Skeletal deformities of the gilthead sea bream (Sparus aurata, L.): study of the subcommissural organ (SCO) and Reissner's fiber (RF).

A high incidence of lordotic curvatures has been detected in commercial cultures of Sparus aurata. We have studied juvenile and adult lordotic specimens to elucidate whether the subcommissural organ and its secretion, the Reissner's fiber, play any role in the development of this syndrome. Animals were X-radiographed and then the brain and spinal cord dissected out and processed for light microscopy. Adult lordotic fishes had a well developed swim-bladder whereas juvenile did not. The central canal of the spinal cord showed dramatic alterations, and an altered Reissner's fiber was always present. Our histochemical results suggested a hyperactivity of the subcommissural organ in lordotic fishes.