On the relation between movements and the shape of somites in early embryos of the teleost Brachydanio rerio

As a working hypothesis it is supposed that in the teleost Brachydanio rerio, the muscle contractions, the growth, and probably some other factors, cause the first changes in the shape of the somites. Furthermore, the movements of the embryo could yield the forces by which the somites are brought to their theoretically optimal shape. In order to test this hypothesis, we investigated the somite shape and structure of spontaneously immobile embryos. Although the results are difficult to interpret, they certainly do not contradict the hypothesis. For further analysis we applied two kinds of lesions in order to immobilize early embryos: removal of the brain, and damage to the midbody somites. The results of these experiments indicate that both the development of the shape of the somite and the arrangement of the muscle fibres are dependent on movements of the embryo.