OSMOREGULATION IN THE EURYHALINE FIDDLER CRAB UCA PUGILATOR: PARTICIPATION OF THE INDIVIDUAL GILLS

Abstract

Publisher Summary This chapter discusses the osmoregulation in the euryhaline fiddler crab, Uca pugilator. The Uca pugilator is a good hyperosmotic regulator in diluted sea water and in a more limited range also a hypoosmotic regulator in concentrated sea water. It is well documented that in decapode crustacea, the gills take the main part in hyperosmotic extracellular regulation. There are evidences that sodium extrusion in hyperosmotic medium takes place in the gills. In the posterior gills of animals adapted to normal sea water, the specific activity of ATPase is 2.5–5 times higher as in the anterior gills. The specific activity of succinicdehydrogenase does not increase in the posterior gills whereas in the anterior gills, it is actually diminished significantly. This may be because of the fact that the protein is increased. In concentrated medium, a tendency of decrease of both enzyme activities is noticed. Light and electron microscopic studies prove that the anterior gills have a thin single-layered epithelium with few cell organelles and poorly differentiated membranes. The cells show typical structures of a salt transporting epithelium like deep basal and remarkable apikal infoldings of the plasma membranes.