Fish Swim bladder

1. SCHOOL OF STUDIES IN ZOOLOGY
JIWAJI UNIVERSITY, GWALIOR
Dr. Ramkumar Lodhi
Conservation Biology Lab
TOPIC- SWIM BLADDER GENERAL ORGANIZATION AND CIRCULATION
AND FUNCTION

2. SYNOPSIS
 Introduction
 General organization and circulation
 Types of air bladder
 Gas secreting complex
 Functions of the swim bladder
 Conclusion
 Reference

3. 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.

4. 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.

6. 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.

7. Physoclistous condition:
In this condition the ductus pneumaticus is either closed
or atrophied. This type of swim- bladder is observed in
spiny-rayed fishes.

8. 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’.

9. 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.

10.  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.

11.  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.

12.  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.

13. 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.

14. REFERENCE
 A textbook of fish biology and fisheries by
S.S. KHANNA and H.R. SINGH