Flounder with partial intestine osmoregulate in seawater

Summer flounder (Paralichthys dentatus) that survived flounder infectious n ecrotizing enteritis (FINE) provided an unusual model for testing the role of the intestine in maintaining salt and water balance. The survivors lost 67% of the posterior-most intestine. The remaining stump of the anterior in testine healed and became a blind pouch. We sampled the fish three months a fter the epizootic ended, demonstrating that these fish survive with only a portion of their intestine. We hypothesized that salt and water balance wo uld be disturbed in the survivors of FINE. However, plasma osmolality and c oncentrations of Na+, Cl-, and K+ were the same in intact flounder and thos e with only an intestinal stump. No compensatory changes in gill Na+, K+-AT Pase activity were detected. The fish with intestinal stumps continued to f eed, but their body weight was only 41% that of intact fish. Summer flounde r can maintain salt and water homeostasis, but fail to thrive, using only o ne-third of their intestine.