Flounder with partial intestine osmoregulate in seawater

Summer flounder ( Paralichthys dentatus ) that survived flounder infectious necrotizing 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 intestine healed and became a blind pouch. We sampled the fish three months after the epizootic ended, demonstrating that these fish survive with only a portion of their intestine. We hypothesized that salt and water balance would be disturbed in the survivors of FINE. However, plasma osmolality and concentrations of Na + , Cl − , and K + were the same in intact flounder and those with only an intestinal stump. No compensatory changes in gill Na + , K + -ATPase activity were detected. The fish with intestinal stumps continued to feed, but their body weight was only 41% that of intact fish. Summer flounder can maintain salt and water homeostasis, but fail to thrive, using only one-third of their intestine.