Evidence for developmental linkage of pigment patterns with body size and shape in danios (Teleostei: Cyprinidae)

Variation in pigment patterns in fishes is known to be subject to natural and sexual selection, but the mechanisms by which that variation is generated are only beginning to be understood. Theoretical models of pigment pattern formation in animals suggest that the size and shape of the organism at the time of pattern determination as well as subsequent growth time are important determinants of pattern. However, few data document the empirical relationship of pigment patterning with size, shape, and growth. Here we document patterns of growth in relation to pigment pattern formation in the zebrafish (Danio rerio) and six close relatives. In all species examined, establishment of adult pigment pattern within a particular region of the body is associated with a period of substantial growth and shape change in that region of the body. Furthermore, forms with more horizontal stripes on the midbody as adults (Danio rerio and D. rerio "leo") are larger at the time pigment cells begin to assume their adult pattern. Finally, continued deepening of the body as the pigment pattern develops is associated with vertical distortions and reticulations in the patterns of D. malabaricus and D. browni. These results are consistent with the predictions of theoretical models that size, growth, and shape change are critical determinants of pigment patterning, and suggest that variation in pigment pattern may arise in part through differential allometric growth between species.