PerspectiveEvolution

How fish get their stripes—again and again

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Science  26 Oct 2018:
Vol. 362, Issue 6413, pp. 396-397
DOI: 10.1126/science.aav3373

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Summary

Conspicuous or otherwise elaborate color patterns sported by fishes, which constitute half of all living vertebrates, are among the most fascinating, varied, and intricate of nature. The importance of coloration for fishes can be appreciated from its many roles in camouflage and communication. The molecular and cellular mechanisms underlying color pattern development and evolution in teleost fish have received considerable attention, mostly through work in the zebrafish, Danio rerio, and its relatives. In these species, adult horizontal stripes, vertical bars, and spots along the body are formed by the timely expression of relevant genes and the orderly migration and interactions between three cell types originating from embryonic neural crest precursors: dark melanophores, yellow and orange xanthophores, and iridescent iridophores. These cells migrate to their final destination in the hypodermis and interact with each other at short and long ranges, and with their tissue environment, to produce color patterns predicted by Turing reaction–diffusion models, in which periodic patterns are produced by the interaction of an activator and an inhibitor (16). On page 457 of this issue, Kratochwil et al. (7) show that the degree of expression of the newly identified color pattern gene, agouti-related peptide 2 (agrp2), in the skin acts as a molecular switch mechanism controlling the presence or absence of horizontal melanic stripes in African cichlid fish.