Fluid reabsorption in the crayfish kidney labyrinth.

Abstract

AbstractIn the crayfish, eyestalk extirpation produced noticeable blood dilution within three to four hours when maintained in tap water. Microscopic examination of kidney labyrinth cells following this treatment revealed an increase in the width and number of intercellular spaces and a decreased cell volume. Conversely, exposure of the intact animal to 50% sea water for the same interval concentrated the blood, and intercellular spaces and cell volumes did not change. Finally, with both treatments together (i.e., eyestalk extirpation and immersion in 50% sea water), blood became concentrated, but intercellular spaces increased in width and cells shrunk, as occurred with eyestalk extirpation alone. Effects of these whole‐animal treatments on mitochondria, intracellular compartments and basal invaginations among labyrinth cells are also noted. The findings suggest two conclusions. First, it is proposed that the dilation of intercellular spaces is due to an efflux of fluid from the cells into the lateral compartments. Such movements may be part of a mechanism effecting isotonic transepithelial fluid flow from lumen to blood as demonstrated in other systems. Second, since eyestalk extirpation is known to induce hormonal conditions simulating ecdysis, and since the morphological changes in the labyrinth following extirpation occur whether the blood has become diluted or concentrated, it is suggested that solute reabsorption by the crayfish kidney is under direct hormonal control. Such a mechanism could be especially useful during molt‐induced water uptake to enhance reabsorption of solutes and prevent loss of fluid.