osmoregulation

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osmoregulation

 [oz″mo-reg″u-la´shun]
adjustment of internal osmotic pressure of a simple organism or body cell in relation to that of the surrounding medium. adj., adj osmoreg´ulatory.

osmoregulation

(ŏz′mə-rĕg′yə-lā′shən)
n.
Maintenance of an optimal, constant osmotic pressure in the body of a living organism.

os′mo·reg′u·la·to′ry (-lə-tôr′ē) adj.

osmoregulation

the control of OSMOTIC POTENTIAL or WATER POTENTIAL in organisms. Water molecules tend to move from an area of high osmotic or high water potential (low osmotic pressure) to an area of low osmotic potential or low water potential (highosmotic pressure), when separated by a differentially permeable membrane. Where cells are bathed in a solution, water tends to cross the cell membrane in order to equalize the water potential on either side.

In a dry atmosphere or the marine environment, organisms tend to lose water to their surroundings. In a wet atmosphere or in freshwater, organisms may have difficulty in losing water. Various means are thus adopted to maintain a correct water balance. Xerophytic plants (see XEROPHYTE).may reverse the normal stomatal rhythm, develop a waxy cuticle, fold leaves, store water (succulent plants) or survive dry periods as spores or seeds. Excess water may be removed by GUTTATION in some plants, and by CONTRACTILE VACUOLES in some unicellular organisms. In mammals osmoregulation is carried out by the kidney, water passing out of the blood stream into the kidney tubule via the BOWMAN'S CAPSULE and reabsorbed, where necessary, in the tubule itself. Marine fish, reptiles and birds are able to eliminate salt through special excretory cells. Different groups of animals remove NITROGENOUS WASTE in different ways - all associated with osmoregulation. Many marine organisms have blood that is ISOTONIC with sea water, and so do not have an osmoregulatory problem.

References in periodicals archive ?
Potassium is key osmoregulator which plays a major role in maintaining the cellular water balance under osmotic stress conditions and reduced supply of potassium causes a decrease in leaf water potential.
As an osmoregulator, Litopenaeus vannamei has a strong ability to regulate its osmotic pressure and blood ions in a certain level when exposed to an ambient salinity change, during which they need much more extra energy (Pante 1990, Pequeux 1995).
Effects of CaCl2 on growth and osmoregulator accumulation in NaCl stressed cowpea seedlings.
Proline act as a osmoregulator, maintain membrane integrity and affect the solubility of various proteins due to its interaction with hydrophobic residues on the protein surface under the conditions of reduced water availability (Hare, 1995).
Discriminating between an extremely weak osmoregulator and an osmoconformer on the basis of hemolymph osmolality alone can be difficult, and it may be necessary to examine gill ultrastructure to draw definite conclusions (Pequeux, 1995).
We can assume that if this species--considered a good iono- and osmoregulator with a high metabolic capacity--is affected by ocean acidification, organisms without these features might be affected even more.
The blue crab Callinectes sapidus is a very efficient osmoregulator (Tan and Van Engel, 1966; Lynch et al., 1973) and can live in a range of salinities from hypersaline lagoons to fresh water (Hedgpeth, 1967; Mangum and Amende, 1972).
This distinction is important because taurine acts as an osmoregulator in many marine organisms (Thurston et al., 1980).
The authors mention that the mercury interacts with an osmoregulator mechanism impeding the animal osmoregulator capacity, increasing, then, the toxicity of metal increasing in low salinities and decreasing in high salinities.
For other osmoregulator decapods it has been demonstrated, that salinity did not have a pronounced effect on the oxygen consumption if the experimental organisms were acclimated to salinities and if these are not extreme (Bishop et al.
Sodium and proline accumulation as osmoregulators in tolerance of sugar beet genotypes to salinity.