What is "osmoconformer"

n. any marine invertebrate that maintains its internal salinity such that it is always equal to the surrounding seawater

Osmoconformers are marine organisms that maintain an internal environment that is isosmotic to their external environment. This means that the osmotic pressure, or osmolarity, of the organism’s cells is equal to the osmotic pressure of their surrounding environment. By minimizing the osmotic gradient, this subsequently minimizes the net influx and efflux of water into and out of cells. Even though osmoconformers have an internal environment that's isosmotic to their external environment the types of ions in the two environments differ greatly in order to allow critical biological functions to occur. A benefit to osmoconformation is that organisms don’t need to expend as much energy as osmoregulators in order to regulate ion gradients. However, to ensure the correct types of ions are in their desired location, a small amount of energy is expended on ion transport. A disadvantage to osmoconformation is that organisms are subject to changes in the osmolarity of their environment.