Meeting Abstract

36.3  Wednesday, Jan. 5  Pattern of Variation during the Phylotypic Stage of Zebra Fish, Danio rerio. SCHMIDT, Kai*; STARCK, J. Matthias; Ludwig Maximilians University of Munich (LMU); Ludwig Maximilians University of Munich (LMU) kaiusch@aol.com

All vertebrate embryos pass through a period of morphological similarity, i.e., the phylotypic stage (PS). Possible causes of such similarity are discussed controversially and shall be tested here. First, we defined the PS for zebra fish according to patterns of morphological variation. We measured the phenotypic variance and the number of significant correlations among embryonic traits. Consequently, the phylotypic stage was characterized by the high number of internal constraints (morphological integration). Second, we studied if changes in raising conditions could elicit developmental plasticity, modularity or heterochrony during the PS. Third, we tested if additive genetic variance were reduced / exhausted during the PS. Our results show that the PS of zebra fish is constrained by multiple internal correlations among morphological characters. However, certain developmental conditions allow to recognize developmental modules, and evoke heterochrony during the PS. The heritability of embryonic traits is stable throughout early embryogenesis, thus we exclude that stabilizing selection has exhausted or reduced the additive genetic variance. We conclude that the phylotypic stage is accessible to selection, but that the overall similarity of embryos is established by multiple morphological constrains.