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Mechanisms of Osmoregulation in Freshwater and Marine Invertebrates: Adaptations and Processes by zoologyverse

Explore osmoregulation in invertebrates, including definitions, classifications, and mechanisms in freshwater and marine environments, highlighting structures like contractile vacuoles and excretory organs.

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Mechanisms of osmoregulation in fresh water and marine water Invertebrates
Content • INTRODUCTION • DEFINITION OF OSMOREGULATION • TYPES OF INVERTEBRATES ACCORDING TO THE MEDIUM • CLASSIFICATION OF INVERTEBRATES ON THE BASIS OF OSMOREGULATION I. OSMOCONFORMERS II. OSMOREGULATORS • MECHANISMS OF OSMOREGULATION • OSMOREGULATION IN FRESH WATER INVERTEBRATES • OSMOREGULATION IN MARINE WATER INVERTEBRATES • CONCLUSION • REFERENCE
INTRODUCTION WITH THE HELP OF THEIR SEVERAL STRUCTURES ALL THE LIVING ORGANISMS MAINTAIN A PROPER AMOUNT OF WATER AND SALTS IN THEIR BODIES. THIS REGULATION OF THE WATER AND SALTS CONTENTS OF THE BODY IS TERMED AS OSMOREGULATION. HOWEVER, THE OSMOTIC REGULATION AND IONIC REGULATION ARE SOMETIMES TREATED AS THE DIFFERENT MECHANISMS. BUT IN MOST ANIMALS THE OSMOREGULATORY MECHANISM INCLUDES BOTH OF THEM BECAUSE THE REGULATION OF ONE(WATER) ALWAYS AFFECTS THE OTHER(SALTS).
DEFINITION OF OSMOREGULATION THE MAINTENANCE OF CONSTANT OSMOTIC PRESSURE IN THE FLUIDS OF AN ORGANISM BY THE CONTROL OF WATER AND SALT CONCENTRATION IS KNOWN AS OSMOREGULATION.
Types of INVERTEBRATES ACCORDING to the MEDIUM • INVERTEBRATES whose body fluids have same concentration as that of their surrounding medium never face the problem of OSMOREGULATION as long as they live in such a medium are called isotonice or isosmotic invertebrates. For example, most marine animals are isotonic, as they have their body fluids isotonic with sea water. • Invertebrates which live in a MEDIUM of lower salt concentration have face difficulty of hydration and hence they have evolved special mechanisms to get rid of the excess water that usually enters their body and dilutes their body fluids are called hypotonic or hhyposmotic INVERTEBRATES . For example, fresh water protozoans and crustaceans are hypotonic and eliminate the excess water bY contractile vacuoles and excretory organs respectively. • INVERTEBRATES which live in a MEDIUM of higher salt concentration have to evolve regulatory mechanisms by which excess loss of water from the body is prevented are called hypertonic or hyperosmotic invertebrates. For example, bony fishes of sea.
CLASSIFICATION of the INVERTEBRATES on the basis of OSMOREGULATION OSMOCONFORMERS- Osmoconformers are marine organisms that maintain an internal environment which is osmotic to their external environment.This means that the osmotic pressure of the organism's cells is equal to the osmotic pressure of their surrounding environment. By minimizing the osmotic gradient, this subsequently minimizes thenet influx and efflux of water into and out of cells. Even though osmoconformers have an internal environment that is isosmotic to their external environment, the types of ions in the two environments differ greatly in order to allow critical biological function to order.
OSMOREGULATORS- AN OSMEGULATORS IS AN ORGANISM THAT CAN REGULATE OR KEEP THE SOLUTES OR SALTS OF ITS BODY FLUIDS AT A HIGHER OR LOWER CONCENTRATION THAT THE CONCENTRATION OF THE SOLUTES IN THE EXTERNAL MEDIUM, ALTHOUGH THIS REGULATION MAY BE LIMITED AT EXTREMELY HIGH OR EXTREMELY LOW EXTERNAL SOLUTE CONCENTRATION. FOR EXAMPLE- MARINE OR FRESH WATER FISHES, PROTISTS LIKE PARAMECIUM ETC.
