VEILLETTE, PA*; BREVES, JP; REARDON, DR; SPECKER, JL; University of Rhode Island; University of Rhode Island; University of Rhode Island; University of Rhode Island: COMPENSATORY HYPERTROPHY IN FLOUNDER GUT

We investigated the osmoregulatory physiology of the marine teleost summer flounder (Paralicthys dentatus) that had a pathologically shortened gastrointestinal tract due to necrotizing enteritis. Evidenced by undisturbed content of moisture in muscle, survivors maintain salt and water balance despite missing most of their intestine. This is surprising because the intestine is the primary site for the obligatory uptake of water in order to prevent dehydration. Rates of fluid uptake (normalized to tissue weight) across all segments of the partial gastrointestinal tract (esophagus, stomach, and remnant intestine) were either less than or similar to rates from intact, healthy cohorts. In contrast, the average total weight (percent of body mass) of the stomach or remnant intestine was about double that of the stomach or intact intestine from healthy flounder. Consequently, when fluid uptake rate was normalized to body mass, total uptake capacity was similar for both groups. Adaptive hypertrophy of the stomach and remnant intestine likely restores functional capacity of the partial gastrointestinal tract to a magnitude sufficient to maintain water balance. These results further evidence a critical role of the intestine for osmoregulatory ability of teleost fishes in a marine environment. [Supported by NSF IOB 0220196]