Effects of starvation and infection with Schistosoma mansoni on the release rate of free amino acids (FAA) by Biomphalaria glabrata.

1. The elimination of dissolved free amino acids (FAA) by individual snails during a period of 2 hr was measured. The FAA concentration in the hemolymph and in the homogenate also was determined. 2. For uninfected, normally fed snails a daily FAA production of 0.7 +/- 0.25 mumol glycine equivalents/g live wt was found. With snails starving for 7 days the daily FAA release rate fell to a mean value of 0.44 +/- 0.19 mumol glycine equivalents/g live wt. Infection with Schistosoma mansoni, however, induced higher FAA loss with an average of 1.72 +/- 1.07 mumol glycine equivalents/g live wt/day. 3. The FAA concentration in the homogenate of both starved and infected B. glabrata was significantly reduced by comparison to the levels found for normally fed snails. 4. A clear drop in FAA concentration was found in the hemolymph of starved and infected snails, respectively. 5. The FAA concentrations in the hemolymph and the homogenate of parasite-bearing snails does not differ significantly from the results found for starved snails. By contrast, the FAA release of infected B. glabrata significantly increased in comparison to that of the starved snails.