ON THE KIDNEY OF THE SAFFRON COD, ELEGINUS GRACILIS, AND ITS COLD ADAPTATION

Abstract: The structure and seasonal variations of the kidney of the saft'ron cod, Eleginus gracilis, were investigated by light microscopy. The kidney is glomerular with nephron that consists only of proximal and col-lecting tubules. The glomeruli of fish collected in February showed atrophy and did not contain blood cells. By contrast, the glomeruli of fish collected in July were well vascularized and contained some blood cells. These results may suggest seasonal changes in glomerular function with a reduced or non-functional condition of the glomeruli during winter when kidneys are phys-iologically similar to those of aglomerular fishes. These morphological differences in the glomeruli of E. gracilis may be related to the conservation of antifreeze glycoproteins in their sera and to the adaptation for cold water during the winter. 1