Zebrafish embryo at the 5-somite stage The cross-sectional view is in the ventral portion of the neural keel. In the lower portion of the image, somites detach from ventral mesoderm. Oriented divisions occur within the neural keel. At the level of the first somite, amoeboid cells located underneath the hypoblast migrate laterally on the surface of the yolk cell. This video made available by Mark Cooper thru Zebrafish - The Living Laboratory. The videos in this group can also be found in the Developmental Landmarks page of the Fishscope web site.