MECHANISMS of OSMOREGULATION • IN FRESH WATER INVERTEBRATES- • ALL FRESHWATER INVERTEBRATES, AS WELL AS FISHES AND AMPHIBIANS, ARE HYPERTONIC TO THE SURROUNDING WATER. SINCE THEY ARE NEVER COMPLETELY IMPERMEABLE, THEY HAVE STEADY INFLOW OF WATER AND SOME LOSS OF SALT. THEY ELIMINATE EXCESS AMOUNT OF WATER AS URINE, AND BY ELABORATING A URINE OF VERY LOW CONCENTRATION. • NUMEROUS FRESHWATER INVERTEBRATES CAN ABSORB SALT ACTIVELY AND PROBABLY ALL OF THEM HAVE SOME SALT ABSORBING MECHANISM. • FRESHWATER PROTOZOANS LIVING IN HYPOTONIC MEDIUM, ELIMINATE EXCESS WATER BY THEIR CONTRACTILE VACUOLES. THE PULSATION RATE OF THE VACUOLES INCREASES WHEN MORE WATER PENETRATES INTO THE BODY. • IN FRESHWATER CRUSTACEANS THE EXCESS WATER IS ELIMINATED BY THEIR EXCRETORY ORGANS, THE ANTENNARY OR GREEN GLANDS. • THE SMALL AMOUNT OF SALT LOST WITH THE DILUTE URINE IS RESTORED BY ACTIVE ABSORPTION OF SALTS BY THE GILLS FROM THE FRESHWATER. • FRESHWATER MOLLUSCS E.g. UNIO AND ANODONTA ALSO EXCRETE A LARGE AMOUNT OF DILUTE URINE AND ABSORB SALTUS TO MAKE UP THE LOSS. • THE FRESHWATER CRAYFISH, ASTACUS, SECRETES URINE EQUAL TO ABOUT 4% OF ITS BODY WEIGHT IN 24Hr, THE OSMOTIC CONCENTRATION OF WHICH IS ABOUT ONE FIFTH THAT OF ITS BLOOD. • AS THEY HAVE A LOW SALT CONCENTRATION, THEY HAVE NOT BEEN ABLE TO ADPOT TO A MARINE LIFE, FOR IN SALT WATER THEY WOULD BECOME DEHYDRATED AND SALT WOULD ENTER THE BODY.
In marine water INVERTEBRATES- • MOST INVERTEBRATES LIVING IN THE SEA HAVE AN OSMOTIC CONCENTRATION IN THEIR BODY FLUIDS WHICH EQUAL THAT OF THE SURROUNDING SEA WATER BUT THEY CAN REGULATE THEIR IONIC COMPOSITION. • WHEN A MARINE INVERTEBRATES IS PLACED IN DILUTE SEA WATER, THE WATER ENTERS THE ANIMALS DUE TO THE HIGHER OSMOTIC CONCENTRATION OF THE ANIMAL. BUT AFTER SOMETIME A STATE OF OSMOTIC EQUILIBRIUM IS ATTAINED WITH THE NEW ENVIRONMENT. • IF THE MEDIUM BECOMES TOO DILUTE THEY WOULD DIE. • THE ABILITY OF A MARINE ANIMALS TO PENETRATE INTO A BRACKISH WATER OR ESTUARINE ENVIRONMENT DEPENDS ON THREE DIFFERENT ABILITIES, OR A COMBINATION OF THEM. THESE ARE- (I) THE ANIMAL MAY TEMPORARILY EXCLUDE DILUTE SEA WATER, FOR EXAMPLE A CALM OR OYSTER MAY CLOSE ITS SHELLS WHEN THE CHANGING TIDES BRING HIGHLY DILUTED SEA WATER. (II) THE ANIMAL MAY TOLERATE THE DECREASE OCCURRING IN THE CONCENTRATION OF ITS BODY FLUIDS AS THE SALINITY OF THE WATER DECREASES TEMPORARILY. (III) THE ANIMAL MAY ACTIVELY TAKE UP SALT FROM THE WATER AND MAINTAIN A HIGHER OSMOTIC CONCENTRATION THAN THE SURROUNDING WATER. THIS FORM OF OSMOTIC REGULATION WILL ENABLE THE EFFICIENT ANIMAL TO LIVE IN DILUTE WATER, AND MAY EVEN PERMIT HIM TO PENETRATE INTO FRESHWATER.
OSMOREGULATION IN FRESHWATER INVERTEBRATES In amoeba The contractile vacuole eliminates excess water which comes as a by- product of respiration or enters the cell by osmosis (amoeba is hypertonic).The vacuole gradually increases in size and when full moves through cytoplasm to surface of cell where it bursts and expels the water.
