Respiratory System 1

1. Respiratory System 1 Fish Amphibian

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. Conditions for high R • Large respiratory A • Short d external medium | blood • Flow rates trade-off: Fast flow – gradient replacement Slow flow - diffusion

4. Other important “adjustable” features • Ventilation rates • Amount of respiratory A in use at any one time • What happens if too much A? • Quantity of gas • Properties of medium • Density • Viscosity • Body Size

5. 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

6. Solutions??? • Prefer cooler HOH • + increased solubility of O2 • - loss of body heat • - reduced kinetics • Gills • + increased A Increased R • - increased A • high metabolic costs • Inc. loss of blood nutrients • - high metabolic costs  lots of CO2 High metabolic costs Easily dissolved COO + HOH  H2CO3

7. Generic Gills • External Gills (Larval fish) • Internal Gills (Adult fish) • Primary gill lamellae – Vascularized plates • Secondary gill lamellae – Perpendicular tissues • Sites of gas exchange

8. Gill Development (Elasmobranch)

9. Gills of Lamprey • Blind respiratory tube • Large sacular branchial pouches • Lined with 1° lamellae • “pouched” gills • External gill slits • One-way (not feeding) • Two-way (feeding)

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

11. (Efferent flow to dorsal aorta)

13. Concurrent Flow 2° lamella Lateral Blood Water = = eq Lo O2 Hi CO2 Hi O2 Lo CO2 Medial

14. Countercurrent Flow 2° lamella Lateral Blood Water Lo O2 Hi CO2 Lo O2 Hi CO2 Hi O2 Lo CO2 Hi O2 Lo CO2 Medial

15. Pump Ventilation in the Dogfish

16. Ram Ventilator Shortfin Mako (Isurus oxyrinchus) Pump Ventilator Shortspine Spurdog (Squalus mitsukurii)

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

18. Teleost Gills

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

21. Examples of gill extensions • Climbing perch, mud eels (perch), Siamese fighting fish, snakeheads, walking catfish, etc. • Gulp air and remain on dry land

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

25. Swim Bladder

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

27. Evolution of Lungs and Swimbladders

29. Oxyhemeglobin – acidic conditions for release O2 dumping > O2 uptake Countercurrent multiplier based on blood pH Physoclistous swim bladder operation

30. Amphibians External Gills Become enveloped in Opercular fold Develops from an external opening – “spiracle”