment diversity, with direct implications for an animal’s fitness and the speciation process.