In paramecium Osmoregulation in Paramecium The main function of the contractile vacuoles present in the body of the Paramecium is osmoregulat ion. The concentration of the cytoplasm is higher than that of the surrounding water and this result in endosmosis. Water diffuses in through the semipermeable pellicle.
In euglena Euglena Viridis has a semi- permeable pellicle and lives in water so that water continuously enters in its body by endosmosis. The removal of excess of water from the body is known as osmoregulation. The elimination of excess of water is done by the contractile vacuole.
In hydra 1. The rate of spontaneous column contractions in fresh- water Hydra is inversely proportional to external osmolality. 2. Hydra maintain their water balance by periodically eliminating excess water from the enteron through the mouth by contraction of their body column.
In ascaris The excretory system consists of an enormous H- shaped canal system contained within a single cell (Fig 22-17A,B). The uprights of the “H” are longitudinal canals located in the lateral epidermal cords and extend over the entire length of the worm. The two longitudinal canals connect with each other via a transverse canal near the anterior end of the worm. A short excretory duct leads from the transverse canal to the excretory pore on the anterior ventral midline. The system is thought to be chiefly osmoregulatory. The excretory canal system is difficult to observe in gross dissection of preserved whole specimens. The excretory pore is located immediately posterior to the mouth on the ventral midline but it is difficult to find.
IN PLANARIA Planaria are flatworms that live in fresh water. Their excretory system consists of two tubules connected to a highly-branched duct system that leads to pores located all along the sides of the body. The filtrate is secreted through these pores. Flame cells (protonephridia) are the part of excretory system of platyhelminthes ( flat worms) and help in excretion and osmoregulation. These are irregular shaped and send out pseudopodial processes in to the surrounding tissues. Each flame cell has a intracellular cavity in which a tuft of long cilia is present.
In pheretina A metanephridium typically consists of a ciliated funnel opening into the body cavity, or coelom connected to a duct which may be variously glandularized, folded or expanded (vesiculate) and which typically opens to the organism 's exterior. These ciliated tubules pump water carrying surplus ions, metabolic waste, toxins from food, and useless hormones out of the organism by directing them down funnel-shaped bodies called nephrostomes. This waste is passed out of the organism at the nephridiopore. The primary urine produced by filtration of blood (or a similar functioning fluid) is modified into secondary urine through selective reabsorption by the cells lining the metanephridium.
IN PERIPLANETA The Malpighian tubule system is a type of excretory and osmoregulatory system found in some insects, myriapods, arachnids, and tardigrades. The system consists of branching tubules extending from the alimentary canal that absorbs solutes, water, and wastes from the surrounding hemolymph.
OSMOREGULATION IN MARINE WATER INVERTEBRATES In ASTERIAS (Starfish)
IN PALAEMON OSMOREGULATION IN PRAWN IS BY GREEN GLANDS( ANTENNARY GLAND OR RENAL GLAND) PRESENT IN PENAEUS HAVE A DUAL FUNCTION OF EXCRETION AND OSMOREGULATION. GREEN GLAND CONSISTS- END SAC, LABRINTH, GLANDULAR TUBE, BLADDER.
In carcinus THE SHORE CRAB(CARCINUS) CAN ACTINELY RESIST CHANGES IN ITS OSMOTIC CONCENTRATION BECAUSE IT HAS THE PROCESS OF OSMOREGULATION. THE INTERNAL OSMOTIC CONCENTRATION IN THE CRAB CAUSES A STEADY INFLOW OF WATER, WHICH MUST BE ELIMINATED AGAIN SINCE THE CRAB HAS A KIDNEY, SO CALLED GREEN GLAND OR ANTENNARY GLAND WHERE WATER CAN BE EXCRETED.
Conclusion Osmoregulation means the physiological processes that an organism uses to maintain water balance; that is, to compensate for water loss, avoid excess water gain, and maintain the proper osmotic concentration (osmolarity) of the body fluids. Their are two types of organisms which are euryhaline which can tolerate the salinity and other one is stenohaline which cannot tolerate salinity. Every invertebrates having their own osmoregulatory part like contractile vacuole of protozoans, green gland of arthropods metanephridium in annelids etc. So this process is very useful for the survival of any organism.
REFERENCES • ANIMAL PHYSIOLOGY AND RELATED BIOCHEMISTRY BY H.R. SINGH • INVERTEBRATES ZOOLOGY BY R.L. KOTPAL
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