Taurine in Ruditapes philippinarum: tissue distribution, developmental dynamics and metabolic mechanism

Bivalves, although often overlooked as a source of taurine in the diet, have tissue levels of taurine that are notably higher than those in most vertebrates. However, the handling and metabolism of taurine in bivalves is still poorly understood. In the present study, we analyzed the tissue distribution of taurine in the clam Ruditapes philippinarum and evaluated the transcription of genes involved in its metabolism. Taurine concentrations differed significantly among tissues, with the gill displaying tissue concentrations more than three times higher than those in the digestive gland. Furthermore, it was demonstrated that taurine concentrations in microalgal feeds commonly employed in aquaculture are low. Clams may mitigate this deficiency by progressively accumulating taurine or related amino acids through prolonged consumption of microalgae. Additionally, our results confirmed that clams maintain continuous taurine biosynthesis throughout development, with the highest expression of taurine biosynthesis-related genes observed at the pediveliger stage. The amino acid composition of clams demonstrated significant dynamic variations throughout their development, with fluctuations in taurine precursors (cysteine, methionine, and serine) closely aligning with the expression patterns of genes involved in taurine biosynthesis. Collectively, these findings offer new insights into the tissue distribution of taurine in bivalves, emphasizing the significance of sustained taurine biosynthesis and accumulation in supporting their developmental processes and physiological functions.