ONTOGENY OF OSMOREGULATION IN CRUSTACEANS - A REVIEW

From the results of studies conducted from the 1960s, three patterns o f ontogeny of postembryonic osmoregulation in crustaceans may be disti nguished: (1) osmoregulation varies little with developmental stage an d the adults are often weak regulators or osmoconformers; (2) the adul t type of osmoregulation is established in the first postembryonic sta ge; (3) metamorphosis marks the appearance of the adult type of osmore gulation. The occurrence of osmoregulation is based on efficient ionic regulation (mainly of Na+ and Cl-) and increased levels of Na+-K+ ATP ase activity. Osmoregulatory epithelia may appear at different times o f development and at different locations of the branchial chamber. The se events are inter-related, and are correlated with changes in salini ty tolerance. In species the eggs of which are exposed to the external medium, either embryos are osmotically protected by the egg envelopes , or the egg membranes and/or the embryos acquire the ability to osmor egulate. When embryos develop in incubating pouches enclosed in the fe male's body, where they are osmotically protected, they may also becom e progressively able to osmoregulate. Throughout the development of cr ustaceans, osmoregulation appears as a key adaptative factor to one or several habitats.