Concentrations of elements in tissues of four species of Tridacnidae

Concentrations of eighteen elements in several tissues of four species of Tridacnidae from coral reefs off Ishigaki Island, Okinawa, Japan, were measured by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. The highest concentrations of Ca, Cd, Co, Mn, Ni, P, Pb, Sr, and Zn were found in the kidney of Tridacnidae. In particular, the concentrations of Mn and Ni in the kidney were approximately one hundred times higher than those in other tissues. Microscopic observation of the kidney showed that intracellular granules with concentric rings were present in each cell. The granules (ca. 20μm in diameter) occupied more than a fourth of the vacuole space in the kidney cells. The concentrations of Ca, Mn, P and Sr in the granules were several times higher than those in the kidney. From these results it was concluded that the specific accumulation of Ca, Mn, P and Sr in the kidney of Tridacnidae was related to the presence of metal-containing granules.