How Marine Animals Maintain Salt and Water Balance - Essay Example

Running Header: How Marine Animals Maintain Salt and Water Balance Student’s Name: Instructor’s Name: Course Code & Name: Date of Submission: How Marine Animals Maintain Salt and Water Balance Goyal and Sastry (2006, p.99) defined Osmoregulation as process that concerns all living organisms, even those inhibiting in an isosmotic media. In order to keep a proper internal osmotic concentration and eliminate dangerous osmotic pressures, there are various mechanisms of regulation that are established by marine animals. Osmoregulation is a wide event of variuos mechanisms utilized by organisms in controlling volumes of water and water movement. This is a means of maintaining the internal osmotic concentration which varies with medium of surrounding. Osmoregulation mechanism includes solute levels and internal water regulation, cellular activities and the excretory organisms. It is also highly associated with functions of homeostatic like temperature and PH regulation in which body ion concentrations and water are involved. If the content of water in body is to be sustained at the same level then the quantity of water entering should be equal the water that exits the body. Water enters the body through food, drinking water, metabolism or osmosis. The structure of cell, diffusion, osmosis and active transport are associated with Osmoregulation. The animals which withstand a wide range of concentration of salt in medium of aquatic are referred to as euryhaline species (Sumich & Morrisse, F 2004). It includes anadromous animals which move from high salt content medium (sea) to medium of low salinity (fresh water) and those that migrate from low salinity region to high salinity are referred to as catadromous. Stenohaline species have no mechanism of Osmoregulation and don’t sustain constant internal environment. Poikilosmotic varies internal osmotic pressure according to the environment. Majority of invertebrates that inhibit sea are isosmotic i.e. their external and internal concentrations of osmotic are equal. In the event protoplasma of these organisms is dilute, they still survive and execute their metabolic functions. Majority of parasitic and marine invertebrates are easily permeable to water and lose or gain water according to the medium concentration. The volume of body is not regulated and mostly these animals can either shrink or swell in proportion to their concentration of solute. Eggs of annelids and echinoderms are the examples. As some protoplasm portion includes organic molecules which are osmotic ally inactive, the pressure increase of the exernal medium don’t produce the expect amount of volume change in these animals. 7.3% of the original cell volume in unfertilized Arbacia eggs and 27.3% in fertilized eggs is osmotic ally inactive volume. Also the reason for cells not to swell as expected in dilute medium is because salt leaks across the membrane of cell, which reveals that membrane is not completely semipermeable. Various gregarians from the gut of mealworms shrink and swell depending on medium tonicity (Goyal & Sastry 2006, p. 113). Various multi-cellular invertebrates also exhibit poor regulation of volume. The golfingai body weight increases or decreases on movement to low or high concentrations and attain the equilibrium in few hours. The initial volume of body is regained on returning to seawater. Approximately 23% of the volume of body is osmotic ally inactive. Different degrees of regulation of volume are shown by echinoderms and mollusks. Doris gain volume quickly in seawater and can retain the same situation for 24 hours. In Oncidium, permeability of water is more than permeability of salt and therefore small regulation of volume. Aplysia increases weight in 75% seawater for 2 to 3 hours and go back to normal condition after moving to pure seawater, revealing that it had lost salts when recovering. Echinoderms such as ophiuroids, asteroids and echinoids cannot swell considerably because of their hard exoskeleton. The holothurian, caudina, enlarges in seawater that is dilute but swell is very little. Osmoregulation in hypotonic environment includes several crabs species and elasmobranch fishes whose blood is hypertonic to seawater (David 1998). They usually encounter the issue of water entry and salt losses through outward diffusions. In these cases, these creatures would either lose a lot of salt or swell that their internal fluids will not sustain the normal functioning of body cells, if controlling devices are not established. Since the salt content of cells and fluids is very little in freshwater, the adaptation device is vital. The blood in Anodonta is isotonic with 0.1% solution of sodium chloride. The osmotic problem is lowered by minimized concentration of salt. The body fluids salinities of some freshwater and marine species are compared with concentration of salt in the outside environment. Body wall impermeability is vital in regulation of water entry. In birds, aquatic reptiles, adult insects, insect larvae and mammals, the wall of body is completely impermeable and membranes of exchange don’t come in contact with water. Internal hydrostatic pressure is created by osmotic water entry, which then creates elevated filtration pressure, leading in large volume of urine production in freshwater animals (David 2008). Urine loss aids in volume regulation and thus regulation of internal pressure is within range. Homoiosmotic organisms preserve a constant salt concentration in fluids of body because of salt contained in urine. The concentration of salt is preserved by active reabsorption of urine salt by tubules of the kidney. Majority of animals in freshwater have well established tubules in comparison to forms of marine where they are absent or shorter. Freshwater teleosts have nephiridia to retake salts. Also reabsorption happens in freshwater elasmobranchs. The urine excreted by fresh water animals is hypotonic to body fluids of animals since salts are absorbed in the tubules of kidney. The dilute urine excretion occurs in animal of freshwater such as mosquito larvae, earthworm, Nereis diversicolor, amphibians and freshwater fishes. In Euryhaline and Poikilosmotic animals, the body fluids osmotic concentration varies with the surrounding seawater osmotic concentration. The animals may lose or gain water until internal medium attains isotonic with seawater. The animal may shrink or