Net uptake of dissolved free amino acids by the giant clam, Tridacna maxima: alternative sources of energy and nitrogen?

Abstract

The role of dissolved free amino acids (DFAA) in nitrogen and energy budgets was investigated for the giant clam, ¹ridacna maxima, growing under "eld conditions at One Tree Island, at the southern end of the Great Barrier Reef, Australia. Giant clams (121.5}143.7 mm in shell length) took up neutral, acidic and basic amino acids. The rates of net uptake of DFAA did not di!er between light and dark, nor for clams growing under normal or slightly enriched ammonium concentrations. Calculations based on the net uptake concentrations typical of the maximum concentrations of DFAA found in coral reef waters (&0.1 lM) revealed that DFAA could only contribute 0.1% and 1% of the energy and nitrogen demands of giant clams, respectively. These results suggest that DFAA does not supply signi"cant amounts of energy or nitrogen for giant clams or their symbionts.