Structure and Function of the Crustacean Larval Salt Gland

Publisher Summary This chapter explores that halobionts are organisms that can live, reproduce, and complete their life cycle in concentrated brines. These organisms can be phylogenetically quite diverse, ranging from the primitive halobacteria and unicellular algae to complex vascular plants and animals. A harsh environmental habitat, such as is found in inland salt lakes and coastal salterns, usually demands that organisms evolve special adaptations to osmotic stress to maintain water and electrolyte balance compatible with their life cycle. For halobionts which seek “osmotic conformity,” life is sustained in large measure by the fact that the internal osmotic pressure within individual cells is controlled by accumulating a compatible organic solute. The chapter discusses that halobacteria achieve similar control over intracellular osmotic pressures by genetic manipulation of macromolecules that comprise the subcellular organelles. Many of the cytoplasmic proteins of halobacteria have undergone extensive amino acid substitutions, primarily in the acidic amino acids. These substitutions enable cytosolic proteins to be more functional in the presence of high intracellular inorganic osmolyte. Finally, it focuses on two classes of aquatic arthropods, the insects, and crustaceans that are among the most successful animal halobionts.