swell depending on whether the surrounding medium is hypertonic or hypotonic. The sipunculid worms body wall act as a semipermeable membrane which is permeable to water but not salts. The same condition happens in marine mollusk such as Doris, oncidium and Mytillus. The other method is salts excretion. The osmotic concentration of internal medium is lowered by loss of salts to attain isotonic with seawater, and eliminate more entry of water. Water is taken in before the salt excretion in turn causing weight increase and swelling of the animal. Examples are Aplysia, marine mollusk and Nereis diversicolor. Protozoans don’t encounter any osmotic challenge whether in marine or freshwater. Parasitic and marine protozoa are isosmotic with surrounding, and only remove water which gets in with food substances. Protozoans in freshwater are hyperosmotic to their surrounding and the excessive water is removed by contractile vacuole. Amoeba lacerate inhibits comfortably in either seawater or freshwater. Paramecium woodruff can adapt in seawater. Vascular output and volume change affect protozoans Osmoregulation. Amoeba lacerata and Amoeba mina are brackish water and marine forms but exhibit good regulation of volume within a few hours after moving to freshwater (William, Bernd & Thewissen 2000, p. 75). The protozoans surfaces are permeable to water. The organism swells as a result of water entry. Measurement of permeability is measured in volume of water getting in per cell membrane unit for an osmotic gradient in certain time period. Protozoans may gain water either through surface or feeding. In four groups of protozoa which inhibits in freshwater, a contractile vacuole is constantly present, while it may exist or lack in endoparasitic and marine forms. In parasitic and marine protozoans , the contractile vacuole removes food water and metabolic water. Also some water is necessary to remove excess salts. Brackish waters are mixohaline between 0.% to 30% salinity. The forms of brackish can be classified into 3 groups; forms of marine with low salinity tolerance, animals in fresh water which can moderately tolerate salinities and animals in true brackish water which are not in fresh water or sea water. In forms of brackish water such as Carcinus which osmoregulates, the concentration of blood corresponds to approximately 60% sea water when inhibiting only in 15% sea water. Water enters through osmosis and salt loss by diffusion when the body fluid concentration is greater than the environment medium. Water is removed rapidly from body and solutes are return in order to maintain balance. Water is eliminated through urine and other means. Hypo-osmotic regulators are animals that sustain body fluid salt concentration lower than that of the outside environment. Animals living in saline water in inland waters can be categorized into 2 groups; animals in moderate saline, freshwater or low saline brackish water and animals which inhibit in elevated salinities. The challenges in hyperosmotic medium are salt gain by diffusion and water loss by exosmosis. To sustain equilibrium the animal conserve water and salt is eliminated into surrounding water through secretion. Brine shrimp and teleosts secrete salt into environment medium without losing water (Pat, Stone & Johnston, 2000). The teleost fishes inhibiting in sea water face challenge of water loss. Their body fluid is hypotonic to seawater. The skin of these fishes is coated with mucus and scales which are impermeable and water can only be removed through gills and gut. The loss of water through osmosis is regained by excreting the salt extra-renally and drinking seawater. The water and salts are absorbed rapidly by the wall of gut and seawater salt elevates the blood salinity, approximately 3.5%, while fish tissues are adapted for little salts concentrations. Kidney is unable to excrete urine which is hypotonic to body fluids, thus salt is eliminate through gills, higher than that gets in the body. The additional salts are removed from body through chlorine secretory cells in gills. The process requires metabolic energy because it involves removing salts from blood that is dilute into seawater which is against gradient of concentration. Various adaptations of anatomy are utilized to produce very little urine in the teleosts of marine. Glomeruli are mostly entirely or partially eliminated because of the lowered requirement for filtration. Marine crabs, are stenohaline and concentration of their blood varies with variations in seawater (Kamleshwar & Shukla n.d, p. 123). Examples of theses animals are; portunus, Hyas, Palinurus and Maia. The organs of renal function are well established and are in the front segment of the second antenna. These organs are referred as green glands or antennary glands. Maia dies in few hours in seawater of 20%. When moved to the dilute seawater, animal gains water at a rate that increases weight by 2.4% and salt lost from body. The blood becomes isotonic in relation to environment. The decrease of osmotic pressure stops entry of more water. The kidney is initiated by extra water to perform at high rate and after 3 hours, the crab weight reduces. The urine removed in huge quantities removes magnesium, calcium, sulphates and chloride. The blood with reduced salts will not maintain the tissues of the animal and fatality results. Osmoregulation in animals helps them to inhibit in various environment conditions. The water regulation allows them to inhibit in salt water, dry or moist conditions and over largely varying temperatures. Bentley (2002, p.155) suggest that Osmoregulation in mammals is highly related with control of water and salt in body. References Bentley, P 2002, Endocrines and osmoregulation: a comparative account in vertebrates, 2nd edn,GmbH, Heidelberg. David, H 1998,The physiology of fishes, CRC Press, Florida. David, H 2008, Osmotic and ionic regulation: cells and animals, CRC Press, Sound Parkway, USA. Goyal, K & Sastry, K 2006, Animal Physiology, 6th edn, Rajsons Printers, New Delhi. Kamleshwar, P & Shukla J n.d, Regulatory Mechanism in Vertebrates, Rajson Printers, New Delhi. Pat, W, Stone, G & Johnston ,A 2000, Environmental physiology of animals, Blackwell Science Ltd, Oxford. Sumich, L & Morrisse, F 2004, Introduction to the biology of marine life,Jones and Burtett Publishers Inc., USA. William, F, Bernd, G & Thewissen, M 2000, Encyclopedia of marine mammals, Elsevier, MA: Burlington. Read More