1. Respiration, Circulation and Metabolism
Circulatory system
Gills and Oxygen uptake
Thermal regulation

2. Scombridae
Bigeye tuna
Thunnus obesus

3. Deep Scattering Layer:
Diel Vertical Migrators

4. Circulatory System

7. Properties of Water Related to Exchange of Gases
Water contains 1% O2 by volume, whereas air contains 21% O2 by volume
Concentration of O2 dissolved in water varies inversely with temperature and salinity
Salting out effect
High water temperature = Low O2 concentration
CO2 is very soluble in water because it undergoes partial disassociation and forms a weak chemical bond with water (H2O + CO2 = H+ + HCO3- = H2CO3)

8. Ventilation and Respiration
Aerobic Respiration
O2 + CH2O  CO2 + H2O + ENERGY
Ventilation: process of directing oxygenated water through blood capillary beds
Diffusion: Passive transport of O2 from water across epithelial cells and into the capillaries containing blood
CH2O  Lactate + energy ANAEROBIC RESPIRATION

9. Lamprey
Shark
Teleost

10. Ventilation: unidirectional flow of water.

11. Gill Lamella
Counter current flow between blood and water maximizes exchange between fluids.

12. Counter current systems
If fluids flowed in same direction exchange would be about 50%, regardless the length of the flow systems.
With counter current flow exchange is more complete and varies directly with length of the flow systems.

14. Thermal regulation: control of body temperature
Body temperature of animals relative to that of the environment
Poikilotherms
Homeotherms
Source of animal’s body heat
Ectotherms
Endotherms

15. Mechanisms of thermal regulation in fishes
behavioral
physiological (endothermy)

16. Behavioral thermoregulation

17. Physiological thermoregulation (endothermy)
Lamnidae
Mako
Isurus oxyrinchus

18. Physiological thermoregulation (endothermy)
Alopiidae
Thresher shark
Alopias superciliosus

19. Physiological thermoregulation (endothermy)
Scombridae
Bigeye tuna
Thunnus obesus

20. Forms of Endothermy Systemic or whole body endothermy
Lamnidae, Alopiidae, Scombridae
Regional endothermy refers to maintaining elevated temperatures only in certain parts of the body:
cranial endothermy (“brain heaters”)
Istiophoridae, Xiphiidae

21. Cranial endothermy
(“brain heaters”):
Billfishes (Istiophoridae)

22. Cranial endothermy (“brain heaters”):
Xiphiidae
Swordfish
Xiphias gladius

23. Systemic (whole body) endothermy
Shared presence of:
streamlined body
narrow caudal peduncle
crescent-shaped caudal fin

24. Atlantic Bluefin tuna (Thunnus thynnus)
Block et al. 2002
Muscle Temp = 28 – 30 oC / Water temperature = - 20 oC

25. Scombridae
Bigeye tuna
Thunnus obesus

26. Deep Scattering Layer:
Diel Vertical Migrators

27. Structures and functions involved in systemic endothermy
Distribution of blood vessels
Distribution of red muscle (used for sustained swimming, heat generating)
Rete mirabile (heat exchanger)

28. Distribution of blood vessels
Ectotherm
Endotherm

29. Distribution of red muscle and blood vessels in cross-section
Bluefin tuna
Ectotherm
Red
muscle
Mako shark
Skipjack tuna

31. Distribution of red muscle and blood vessels in cross-section
Bluefin tuna
Ectotherm
Red
muscle
Mako shark
Skipjack tuna

33. Heat exchanging retia mirabile of tuna.