Oxygen deficiency during somitogenesis causes centrum defects in red sea bream, Pagrus major (Temminck et Schlegel)

摘要

Vertebral deformities in red sea bream, Pagrus major, remain serious obstacles to the improvement of seedling quality for its aquaculture. However, the causalities of the deformities remain unclear and prevention methods have not yet been established. In this paper, oxygen deficiency during somitogenesis was demonstrated to cause centrum defects (formerly called fused vertebrae in many cases), which are the major vertebral deformity in cultured red sea bream. An induction experiment of centrum defects was conducted by placing fertilized red sea bream eggs under low dissolved oxygen conditions (10.3-16.6%). The low oxygen treatment was carried out for five different developmental stages of embryo: two-cell stage to blastula stage; gastrula stage; three to 10 somites stage; 11-17 somites stage and 18-24 somites stage. Oxygen deficiency during somitogenesis induced a high incidence of centrum defects. In contrast, it hardly induced centrum defects during the other stages. The dissolved oxygen concentration in the rearing water should be carefully regulated for fertilized eggs, especially during somitogenesis to reduce the incidence of vertebral deformities in the red sea bream.