Pigment pattern morphospace ofDaniofishes: evolutionary diversification and mutational effects

Abstract

Molecular and cellular mechanisms underlying variation in adult form remain largely unknown. Adult pigment patterns of fishes in the genus Danio, which includes zebrafish, D. rerio, consist of horizontal stripes, vertical bars, spots and uniform patterns, and provide an outstanding opportunity to identify causes of species level variation in a neural crest derived trait. Understanding pigment pattern variation requires quantitative approaches to assess phenotypes, yet such methods have been mostly lacking for pigment patterns. We introduce metrics derived from information theory that describe patterns and pattern variation in Danio fishes. We find that these metrics used singly and in multivariate combinations are suitable for distinguishing general pattern types, and can reveal even subtle phenotypic differences attributable to mutations. Our study provides new tools for analyzing pigment pattern in Danio and potentially other groups, and sets the stage for future analyses of pattern morphospace and its mechanistic underpinnings.

Developmental plasticity and variability in the formation of egg‐spots, a pigmentation ornament in the cichlid Astatotilapia calliptera

“…It appears likely that egg‐spot development largely self‐organizes by cellular interactions, and is initiated by iridophores, similar to the well‐studied zebrafish stripes. With previously undescribed cellular morphologies and behaviors including variably contracting xanthophores, iridophore‐xanthophore associations, and transparent ring clearance, egg‐spot formation lends further evidence to the suggestion that pigment cells and their interactions may be evolutionarily labile (Kelley et al, 2013; McCluskey et al, 2021; Singh & Nüsslein‐Volhard, 2015). Moreover, that egg‐spot formation can initiate regardless of the stage of background xanthophore‐based pigmentation indicates that background pigmentation and egg spot patterning are not interdependent.…”

Developmental plasticity and variability in the formation of egg-spots, a pigmentation ornament in the cichlidAstatotilapia calliptera

“…It appears likely that egg-spot development largely self-organises by cellular interactions, and is initiated by iridophores, similar to the wellstudied formation of zebrafish stripes. With previously undescribed cellular morphologies and behaviours including variably contracting xanthophore-like cells, iridophore-xanthophore associations, and transparent ring clearance, egg-spot formation lends further evidence to the suggestion that pigment cells and their interactions may be evolutionarily labile (Kelley et al, 2013;McCluskey et al, 2021;Singh and Nüsslein-Volhard, 2015). Moreover, the fact that eggspot formation can start regardless of the stage of background xanthophore-based pigmentation development contradicts a key tenet of zebrafish stripe formation in which contributions from all aspects of pigmentation are required for the pattern to emerge (Patterson and Parichy, 2019).…”

kcnj13regulates pigment cell shapes in zebrafish and has diverged by cis-regulatory evolution betweenDaniospecies

“…The specification and differentiation of pigment cells are similar in D. rerio and D. aesculapii . They both require Mitfa and Kit signalling in melanophores and Csf1 and Ltk signalling in xanthophores and iridophores, respectively ( McCluskey et al, 2021a ; Podobnik et al, 2020 ). Mutants indicate that iridophores do not emerge along the horizontal myoseptum, are lower in number and dispensable for bar formation in D. aesculapii , whereas they guide stripe formation in D. rerio ( Podobnik et al, 2020 ).…”