A quantitative comparison of the kidneys of the landlocked sea lamprey of the Great Lakes and the anadromous sea lamprey of the Atlantic, Petromyzon marinus L.
The length and cross-sectional area of the kidneys and the elongate renal corpuscles in both marine and freshwater lamprey, Petromyzon marinus L., increase proportionately as the animal increases in length. The paired kidneys are seldom identical, with one kidney usually longer and of greater cross-sectional area. Marine males demonstrate a larger cross-sectional area of their kidneys and renal corpuscles compared with marine females of similar size. The cross-sectional areas of the renal corpuscles of freshwater and marine animals are not significantly different and hence the amount of filtration surface is the same in the kidneys of both groups of animals. The evolution of the renal corpuscle and the involvement of this structure in osmoregulation in lampreys is discussed.