Gills are primary respiratory organs in fishes, Extra branchial respiration is highly useful for survival when oxygen supplied by gills is not sufficient.

2. ADVISORY COMMITTEE
• Major Advisor
• Major Subject
• Minor Subject
• Major Supporting
• Dean’s PG Nominee
• Dr. Farooz Ahmad Bhat
• Dr. Tasaduq Hussain shah
• Dr. Adnan Abubakr
• Dr. Bilal Ahmad Bhat
• Dr. Aishwani Kumar

3.  Some tropical fishes have evolved special structures called the
accessory air breathing organs.
 These fishes belonging to different families and about 20 genera
possess both gills and some other special organ for breathing
through water as well as air.
 Majority of the teleostean fishes have well developed
gills for respiration which are very efficient organs for
gaseous exchange.

4. The Commonest Air-Breathing Structures
 Skin
 Branchial Epithelium Or Branchial Diverticulam
 Pharyngeal Epithelium Or Pharyngeal Diverticulam
 Air-Filled Branchial Chamber
 Gas bladder And Lung
 Stomach And Intestine

5.  The fishes like Anguilla anguilla, Periophthalmus,
Boleophthalmus habitually leave then water and
migrate through damp vegetation.
 During this period skin become thin, moist,
glandular and richly vascular.
 In Monopterus and Mastacembalus the glandular
secretions of their skin protect them from desiccation
when fishes move out of water or during up of muddy
ponds.
 The Goblet cells become highly active
Cutaneous Respiration By Skin

6. Bucco-Pharyngeal Respiration
 In Periophthalmus, Monopterus (Swamp eel),
Electrophorus Buccal and pharyngeal epithelia
are richly vascular they serve as a respiratory
surface for gas exchange.
 Fish may keep its branchial chamber water
filled ,while going out of water for gill
respiration to continue. pharyngeal epithelia
of Monopterus
Periophthalmus

7.  In some fishes like Dipnoans, polypterus, Amia,
lepidosteus, gymnarchus and Notopterus the air
bladder is used in a manner, similar to amphibian
lung (Urodele condition).
 In certain cases of dipnoi and Gymnarchus, even
the respiratory vein is so modified that it actually
opens into the auricle.

8. • The air bladder of a freshwater teleost,
Notopterus notopterus has a wide pneumatic
duct (physostomous swim bladder) and acts
as an accessory respiratory organ.
• The network of blood capillaries* covered
by a single layer of epithelium facilitates
diffusion of respiratory gases between the
blood and the air contained in the air bladder
(A) Esophagus (B) pneumatic duct (C) physostomous
swim bladder (D) stomach
. *

9. • A: Staining of erythrocytes in an artery (Art) and an adjacent vein.
• B: Rete mirable close to the junction of the pneumatic duct.
• C: Patterns of branching of arteries (Art) and veins.

10. • It develops from branchial epithelium.
• It is located one on each side above the gills.
• Labyrinthine organs have been found in few perches
viz., Anabas testudineus and Trichogaster
fasciatus, Osphronemus, Macropodus , Betta
• These are formed within the extrabranchial
chambers, enclosed between the gills and the
operculum
• Internal wall of the chamber folded into three or
more concentrically arranged laminae.
• These organs are derived from the 1st gill arch.
1st gill arch

11. Arborescent Organs or Dendriform Organs or
opercular lungs
 Two air chambers which develop from dorsal surface of
branchial chamber.
 The air chamber contains two richly vascular branching
structures, called as dendriform organs or arborescent organs.
 The surface of arborescent organs covered by vascular fold of
branchial epithelium .
 The organs provide a respiratory surface for gas exchange.
 Eg: Some cat fish: Clarias, Heterobranchus
Gill: (G) Gill fan: (F) Membrane
covering suprabranchial chamber
(arrow) and Dendritic organ: (DO)

12. Branchial AirTubes
 These are two long lung like air tubes, situated one on each
side of the vertebral column
 They are extension of the branchial chamber and extentend
middle of tail.
 They provides a respiratory surface for gas exchange Eg :
Heteropneustes fossalis
Oral papillae
 In Electrophorus electricus, the gills are degenerate.
 Mucus membrane in its mouth is raised into a large oral
papillae. These are richly supplied with blood capillaries.
These take in oxygen from air gulped into oral cavity.
Vascularised oral papillae
in Electrophorus

13. Pharyngeal Air Sacs
 In Amphionus cuchia (Swamp eel) the gills are
reduced and only second gill arch bears filaments
while the third arch has fleshy vascular membrane.
 The pair of lungs like pharyngeal pouches located on
lateral side of head form air breathing organ in this
species.
 In Amphionos cuchia pharyngeal diverticulum
develops prior to the development of gills this is
because the fry of A. cuchia are hatched out purely in
muddy water
Gill chamber Air sac
Gut wall Gills
Amphinous

14.  In some fishes Air is swallowed and forced back into the elementary canal.
 A part of the canal is modified for aerial respiration.
 Eg. Loaches (Lepidocephalichthys, Misgurnus fossilis), Amarican fishes
belonging to Siluridae & loricaridae.
 The middle and hinder parts of the intestine have been known to serve two
functions, i.e., digestive as well as respiratory in Cobitidae.

