SCHMIDT, K.U.; STARCK, J.M.; Univ. of Munich; Univ. of Munich: Patterns of Variability during early Embryonic Development of Zebrafish, Danio rerio.

Vertebrate embryos pass through a period of remarkable morphological similarity during their early embryonic development. Here, we study patterns of embryonic variation to test ideas about modularity and internal developmental constraints. Supposedly, modularity, constrains, exhausted genetic variance, and directional selection create different pattern of variation and covariation of embryonic traits. By analyzing those patterns of variation during early embryogenesis, we will be able to recognize the underlying processes. We use the zebrafish, Danio rerio, in a quantitative breeding design, as a model organism to study changes in genetic and environment induced variability. In particular, we are looking at the embryonic development from 12 hours post fertilization until 27 hours post fertilization. During this time period, the development of individual embryos is documented at hourly intervals. Characters are maximum diameter of the eye, length of embryo number of somites, inclination of somites, and the yolk size (as a maternal effect). The coefficient of variation was used as a measure of variability that was independent of size of the organ and individual. During the observation period the coefficient of variation was always above 4 % indicating a considerable degree of (genetic) variability. Results from a correlation analysis suggest that internal constraints and a low effective modularity determine patterns of variability during early embryonic development of zebra fish while exhausted additive variance or stabilizing selection/canalization can be ruled out.