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Swim bladder general organization and circulation and function

The document summarizes the general organization, circulation, types, gas secreting complex, and functions of the swim bladder in fish. It notes that the swim bladder contains gas and develops from the gut wall. Blood supply comes directly from arteries or the coeliaco-mesenteric artery. Depending on connections to the esophagus, swim bladders are either physostomous or physoclistous types. The anterior part secretes gas while the posterior part absorbs gas. Main functions include respiration, sound production, hearing, pressure sensing, and providing buoyancy.

Education◦
SCHOOL OF STUDIES IN ZOOLOGY JIWAJI UNIVERSITY, GWALIOR Dr. Ramkumar Lodhi Conservation Biology Lab TOPIC- SWIM BLADDER GENERAL ORGANIZATION AND CIRCULATION AND FUNCTION
SYNOPSIS  Introduction  General organization and circulation  Types of air bladder  Gas secreting complex  Functions of the swim bladder  Conclusion  Reference
INTRODUCTION  Fishes possess various structural adaptations in their body.  Swim bladder, also known as air bladder or gas bladder, is a characteristic structure in all the osteichthyes, excepting a few species in which it has been lost secondarily.  It is situated between the alimentary canal and kidneys, and is sac- like in appearance.  It contains air or gas, which is a mixture of carbon dioxide, oxygen and nitrogen, and develops as a small outgrowth from the dorsal or lateral wall of the gut.
CIRCULATION  Blood supply of the air bladder-:  The air bladder is supplied with blood either directly from the dorsal aorta or from branches of the coeliaco- mesentric artery.  The venous blood is drained into the hepatic portal system or into the posterior cardinal vein.  The gas bladder does not present a uniform pattern and degree of vascularity in a various species.  In species belonging to the clupeidae and salmonidae, there is a uniform distribution of blood capillaries over the bladder wall, and red bodies or red glands are not form.
TYPES OF SWIM BLADDER  Depending on the presence of the duct (ductus pneumaticus) between the swim-bladder and the oesophagus, the swim-bladder in fishes can be divided into two broad categories: Physostomus and Physoclistous types-:  Physostomous Condition:  The swim-bladder develops from the oesophagus. When the ductus pneumaticus is present between the swim-bladder and the oesophagus, the swim-bladder is called physostomous type.
Physoclistous condition: In this condition the ductus pneumaticus is either closed or atrophied. This type of swim- bladder is observed in spiny-rayed fishes.
GAS SECRETING COMPLEX  In all the fishes (physostomi and physoclisti) the anterior part of the bladder is specialised for gas secretion.  In physoclistic species, absorption of gas takes place in the posterior region of the bladder.  In more specialised species as the mugil, gadus and balistes, the posterior part of the bladder is modified into a ‘oval’ for gas absorption.  Its opening is guarded by sphincter muscles.  A small part of the anterior region becomes specialised for secreting gas, and is called the ‘red body’ or ‘red gland’.
FUNCTIONS OF SWIM BLADDER  The swim bladder performs anyone or more of the following functions:  Respiratory function  In a number of primitive teleostomes such as polypterus, lepidosteus and amia, the gas bladder has a lung-like structure and is highly vascular.  In the dipnoi the bladder resembles closely with the lung of amphibians.  In some species as perca fluviatilis, cyprinus, the swim bladder is used to store oxygen; which is available to the fish during emergancy.
 This function is more important in deep sea fishes in which the amount of oxygen stored is pretty high.  Sound production  Swim bladder is an important organ for producing sound in fishes.  It acts as a resonator for the sound produced by other organs, as in Ballistidae and Triglidae.  In some species as the sciaenidae and in the toadfish, sound is produced by the vibration of the bladder wall, caused by the action of muscles attached to it.
 Auditory function  Air bladder is connected with the membranous labyrinth in several species either directly or through weberian ossicles.  In these fishes, the bladder serves to transmit sound waves to the ear more efficiently than in other.  Sensory function  The swim bladder works as a pressure receptor like a manometer or a barometer.  When the fish moves from the depth to another, change in pressure causes compression or rarefaction of gas in the bladder, leading to the deformation of its wall.
 As a hydrostatic organ  The gas bladder is an important hydrostatic organ and makes the fish weightless enabling it to maintain itself in equilibrium with very little effort and without loss of energy.  The swim bladder acts as a float for the fish.  This explains why bottom living species have lost the bladder.  The volume of the bladder is about 5% of the total volume of the fish in marine species, and is about 7-10% in fresh water forms.
CONCLUSION  The air-bladder in fishes varies greatly in structure, shape and size. It is essentially a tough sac-like structure with an overlying capillary network.  The air-bladder may be composed of one or two or many chambers.  It serves as an important organ as it helps in respiration, buoyancy, sound production, audition and sensing.
REFERENCE  A textbook of fish biology and fisheries by S.S. KHANNA and H.R. SINGH
Swim bladder general organization and circulation and function