Experimental studies on the caudal neurosecretory system of Tilapia mossambica

Abstract

1. 1. In the absence of the urohypophysis, Tilapia mossambica exposed to salt water (1.7% NaCl) show higher mortality, greater loss of body weight, increased serum chloride and increased number of paraldehyde fuchsin-staining cells in the preoptic nucleus, as compared with control fish. 2. 2. Depletion of neurohypophyseal and urohypophyseal neurosecretion was an inconsistent response of some fish in all experimental groups exposed to the salt-water environment. 3. 3. Attempts to replace the extirpated urohypophysis with an acetone-dried preparation of the terminal spinal cord material were not successful in preventing mortality and loss of body weight among fish exposed to salt water. However, serum chloride levels were lower in salt-treated fish receiving the “urohypophyseal” preparation. 4. 4. Goldfish exposed to salt water also showed increased loss of body weight and a tendency toward and increase in number of stainable preoptic nucleus cells after urohypophysectomy. 5. 5. A relation, direct or indirect, between the caudal neurosecretory system and osmotic or ionic regulatory mechanisms is strongly suggested, but its nature remains unknown.