Respiration, Circulation and Metabolism

• Circulatory system• Gills and Oxygen uptake• Thermal regulation

ScombridaeBigeye tunaThunnus obesus

Deep Scattering Layer:

Diel Vertical Migrators

Circulatory System

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)

Ventilation and Respiration

• Aerobic RespirationO2 + 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

Lamprey Shark Teleost

Ventilation: unidirectional flow of water.

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

Gill Lamella

•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.

Counter current systems

Thermal regulation: control of body

temperatureBody 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)

Behavioral thermoregulation

LamnidaeMako Isurus oxyrinchus

Physiological thermoregulation (endothermy)

AlopiidaeThresher sharkAlopias superciliosus

Physiological thermoregulation (endothermy)

ScombridaeBigeye tunaThunnus obesus

Physiological thermoregulation (endothermy)

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)

XiphiidaeSwordfishXiphias gladius

Cranial endothermy (“brain heaters”):

Systemic (whole body) endothermy

Shared presence of:streamlined bodynarrow caudal pedunclecrescent-shaped caudal fin

Block et al. 2002

Atlantic Bluefin tuna (Thunnus thynnus)

Muscle Temp = 28 – 30 oC / Water temperature = - 20 oC

ScombridaeBigeye tunaThunnus obesus

Deep Scattering Layer:

Diel Vertical Migrators

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 red muscle and blood vessels in cross-section

Ectotherm Bluefin tuna

Skipjack tuna Mako shark

Red muscle

Distribution of red muscle and blood vessels in cross-section

Ectotherm Bluefin tuna

Skipjack tuna Mako shark

Red muscle

Heat exchanging retia mirabile of tuna.