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Homeostasis: Homeostasis: Osmoregulation in Osmoregulation in
elasmobranchselasmobranchs
The difference between The difference between marine, eurahyline and marine, eurahyline and
fresh water speciesfresh water species
OsmoregulationOsmoregulation
• Relationship between solute to solvent Relationship between solute to solvent concentrations of internal body fluidsconcentrations of internal body fluids
• The environment the organism lives The environment the organism lives inin
• Isotonic? Isotonic?
• Hypertonic? Hypertonic?
• Hypotonic?Hypotonic?
Osmolarity = solute/solvent concentrationOsmolarity = solute/solvent concentration
water molecules protein molecules
semipermeable membranebetween two compartments
Fig. 5-20, p.86
2% sucrose solution
1 liter of distilled water
1 liter of 10% sucrose
solution
1 liter of 2% sucrose
solution
HypotonicConditions
HypertonicConditions
IsotonicConditions
Fig. 5-21, p.87
first compartment
second compartment
hypertonicsolution
membrane permeableto water but not to solutions
fluid volumerises in secondcompartment
hypotonicsolution
Fig. 5-22, p.87
Stepped ArtStepped Art
HypotonicSolution
membrane permeable towater but not to solutes
HypertonicSolution
Fig. 5-22, p.87
The Challenge• Avoid desiccation in an aqueous Avoid desiccation in an aqueous
environmentenvironment
– MARINE ANIMALSMARINE ANIMALS• DehydrationDehydration• Elimination of excess saltElimination of excess salt
– FRESHWATER ANIMALSFRESHWATER ANIMALS• Conserve saltsConserve salts
• Eliminate excess waterEliminate excess water
Environmental challenges of Environmental challenges of elasmobranchselasmobranchs• All ureotelic and ureosmotic except All ureotelic and ureosmotic except
potamytrygonid rayspotamytrygonid rays• Marine elasmobranchs surrounded by salt; Marine elasmobranchs surrounded by salt;
lose water; lose water; – need to get rid of excess organic and inorganic need to get rid of excess organic and inorganic
compoundscompounds• Euryhaline species environment fluctuatesEuryhaline species environment fluctuates
– Must handle salt and fresh conditions Must handle salt and fresh conditions • Freshwater speciesFreshwater species
– lose salt and electrolytes; need to get rid of lose salt and electrolytes; need to get rid of excess waterexcess water
Dealing with Environment
• Marine : Maintain serum osmolarity = or Marine : Maintain serum osmolarity = or greater than seawater primarily w/ ureagreater than seawater primarily w/ urea– Little osmotic loss of waterLittle osmotic loss of water
• Dilute Seawater or Freshwater: Serum Dilute Seawater or Freshwater: Serum osmolarity reducedosmolarity reduced– Little diffusion of water inwardLittle diffusion of water inward
Players in osmoregulation Players in osmoregulation
• OrgansOrgans– Kidney, liver, gills, rectal glandKidney, liver, gills, rectal gland
• Organic compoundsOrganic compounds– UreaUrea– TMAO trimethylamine oxideTMAO trimethylamine oxide
• Inorganic ionsInorganic ions– SodiumSodium– ChlorideChloride– Other saltsOther salts
Umanitoba - Gary Anderson
Body FluidBody FluidMarine ElasmobranchsMarine Elasmobranchs
• Reabsorb & retain urea and other Reabsorb & retain urea and other body fluid solutes in tissuesbody fluid solutes in tissues
- Serum osmolarity remains just Serum osmolarity remains just greater than external seawater greater than external seawater (hyperosmotic)(hyperosmotic)
- Don’t have to drink water like Don’t have to drink water like teleoststeleosts
- Water gained excreted by kidneysWater gained excreted by kidneys• Tri-MethylAmine Oxide (TMAO): Acts to Tri-MethylAmine Oxide (TMAO): Acts to counteract the perturbing effects of ureacounteract the perturbing effects of urea
Marine elasmobranchsMarine elasmobranchsPlasma solutes and Plasma solutes and osmoregulationosmoregulation• Different than marine teleostsDifferent than marine teleosts• Have high osmolarityHave high osmolarity• Reabsorb and retain high levels of urea and TMAO Reabsorb and retain high levels of urea and TMAO
in their body fluidsin their body fluids• Osmolarity remains hyperosmotic to surrounding Osmolarity remains hyperosmotic to surrounding
seawaterseawater• TMAO to stabilize proteins and activate enzymesTMAO to stabilize proteins and activate enzymes• Water gained across gills is excreted by kidneysWater gained across gills is excreted by kidneys• Any salt gained across gills is excreted by rectal Any salt gained across gills is excreted by rectal
gland and kidneygland and kidney
Body fluid of euryhaline Body fluid of euryhaline elasmobranchselasmobranchs
• Ammonotelic in frehwaterAmmonotelic in frehwater• As salinity increasesAs salinity increases
– Increase urea production and retention Increase urea production and retention – Decrease urea excretionDecrease urea excretion– Increase Na+ and Cl- Increase Na+ and Cl- – Decrease ammonia excretionDecrease ammonia excretion
• Can not produce and retain as much urea Can not produce and retain as much urea as marine spp. (lower osmolarity)as marine spp. (lower osmolarity)
• Ex. Ex. D. sabina and H. signifierD. sabina and H. signifier
Body fluid of euryhaline Body fluid of euryhaline elasmobranchselasmobranchs
As salinity decreasesAs salinity decreases• Lower osmolarity (less urea and TMAO) Lower osmolarity (less urea and TMAO)
than marine speciesthan marine species• Decrease amount of urea produced and Decrease amount of urea produced and
