OSMOREGULATION IN CLAMWORMS Essay Example | Topics and Well Written Essays - 1250 words

OSMOREGULATION IN CLAMWORMS - Essay Example They are the large common estuarines. They are also found on the brackish waters. (Oglesby, 1968). Now they are also found at Africa, coastal Europe and Southern Australia. They grow to a height of 190 mm and lives for one year. They reproduce sexually. The most important characteristic of this species is that they are able to withstand the temperature range of 12 - 35Â °C and survive at a salinity range of 65 ppt for long time and 80 ppt for short time. They are good osmoregulators. Osmoregulation is na active regulation of the osmosis pressure of the body fluids (mainly water) with that of the environmental conditions. Osmosis is maintained both by the terrestrial and marine animals. They do so by excretion through the organs such as kidney and skin. Osmoregulation is of two types, they are osmoregulators and osmo conformers. Osmoregulators are strict regulators of salt and water concentration in the body to that of the environment. osmoconformers match their body fluid concentrat ion to that of the environment.(Masterson, 2008). Neries virens species is able to withstand the salt water content from 5 % to 100%. Some studies have found that they are also able to withstand twice the salt concentration that of salt water. They are only slightly hyperosmotic whereas most of the worms are in osmotic equilibrium with the sea. Review of literature: The body fluids of Nereis are isoosmotic for the sea water. Osmoregulation is one of the important functions of the gut, dorsal pores and the body surface. The salts are transported by active transport and the water by osmosis. Osmosis is the movement of the water (solvent) from high concentration to low concentration across a semi permeable membrane. Here the cell membrane acts as the semi permeable membrane. The influence of the sea water on the weight of the body. The greater the dilution, the greater the increase in the body weight. The worm tends to accommodate itself to the new environment. After the increase in th e body weight, they tend to return back to the normal weight if they are left in the original sea water. These euryhaline osmoregulators are thus capable of surviving in reduced, increased salinity levels. They are found to show two types of blood osmo regulation. First they act as hyper osmotic in the diluted sea water with greater osmo regulatory control. Two important mechanisms are stated for this hyper osmotic capability. The transport of the body salts from the body surface to the body fluid through the medium. The second mechanism is by the reduction of the permeability of the body surface to the solutes and solvents. (Oglesby, 1968). For increasing salt concentrations of upto 2 times the salt concentration they act as hypo- osmotic. The concentration of salt in sea water is 1000 m – Osmole / liter and the blood of Nereis contains about 340 – 500 m – Osmole / liter at marine conditions and 280 – 360 m – Osmole / liter at the fresh water leve ls. The pH of the coelomic fluid was found to increase as the salinity of the water increases. If the salt concentration is higher at the outer environment, the water moves out of the body of the Nereis and thus loses its weight in order to maintain the osmotic pressure as constant. They adapt to the environment very quickly because of the well developed excretory organs. Pronephridia are the excretory and osmoregulaatory organs that are able to drive out the excess water and the waste products. (Whitton, 1975). Another study investigated the osmotic stress due to the long term assimilation and short term assimilation of salinity changes. A single worm was exposed to different salt concentration at different time intervals for a period of 14 days and the changes in weight were measured at continuous time intervals. Another worm