physiological thermoregulation few fishes--tunas & lamnid sharks fish are active --generate heat...

Physiological Thermoregulation

• few fishes--tunas & lamnid sharks

• fish are active --generate heat

• rete mirabile for heat exchange & conserv.

• fish are large--low surface area to mass ratio– body surf. area increases as square of length– body mass increases as cube of length

end

Physiological Thermoregulation

body

skin

skingills

heat

rete mirabile

end

Counter-current blood flow

Distance along capillaries (rete)

Tem

pera

ture

low

high

arterial blood

venous blood

heat

from gills

from body

end

Counter Current flow:

• fluid flowing in opposite directions

• exchange of heat or gas perpendicular to flow

• efficiency versus speed

end

Distance along capillaries (rete)

Tem

pera

ture

low

high

Hypothetical Co-current blood flow:

from gills

from body

arterial blood

venous bloodcounter-current

heat

end

Hypothetical Co-Current flow:

• fluid flowing in same direction

• exchange of heat or gas perpendicular to flow

• speed versus efficiency

end

Hydromineral Balance: Life in a solvent

Environmental forces cause movement of water and dissolved substances

versus

Homeostasis--the need to maintain balance of water and dissolved substances in cells and body fluids of organisms

-constant internal environment

end

Environmental forces:• heat--(movement of molecules) energy for

movement

• diffusion--net movement of molecules

• pressure--density of molecules – difference causes or blocks movement

• osmosis--movement of water

• electrochemical forces--attraction & repulsion of molecules based on charge

end

• Environmental forces work together toward equilibrium

• equilibrium-no net movement of molecules

end

Diffusion:

water

substance

diffusion

end

water

end

substance

water

end

substance

end

Osmosis:

water

substance

semipermeable membrane

osmosis

end

substance

water

end

substance

water

end

substance

water

end

• Diffusion--Net movement of molecules from an area of high concentration to an area of low concentration

• Osmosis--Net movement of water across a semipermeable membrane from an area of high concentration to an area of low concentration

end

Electrochemical forces:

• Movement of ions (charged molecules) due to charge

• likes repel--opposites attract

end

Passive processes:

• Diffusion, osmosis & molecular movement from electrochem. Forces are passive processes – require no energy from organism

• Active Processes-those that require organism to expend energy.– needed for homeostasis; to counter some

passive processes

end

Definitions:

• Ionic Regulation: maintenance of concentrations of specific ions

• Osmoregulation: maintenance of constant concentrations of total dissolved substances in extracellular fluids

end

end

Four osmoregulatory strategies in fishes:

1. Isosmotic (nearly isoionic)– essentially no regulation– body fluids same osmotic conc. as environment

advantages and disadvantages?

Examples: many inverts. Hagfishes; only marine spp.

end

Four osmoregulatory strategies in fishes continued:

2. Isosmotic with regulation of specific ions– organic salts stored in extracellular fluids (prim. urea)– Inorganic salt conc. approx. 1/3 seawater– rectal gland secretes Na+ and Cl- in conc close to that of

seawater (active process)

advantages and disadvantages?

Examples: elasmobranchs, coelacanth (marine)

end

Four osmoregulatory strategies in fishes continued:

3. Osmotic & ionic regulation by marine teleosts– ionic conc. Approx 1/3 of seawater– drink copiously to gain water– Chloride cells eliminate Na+ and Cl-

– kidneys eliminate Mg++ and SO4=

advantages and disadvantages?

Examples: saltwater teleosts

end

Saltwater teleosts:

drink

active

passive

Na+, Cl-

Mg++, SO4=

H2O

Na+, Cl-

Na+, Cl-

chloride cells

Mg++, SO4=

kidneys

end

Chloride Cell fig 6.2:

pavementcell PCPC

active

passive

chloride cell

accessory cell

sea water

internalmitochondria

tubular system

Na+

K+ Na+ K+ ATPase

Na+, Cl-

Na+

Cl-

Cl-

Cl-Cl-

gut

carrier

Na+

Na+

Na+

pump

+

end

Four osmoregulatory strategies in fishes continued:

4. Osmotic & ionic regulation by FW teleosts– ionic conc. Approx 1/3 of seawater– don’t drink– Chloride cells fewer, work in reverse – kidneys eliminate excess water; ion loss– ammonia & bicarbonate ion exchange mechanisms

advantages and disadvantages?

Examples: FW teleosts; FW elasmobranchs

end

Freshwater teleosts: active

passive

H2O

Na+, Cl-

Na+, Cl-

don’tdrink

waterkidneys

Ion exchangepumps; beta chloride cells

end

Ion Exchange Mechanisms

gill membrane

freshwater interior

active

pump

active

pump

Na+

Cl-

NH+ or H+

HCO3-

ATP

ATP

end

end

end

end

pO2

Distance along capillaries

efferent

Counter-current flow

afferent

O2

end

Four osmoregulatory strategies in fishes continued:

1. Isosmotic (nearly isoionic)

2. Isosmotic with regulation of specific ions

3. Osmotic & ionic regulation by marine teleosts (continued)

Summary of previously covered strategies:

end

• The following slides are animated with a feature that does not work on powerpoint2000. save for use when 105 gets ppxp

• These will replace the diffusion and osmosis slides above.

end

water

substanceend

water

substanceend

substance

water

end

substance

water

end