– DEFINITION: Enantiostasis is the maintenance of metabolic and physiological functions, in the absence of homeostasis, in an organism in response to variations in the environment.
– An estuary is where a river meets the sea, and freshwater mixes with saltwater
– In such an environment, the salinity levels are always changing dramatically.
– Organisms living in such an environment need to have mechanisms to cope with such changes in order to survive. The mechanisms are all collectively called enantiostasis.
– One strategy is to allow the body's osmotic pressure to vary with that of the environment. Organisms that do this are said to be osmoconformers (e.g. most marine invertebrates).
– Marine mammals and most fish are osmoregulators, maintaining homeostasis.
– Animals (like fish) can move to avoid changes (or shellfish opening and closing),
– Plants must have mechanisms to help them cope with these changing environmental conditions.
– One example of enantiostasis is when a change in salt concentration in the body fluid, which reduces the efficiency of an enzyme, is compensated for by a change in pH, which increases the efficiency of the same enzyme.