Respiration

1. Respiration

2. Jawless Fishes • Gills - pore-like openings • 7 pairs of gill pouches in lamprey • 5-15 pairs of gill pouches in hagfish, but varying numbers of openings (as few as one/side)

3. Hagfish gills • Gill pouches connect directly to pharynx • Two gills in each pouch • May or may not open directly to outside (depending on species) • May play role in digestion/nutrient absorption

4. Lampreys • Problems with respiration during feeding - no water via pharynx • Developed separate canal to carry respiratory water - from pore on head to gill pouches

5. Lamprey gills • Two gills per pouch • Each pouch has separate exit pore to outside

6. Gills in Chondricthyes and Osteichthyes • Gill filaments attached to posterior sides of bony or cartilaginous gill arches • Gill rakers located on anterior sides of arches

7. Class Chondrichthyes • Gills (pairs of them) located in separate chambers leading from pharynx • Chambers separated by septa (tissues) gills are septate • Each has separate gill slit to outside

9. Skates and rays • Skates and rays have ventral gill slits

10. Skates and rays • Spiracle behind each eye - better developed in skates and rays than in sharks • Likely a modified gill slit • Used to take in respiratory water in benthic skates and rays

11. Osteichthyes gills • Respiration via 4 pairs of gills • No individual openings to outside • Gills on each side covered by single, flap-like operculum

12. Branchiostegal rays • Associated with operculum • Allow for expanding volume of mouth, pharynx chambers while keeping opercula closed • Accordian-like action

13. Osteichthyes gills • Each gill is actually a pair of rows of filaments each attached to the same gill arch • Gills not separated by septa - aseptate

14. Aseptate gills

15. Gill Structure

16. Gill fine structure • Filaments are not simple finger-like tissues • Each filament comprised of stacked plates or lamellae • Greatly increases surface area for interaction with water flowing across gills (water flows between lamellae)

17. Dual Respiratory Systems • Some fish have dual respiratory systems • Gills and lungs

18. Gills and lungs • Gills are main respiratory organs • Lungs serve as back-up system when gills no longer capable of providing gas exchange

19. Lungs

20. Lungs • Pouches branch off esophagus • Breathe air at surface or when they remain out of water

21. Paired lungs in lungfish

22. Lungfish lung - left

23. Lungfish lung • Lungs are mostly simple sacs with network of arteries, veins • Only the most intricate have beginnings of internal compartmentalization

24. Lungs • Paired lungs necessary because of alternating wet and dry periods • Become main respiratory organ when gills become useless

25. Lungs in many fish • Lungs are present in many of the more primitive fishes • Lungfish, bichir, gars, bowfin relatives, sturgeons • All have varying connections with esophagus

28. Swim Bladder • Swim bladder probably arose from paired lungs of primitive fish • Lungs were present before swim bladder

29. Other respiratory organs • Mudskippers and European eels can derive significant amounts (10-90%) of oxygen via cutaneous respiration

30. Other respiratory organs • Walking catfishes (Clariidae) use suprabranchial arborescent organs to respire during their “walks” • Bush-like extensions from gills that do not collapse when out of water

31. Other respiratory organs • Mudskippers have folded and highly vascularized interior walls of opercula/gill chambers, diverticula in mouth and pharyngeal cavities (snakeheads also have the latter)

32. Other respiratory organs • Armored catfishes (Loricariidae) use thin-walled stomach for respiration • Loaches (Cobitidae) use middle/posterior portions of digestive tract