1. Reading Assignment: • Chapter 16--Relict Bony Fishes end

2. Passive processes: • Diffusion, osmosis, pressure, & 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

3. Definitions: • Ionic Regulation: maintenance of concentrations of specific ions • Osmoregulation: maintenance of constant concentrations of total dissolved substances in extracellular fluids end

4. 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

5. 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

6. 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

7. active passive Saltwater teleosts: H2O drink Na+, Cl- Na+, Cl- Mg++, SO4= Na+, Cl- Mg++, SO4= kidneys chloride cells end

8. active passive pavement cell PC accessory cell PC Cl- Na+ Cl- Cl- Na+ Na+ Na+, Cl- carrier pump gut chloride cell ion channel Chloride Cell fig 6.2: sea water charge charge + 2Cl- Na+ Na+ K+ ATPase Na+,K+ K+ mitochondria internal (blood) tubular system end

9. 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

10. active passive H2O don’t drink Na+, Cl- Na+, Cl- water Freshwater teleosts: Ion exchange pumps; beta chloride cells kidneys end

11. Na+ NH4+ or H+ Cl- HCO3- gill membrane Ion Exchange Mechanisms freshwater interior Na+? active pump ATP Cl-? active pump ATP end

12. Freezing Resistance: • What fishes might face freezing? hagfishes? isotonic marine elasmobranchs? isotonic freshwater teleosts? hypertonic marine teleosts? hypotonic end

13. { rich in alanine Solution for cold-adapted marine teleosts: • Macromolecular antifreeze compounds • peptides (protein) • glycopeptides (carbohydrate/protein) • molecules adsorb to ice crystal surface • interfere with ice crystal growth • ice ruptures cells; interferes with osmotic balance end

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15. Growth: • Longevity • unconfirmed reports of carp 200-400 yr. • authenticated records for carp 50 yr. • large fish-few > 12-20 yr. • some marine spp > 100 yr. thornyspines, orange roughy • many small spp-2 yr. or less (sardines, anchovies) Note: aging with scales, bones, otoliths end

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18. Growth: Other Generalities • females often larger than males • growth rate varies with temp. • longevity inversely proportional to temp. • stress reduces growth • dominance hierarchies - dominant get food • overcrowding can lead to stunting • indeterminate growth - grow throughout life • growth highly variable - can loose weight end

19. Bioenergetic Definition of Growth • energy accumulation (calories) vs. length or weight end

20. Bioenergetics continued: • Energy Budget: I = M + G + E where: I = ingested energy M = energy expended for metabolism G = energy stored as growth E = energy lost to environment end

21. heat G M Bioenergetic Energy Budget: I E end

22. Bioenergetics continued: Ex: M = energy for body repair maintenance activity digestion end

23. Bioenergetics continued: Ex: E = energy in feces ammonia, or urea mucus epidermal cells end

24. Terms: • Standard Metabolic Rate • maintenance met.; no growth, no activity • Routine Metabolic Rate • typical met.; routine growth & activity • Active Metabolic Rate • max. aerobic metabolism end

25. { Factors Affecting Growth: Temperature routine active standard scope Metabolic Rate activity growth Where would growth be best? Temperature end

26. Factors Affecting Growth: Temperature normal O2 reduced O2 Metabolic Rate reduced scope reduced growth Temperature end

27. Growth will not occur at low O2 Ex: LMB cease growing below 5 mg/L end

28. O2 regulator (most species) O2 conformer 0 8 4 Factors Affecting Growth: Dissolved oxygen Routine Metabolism critical O2 concentration Dissolved Oxygen mg/L end

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30. 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

31. water substance end

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