Reading Assignment:

• Chapter 16--Relict Bony Fishes

end

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

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 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

internal (blood)mitochondria

tubular system

Na+

K+ Na+ K+ ATPase

Na+, Cl-

Na+,K+

2Cl-

Cl-

Cl-Cl-

gut

carrier

Na+

Na+

Na+

pump

+

endion channel

charge

charge

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-

NH4+ or H+

HCO3-

ATP

ATP

end

Na+?

Cl-?

Freezing Resistance:• What fishes might face freezing?

hagfishes?

isotonic

marine elasmobranchs?

isotonic

freshwater teleosts?

hypertonic

marine teleosts?

hypotonic

end

Solution for cold-adapted marine teleosts:• Macromolecular antifreeze compounds

– peptides (protein)– glycopeptides (carbohydrate/protein){

rich in alanine• molecules adsorb to ice crystal surface• interfere with ice crystal growth• ice ruptures cells; interferes with osmotic balance

end

end

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

end

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

Bioenergetic Definition of Growth

• energy accumulation (calories) vs. length or weight

end

Bioenergetics continued:

• Energy Budget:

I = M + G + Ewhere: I = ingested energy

M = energy expended for metabolism

G = energy stored as growth

E = energy lost to environment

end

G

Bioenergetic Energy Budget:

I

E

M

heat

end

Bioenergetics continued:

Ex: M = energy for body repair

maintenance

activity

digestion

end

Bioenergetics continued:

Ex: E = energy in feces

ammonia, or urea

mucus

epidermal cells

end

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

Factors Affecting Growth: Temperature

Temperature

Met

abol

ic R

ate

standard

activeroutine

scopeactivity

growth{Where would

growth be best?end

Factors Affecting Growth: Temperature

Temperature

Met

abol

ic R

ate

normal O2

reduced O2

reduced scope

reduced growth

end

Growth will not occur at low O2

Ex: LMB cease growing below 5 mg/L

end

Factors Affecting Growth: Dissolved oxygen

Dissolved Oxygen mg/L

Rou

tine

Met

abol

ism

0 84

O2 regulator (most species)

critical O2 concentration

O2 conformer

end

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

water

substance

water

substance

substance

water

substance

water