In aquatic animals such as fish respiration takes place through special respiratory organs called gills, however lung fish respiration takes place through lungs. Gills are present on both the sides of the head of fish. The gills are covered by gill covers also called operculum. When the fish open its mouth, water is drawn into the buccal cavity and passed through the gills. The gills contain special type of cells that absorb the oxygen present in water. The absorbed oxygen is then supplied to all the cells of body through blood. In the cells, oxygen is converted into carbon dioxide and returned back to gills through blood. Ultimately, the gills release the carbon dioxide in water passing through them. Respiration in Fish The gills of fish are very efficient; it is estimated gills can extract about 80% oxygen dissolved in water. In addition to the respiratory organs, the gills have an important role in maintaining the right balance of salts in the body.

1. Presenter Shanza Gul
Presentation topic Respiration in fishes
Presented to Sir Zaigham Hassan
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2. Respiration
 A process involving;
o the production of energy, typically with the intake of
oxygen
o and the release of carbon dioxide from the oxidation
of complex organic substances.
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3. Respiration in fishes
 Fishes are successful group of vertebrates because of;
 Its ability to obtain oxygen from external environment by
means of vascularized gills, lungs, or skin to transport this
oxygen to the tissues and to unload the oxygen to the
tissues.
 In the same manner CO2 are transported in the blood and
eliminated at the gills or other respiratory structures.
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4. Respiration in fishes
 In some scaleless fishes, gas exchanges takes place
with skin.
 In embryos of fishes various tissues serve as
temporary breathing structures like yolk sac.
 After hatching, the developing pectoral fins may assist
the developing gills.
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5. Respiration in fishes
 Temporory opercular vascularization for gas exchange
may also occur as in bowfin fish.
 For taking oxygen directly from air, adaptations are
included in modifications of gills , the mouth cavity , the
intestine and the gas bladder.
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6. Gills in Lampreys
 Petromyzon marinus has seven paired gill sacs.
 Gill sacs opens towards lumen of alimentary tract.
 Each is divided from the next by a thin diaphragm.
 Inside of each gill sac is covered by radially arranged
gill filaments which have small secondary cross folds.
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7. Gills in Lampreys
 50 to 70 contractions/minute of gill pouches found when sea lamprey
(Petromyzon) attached to its prey while 120 to 200 contractions/minute in
river lamprey (Lampetra fluviatilis).
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8. Gills in lampreys
 Respiratory water
 enters the pouches by tidal flow
 expelled through contraction of branchial compressors
muscles
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9. Gills in lampreys
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10. Gills in Lampreys
 Lampreys rarely use suctorial mouth for inspiration.
 The ‘suction cup’ implies that the pressure inequalities due to
breathing are not translated forward into mouth cavity.
 When the rasping tongue is at work, the buccal funnel is closed
posteriorly by the semi annularis muscle and inside openings
of the gill pouches are protected by the velum.
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11. Suction mouth
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12. Gills in Lampreys
 Between the gill pouches , septa are there , containing venous
blood sinuses, cartilaginous supports from branchial basket
and muscles.
 These interbranchial septa receive an afferent artery each
from trunchus arteriosus.
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13. Gills in Lampreys
 Afferent artery divides anterior & posterior branchial-pouch
arteries and further into arteries of filaments.
 Filamental arteries spread into capillaries and lacunae in gill
lamellae where gas exchange occurs.
 Oxygenated blood leaves the lamprey gills, headed towards
dorsal aorta by vessels in septa parallel to afferent pouch
arteries.
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14. Respiration in hag fishes
 The hag fishes have two distinct breathing habits
 When it is not feeding it is buried in mud except the anterior
part so the water reaches the gill pouches from
nasopharyngeal cavity.
 When mouth is buried water flow through
esophageocutaneous duct. this duct open externally
behind the last gill pouch.
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15. Respiration in Sharks and Rays
 5 more rarely 6 or 7 external gill slits exists ventrally each side
in rays (Rajiformes) but laterally in Sharks (Squaliformes).
 An additional anterior openings in both sharks and rays
(Elasmobranchii) is Spiracle, corresponds to vestigial
primitive first gill slit
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16. Spiracle in sharks
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17. Gills in Sharks and Rays
 In sharks, respiratory water typically enters through mouth, but
in rays, the spiracle admits most of water that flows
subsequently over the gills.
 Well developed septa with cartilaginous supports and individual
gill-arch muscles characterize each holobranch; the oral and
aboral sides of septa each carry a hemibranch composed of gill
tissue proper.
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18. Gills in Sharks and Rays
 Both primary & secondary gill filaments present in each
hemibranch.
 The distal end of primary gill filaments are detached from
septum so that two hemibranch in apposition may form an
effective barrier that forces the water to penetrate between all
filaments when it seeks its exit as a result of suction and
pressure of respiratory movements.
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19. Gills of a shark
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20. Gills of sharks
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21. Gills in Sharks and Rays
 Division of Respiratory cycle of Elasmobranchs:
Three consecutive phases;
1. First phase:
 Coraco-hyiod & coraco-branchial muscles contract to widen
the angle enclosed by gill arches and to enlarge the
oropharyngeal cavity, water enters by suction through the
mouth cavity or spiracle.
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22. Gills in Sharks and Rays
 During this phase gill flaps are held to the skin by exterior
water pressure; thus external gill slits are closed.
2. Second phase:
 Abductors of lower jaw and gill arches relax, but adductor
muscles (interarcual adductors) between upper & lower
portion of each gill arch contract and the mouth cavity begins
to function as pressure pump.
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23. Gills in Sharks and Rays
 Contraction of interarcual adductors bulges the oral portion of
interseptal spaces; hydrostatic pressure at the inner gill surfaces is then
reduced and water is drawn into the gill cavities, which are still closed
towards outside.
Third phase:
o Interarcual adductors relax,another set of muscle contracts to narrow
the internal gill clefts, and the water is forced through the gill lamellae.
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24. Respiration in Sharks and Rays
o Then flaps at external gill clefts open passively and allow the
water to flow to outside.
o However many sharks e.g mackerel sharks (Lamnidae) DO
NOT show such pronounced breathing movements and can
only take in sufficient respiratory water while swimming; they
suffocate readily when immobilized by capture or other causes.
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25. Respiration in sharks
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26. References
 Ichthyology (2nd edition) by Lagler, Bardach, Miller, Passino.
 Wikipedia.org & Google images (visuals)
 www.britannica.com
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