The accumulation and metabolism of amino acids by Biomphalaria glabrata, a freshwater pulmonate snail

Abstract

Freshwater pulmonate snails ( Biomphalaria glabrata), pre-treated under bacteriostatic conditions, were incubated in 10 ml of standard medium containing various U- 14C-labelled amino acids at concentrations of 10 μM. Measurements of mass-specific accumulation rates (MSARs) based on HPLC and the accumulation of U- 14C-labelled amino acids into snail tissues have shown unequivocally for the first time that freshwater snails achieved a net accumulation of all the amino acids tested, including aminoisobutyrate (AIB), aspartate, alanine and a mixture of 13 amino acids. There were no significant differences between the MSAR values determined by HPLC from those based on the use of radiolabelled amino acids, whereas MSAR values for control snails were negligible and significantly less. Incubation of snails in media containing radiolabelled aspartate and a mixture of amino acids showed that the accumulated amino acids were readily distributed through the snail’s tissues and then metabolized. The ecological and biochemical questions arising from the fact that freshwater snails are capable of net accumulation of exogenous amino acids at naturally occurring concentrations and subsequent metabolic conversion, contrary to widely held views, are addressed.