The effect of heat and cold exposure on HSP70 expression and development of deformities during embryogenesis of Atlantic salmon (Salmo salar)

Temperature stress is recognized as a teratogenic factor that induces deformities during the embryonic development of teleosts. In order to further elaborate the mechanisms involved, Atlantic salmon (Salmo salar) embryos were heat (16 degrees C) and cold (1 degrees C) shocked at eight and four different embryonic stages, respectively, during the period from gastrulation until the completion of somitogenesis. Additionally, embryos were subjected to a long-term heat exposure at 12 degrees C from the similar to 1st until the similar to 20th somite stage. Real-time RT-PCR results showed that the HSP70 mRNA expression was dependent on the stage of development. Whereas temperature shock was found to induce HSP70 mRNA up-regulation at the gastrula stage, the similar to 9th, the similar to 15th, the similar to 20th and the similar to 45th somite stage, the additional three investigated stages showed no up-regulation. The highest HSP70 expression levels were induced at the similar to 45th somite stage as shown by a 12- and 4-fold increase after heat and cold shock, respectively. Embryos subjected to the prolonged heat exposure showed a stronger HSP70 expression than embryos that were given a 1-h heat shock. Intriguingly, a high incidence (17%) of situs inversus of abdominal organs was found in try subjected to the long-term exposure, supporting that early somitogenesis is an important period of left-light determination in telcosts. In general, the 1-h temperature shock was not sufficient to induce high frequencies of deformities. Though, a 14% incidence of vertebral deformities was observed both at the similar to 45th somite stage and at the completion of somitogenesis after cold shock. The results provide new insight regarding the tolerance of high and low temperature stress in Atlantic salmon embryos. (c) 2005 Elsevier B.V. All rights reserved.