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 gills heat rete mirabile end

Counter-current blood flow Distance along capillaries (rete) Temperature 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) Temperature low high Hypothetical Co-current blood flow: from gills from body arterial blood venous blood counter-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

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Osmosis: water substance semipermeable membrane osmosis end

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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

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 SO 4 = advantages and disadvantages? Examples: saltwater teleosts end

Saltwater teleosts: drink active passive Na +, Cl - Mg ++, SO 4 = H2OH2O Na +, Cl - chloride cells Mg ++, SO 4 = kidneys end

Chloride Cell fig 6.2 : pavement cell PC active passive chloride cell accessory cell sea water internal mitochondria tubular system Na + K+K+ Na + K + ATPase Na +, Cl - Na + Cl - gut carrier 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 H2OH2O Na +, Cl - don’t drink water kidneys Ion exchange pumps; beta chloride cells end

Ion Exchange Mechanisms gill membrane freshwater interior active pump active pump Na + Cl - NH + or H + HCO 3 - ATP end

pO 2 Distance along capillaries efferent Counter-current flow afferent O2O2 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

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substance water end

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