1. Respiratory System
Fish

2. Respiratory efficiency
R = rate of diffusion
R = DA(Δp/d)
D = diffusion constant (of the medium)
Temperature
Density
A = surface area
Δp = partial pressure differential across membrane
d = distance (thickness)

3. Life (respiration) in Water
Initial Problems:
O2 must be dissolved from atmosphere
O2 tension:
20° air at sea level - 210mL/L [O2]
Fresh HOH – 6.6mL/L
Salt HOH – 5.3mL/L

4. Generic Gills External Gills (Larval fish) Internal Gills (Adult fish)
Sites of gas exchange

5. Gills

7. Gills of Elasmobranchs
Branchial pouches
Narrow chambers
Lamellae on Septa
“Septal” Gills

8. (Efferent flow to dorsal aorta)

10. Pump Ventilation in the Dogfish

11. Teleost Gills Operculum Opercular cavity or chamber “aseptal” gills
Countercurrent exchangers

13. Teleost Gills

15. Scanning electron micrograph of a longitudinal cut through a gill filament

16. Elasmobranchs (C and G)and teleosts (D and H

17. % O2 in water
% O2 in gills
% O2 in water
% O2 in gills

18. Accessory Respiratory Organs
Low O2 conditions
Drying pool
Warm, anoxic swamps
Allow for gaining O2 from air
“Bimodal breathers”
Extensions of Gills
Air bladders

19. Examples of gill extensions
Climbing perch, mud eels (perch), Siamese fighting fish, snakeheads, walking catfish, etc.
Gulp air and remain on dry land
Gulps of air – 30 minutes to 3 hours
Remain on dry land for up to 6 months

21. Outpocketings of gill arches
i.e. labyrinth organ, arborescent organs
Climbing Perch
Walking Catfish

22. Swim Bladder

23. Swim bladders and the evolution of lungs
Two main types
Physostomous
Connected to esophagus by pneumatic duct
Physoclistous
Independent of esophagus (no duct)

24. Evolution of Lungs
and Swimbladders