Heat shock produces periodic somitic disturbances in the zebrafish embryo

Environmental influences are known to produce segmental defects in a variet y of organisms. In this paper we report upon segmental aberrations produced by brief heat shocks delivered to developing zebrafish embryos. The initia l defects in the segmental pattern of semitic boundaries and motoneuron axo n outgrowth were usually observed five somites caudal to the somite which w as forming at the time of heat shock application. Segmental defects in zebr afish embryos exposed to a single heat shock treatment can occur in a perio dic pattern similar to the multiple disturbances observed to occur in chick embryos. These data are discussed with regard to models involving cell cyc le synchrony or 'clock and wavefront' schemes in the process of somitogenes is. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.