ABSTRACT
The study of branchial water permeability is linked inextricably to that of the environmental physiology of osmoregulation. The study of gill water exchanges permits comparisons of branchial permeability coefficients, enabling functional classification of the epithelium to be made and affording correlation between membrane permeability and cellular structure as a function of the environment. There is evidence that the permeability of a membrane is related to its fluidity, which is dependent on lipid composition and physical factors such as temperature. Water permeability of gills has been studied at several experimental levels: whole animal studies, experiments using in vitro perfused preparations of isolated gills or whole fish heads, isolated, ligatured gills, and single branchial lamellae mounted as a “double-epithelium” preparation between Ussing-type half chambers. In euryhaline Crustacea also, there are ultrastructural differences between the gill epithelium of high and low salinity acclimated animals, which may be associated with phenotypic differences in integumental transport capacity.
