Respiration Circulation and Metabolism Circulatory system Gills and

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Respiration, Circulation and Metabolism • Circulatory system • Gills and Oxygen uptake • Thermal

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

Scombridae Bigeye tuna Thunnus obesus

Scombridae Bigeye tuna Thunnus obesus

Deep Scattering Layer: Diel Vertical Migrators

Deep Scattering Layer: Diel Vertical Migrators

Circulatory System

Circulatory System

Properties of Water Related to Exchange of Gases • Water contains 1% O 2

Properties of Water Related to Exchange of Gases • Water contains 1% O 2 by volume, whereas air contains 21% O 2 by volume • Concentration of O 2 dissolved in water varies inversely with temperature and salinity • Salting out effect • High water temperature = Low O 2 concentration • CO 2 is very soluble in water because it undergoes partial disassociation and forms a weak chemical bond with water (H 2 O + CO 2 = H+ + HCO 3 - = H 2 CO 3)

Ventilation and Respiration • Aerobic Respiration O 2 + CH 2 O CO 2

Ventilation and Respiration • Aerobic Respiration O 2 + CH 2 O CO 2 + H 2 O + ENERGY • Ventilation: process of directing oxygenated water through blood capillary beds • Diffusion: Passive transport of O 2 from water across epithelial cells and into the capillaries containing blood CH 2 O Lactate + energy ANAEROBIC RESPIRATION

Lamprey Shark Teleost

Lamprey Shark Teleost

Ventilation: unidirectional flow of water.

Ventilation: unidirectional flow of water.

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

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

Counter current systems • If fluids flowed in same direction exchange would be about

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.

Thermal regulation: control of body temperature Body temperature of animals relative to that of

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

Mechanisms of thermal regulation in fishes • behavioral • physiological (endothermy)

Mechanisms of thermal regulation in fishes • behavioral • physiological (endothermy)

Behavioral thermoregulation

Behavioral thermoregulation

Physiological thermoregulation (endothermy) Lamnidae Mako Isurus oxyrinchus

Physiological thermoregulation (endothermy) Lamnidae Mako Isurus oxyrinchus

Physiological thermoregulation (endothermy) Alopiidae Thresher shark Alopias superciliosus

Physiological thermoregulation (endothermy) Alopiidae Thresher shark Alopias superciliosus

Physiological thermoregulation (endothermy) Scombridae Bigeye tuna Thunnus obesus

Physiological thermoregulation (endothermy) Scombridae Bigeye tuna Thunnus obesus

Forms of Endothermy • Systemic or whole body endothermy – Lamnidae, Alopiidae, Scombridae •

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

Cranial endothermy (“brain heaters”): • Billfishes (Istiophoridae)

Cranial endothermy (“brain heaters”): • Billfishes (Istiophoridae)

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

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

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

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

Atlantic Bluefin tuna (Thunnus thynnus) Block et al. 2002 Muscle Temp = 28 –

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

Scombridae Bigeye tuna Thunnus obesus

Scombridae Bigeye tuna Thunnus obesus

Deep Scattering Layer: Diel Vertical Migrators

Deep Scattering Layer: Diel Vertical Migrators

Structures and functions involved in systemic endothermy • Distribution of blood vessels • Distribution

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)

Distribution of blood vessels Ectotherm Endotherm

Distribution of blood vessels Ectotherm Endotherm

Distribution of red muscle and blood vessels in cross-section Ectotherm Skipjack tuna Red muscle

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

Distribution of red muscle and blood vessels in cross-section Ectotherm Skipjack tuna Red muscle

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

Heat exchanging retia mirabile of tuna.

Heat exchanging retia mirabile of tuna.