16. The membrane lining the air breathing organs of
various species shows a complicated structure. It is
composed of “Respiratory islets” (locally occurring
structures resembling lamella of the gills) and non-
vascular areas called the ‘Lanes’. The islets are highly
vascular and are the sites for gaseous exchange.
They are lamellar in structure in Heteropneustes and
Clarias but form papillae or nodules in Channa and
Amphipnous.
Pillar cells are characteristic of the teleostean gill, are
seen in respiratory epithelium of Clarias and
Heteropneustes.
Pillar cells

18. The accessory air breathing organs in H. fossils are highly specialised and
consist of:
(a) Two air sacs,
(b) Fans
(c) Respiratory membrane.
Air sacs :- one on each side
 Arise from the suprabranchial chamber of the opercular cavity.
 These sacs are thin walled, tubular structures having highly
vascular walls
 Extending upto the middle of the caudal region
 Each air sac receives blood from the 4th afferent brachial vessel
of its own side

20.  Fans: Gill filaments of all the gills are reduced in size and those
of the upper limb of the gill arch are fused to form four `fans',
one on each gill arch.
 The air sac and the 'fans' are the result of fusion and
modification of gill filaments and reduction of the lamellae.
 The fish inhales air which enters the suprabranchial chamber
through the inhalant aperture and is passed into the tubular sac.
After the exchange of gases, used air is expelled through the
external branchial opening, and the fans help in this process.

22. Air breathing organs of Anabas (climbing perch)
consist of:
o Air chamber
o labyrinthine organ on each side
The air chamber lies between the first gill arch and
the Hyomadiular.
The respiratory epithelium lining the air chamber
is highly vascular and may be folded to increase
the surface.

23. A well developed labyrinthine organ is present on the
first gill arch.
- It consists of three concentric bony plates.
- The first fused with the respiratory epithelium of the air
chamber and divides it incompletely into two.
- The second and the third plates are greatly folded due to
which the labyrinthine organ has a complex structure.
The labyrinthine organ is also covered by a vascular
respiratory epithelium, and serves to increase the respiratory
area for exchange of gases.

24. TRICHOGASTER
• In this species air breathing organs consists of:
a. Suprabranchial chamber
b. Labyrinthine organ
c. Respiratory membrane
(As in Anabas )
• A labyrinthine organ has two leaf like
expansions and develops on epibranchial of
ist gill arch.

25. CLARIAS BATRACHUS
 The air breathing organs of Clarias are highly evolved and complex.
these include:-
(i) A suprabranchial chamber on eachside,
(ii) Two beautiful air trees or 'rosettes' on each side,
(iii) The 'fans', and
(iv) The respiratory membrane.

26. Fig. 1: Sharp tooth catfish Clarias gariepinus. Fig. 2: Ventral part of head region with gill (G),
Gill fan (F), Membrane covering suprabranchial chamber (arrow) and dendritic organ (DO).
Fig. 3: gill arches (1, 2, 3, 4 and 5), gill fan (F), small part of dendritic organ (SDO) and large
part of dendritic organ ( LDO). Fig. 4: gill arches (1, 2, 3, 4 and5), gill fan (F), small part of
dendritic organ (SDO) and large part of dendritic organ ( LDO).

27.  The suprabranchial chamber is situated above the gills.
- It is lined by a highly vascular respiratory membrane, and is divided into two cup-life compartments.
 A beautiful 'rosette' or dendritic organ is present in each compartment.
oThe anterior rossete is smaller in size and is borne on the epibranchial of the
second gill arch, while the posterior one is larger and is present on the
epibranchial of the fourth gill arch.
oEach rosette is a highly branched tree-like structure, each branch ending in a
knob. Each knob or bulb has a core of cartilage and is covered over by eight
folds.

28.  Each knob is believed to represent eight shortened and fused gill filaments
 In addition to the rosettes some of the gill filaments of each arch are fused to form a
'fan', so that there ar filaments are reduced in size
 The fish frequently rises to the surface of water and gulps in air, which enters the
suprabranchial chamber through the inhalant aperture which is a narrow slit between
the second and third arch.
 The air entering the opercular cavity is directed into the suprabranchial chamber by the
action of the fans. The slit between the third and the fourth arches is used as the
exhalant aperture, and the air, after gaseous exchange is passed into the opercular cavity
and then to the exterior.

29. MUDSKIPPERS
The mudskipper (Boleopthalmus and Periopthalmus) possess accessory
respiratory organs and breathe through water as well as air.
In addition to the gills, these fishes breathe through skin and pharyngeal and
opercular chamber.
The skin is well adapted and is highly adapted for respiration. The blood vessels
penetrate the dermis and branch into fine capillaries lying below the epithelial
layer.
In Boleophthalmus there are button-shaped papillae on the head, and respiratory
papillae are associated with each scale specially on the dorsal surface.

30. The buccal and the pharyngeal cavities and the
opercular chamber are of large size and can be further
enlarged to retain air.
A dorsal extension of the opercular chamber
(suprabranchial chamber) and a ventral extension
below the gill arches called the inferior branchial
recess are also present in several species of
mudskippers. These are extensively vascularised and
form accessory respiratory organs.
Boleopthalmus
Periopthalmus

31. DIURNAL FLUCTUATIONS IN AERIAL RESPIRATION
 A diurnal fluctuation in the quantity of free carbon dioxide and dissolved oxygen has been
shown to exist in swamps.
 Air breathing fishes exhibit fluctuation in their breathing pattern. These fishes are nocturnal
in habit, and are at rest during the day, and are able to meet their oxygen requirement through
aquatic respiration by gills.
 During night, these fishes become active and need more oxygen, which is in short supply
during night. Hence, these fishes frequently rise to the surface to gulp in air.
 Dissolved oxygen and free Carbon dioxide act as the "steering wheel" controlling the
metabolic activities of the living biota in the swamps.