reabsorbedreabsorbed• Increased urinary excretionIncreased urinary excretion• Loss of sodium and chloride balanced by Loss of sodium and chloride balanced by
electrolyte uptake at the gills and electrolyte uptake at the gills and reabsorbed by kidneys reabsorbed by kidneys
Bull Shark - Bull Shark - Carcharhinus Carcharhinus leucasleucas
Eeigen Werk
Body FluidFresh Water Elasmobranchs
• Lost ability to synthesize and retain urea or Lost ability to synthesize and retain urea or TMAO TMAO
• Body fluid solute concentrations relatively lowBody fluid solute concentrations relatively low
• Freshwater rays abandoned renal Freshwater rays abandoned renal reabsorptionreabsorption- Urine is diluteUrine is dilute- AmmonotelicAmmonotelic
- Ex. Ex. Potamotrygon Potamotrygon raysrays
PotamotrygonidaePotamotrygonidae
Raimond Spekking
Urea- production, retention Urea- production, retention and reabsorptionand reabsorption
• Urea productionUrea production– Occurs in the liverOccurs in the liver
• RetentionRetention– In gillsIn gills
• ReabsorptionReabsorption– In kidneysIn kidneys
Urea production in liverUrea production in liver
Ornithine-urea cycle (OUC)Ornithine-urea cycle (OUC)– Glutamine synthetase is crucial enzyme Glutamine synthetase is crucial enzyme
needed for urea productionneeded for urea production– Euryhaline spp. decrease production of urea Euryhaline spp. decrease production of urea
when entering fresh waterwhen entering fresh water– Freshwater rays lack the enzyme for the Freshwater rays lack the enzyme for the
biosynthesis to occurbiosynthesis to occur– Unsure if urea is produced in other locationsUnsure if urea is produced in other locations– Bacteria hypothesized for being responsibleBacteria hypothesized for being responsible
Marine gills retain ureaMarine gills retain urea
• Do not lose much urea across gills Do not lose much urea across gills • Gill’s basolateral membrane has high Gill’s basolateral membrane has high
cholesterol to phospholipid ratio levelscholesterol to phospholipid ratio levels– Membrane limit diffusionMembrane limit diffusion
• Active transport of urea by Na+/ urea Active transport of urea by Na+/ urea antiporter energized by Na+/K+ antiporter energized by Na+/K+ ATPasesATPases
• Used more for salt regulation and Used more for salt regulation and acid/base balanceacid/base balance
Kidneys reabsorb ureaKidneys reabsorb urea
• Reabsorption contributes to high urea levelsReabsorption contributes to high urea levels• Minor site of urea lossMinor site of urea loss• Thought to involve active transportThought to involve active transport• Use urea-sodium pumpUse urea-sodium pump• Proven in Proven in R. erinaceaR. erinacea• Second hypothesis for passive transport that has Second hypothesis for passive transport that has
not been provennot been proven• Euryhaline spp. decrease renal reabsorption of Euryhaline spp. decrease renal reabsorption of
urea as enter areas of decreased salinityurea as enter areas of decreased salinity– Increases rate of urine flow to rid system of excess ureaIncreases rate of urine flow to rid system of excess urea
Salt regulationSalt regulation
• Rectal gland secretionsRectal gland secretions– Marine spp. surrounded by high salinity Marine spp. surrounded by high salinity – Rectal gland secretes sodium and Rectal gland secretes sodium and
chloridechloride– Na+/ K+ ATPases used Na+/ K+ ATPases used
Osmoregulation by the Osmoregulation by the Rectal GlandRectal Gland
• Rectal Gland = Salt secreting Rectal Gland = Salt secreting mechanismmechanism– Migratory elasmos - regressive rectal Migratory elasmos - regressive rectal
glandgland– Non-functional in freshwater raysNon-functional in freshwater rays
http://fig.cox.miami.edu/~cmallery/150/physiol/rectal.htm
Salt regulation Salt regulation
• GillsGills– Salt uptakeSalt uptake
•Na+/ K+ ATPases even higher in freshwaterNa+/ K+ ATPases even higher in freshwater
– Acid/ base balanceAcid/ base balance•Secrete acidSecrete acid
•H+ excreted/exchanged for Na+H+ excreted/exchanged for Na+
•Run by Na+/ K+ ATPases Run by Na+/ K+ ATPases
– Responsible for ammmonia secretionResponsible for ammmonia secretion
Salt regulationSalt regulation
• Kidney salt excretionKidney salt excretion– Dilute environmentDilute environment
•Urine flow increaseUrine flow increase
– SaltwaterSaltwater•Not solely responsible for salt secretionNot solely responsible for salt secretion
Endocrine Regulation to Endocrine Regulation to Regulate Body Fluid Volume Regulate Body Fluid Volume
and Solute Concentrationand Solute Concentration• CNP - Released from heart CNP - Released from heart
– Increase urine productionIncrease urine production– Stimulate salt secretion from rectal glandStimulate salt secretion from rectal gland– Inhibit drinking and relax blood vessels Inhibit drinking and relax blood vessels
• AVT AVT – Increase in plasma osmolalityIncrease in plasma osmolality– Reduces urine productionReduces urine production
• RASRAS– Antagonistic to CNP, reduces urine flowAntagonistic to CNP, reduces urine flow– Increases drinking Increases drinking – Constricts blood vesselsConstricts blood vessels
Feeding and osmoregulationFeeding and osmoregulation
• Urea is metabolically expensiveUrea is metabolically expensive– 5 umol ATP for 1 mole urea5 umol ATP for 1 mole urea
• Protein in food is main source of N in Protein in food is main source of N in ureaurea
• Elasmobranches must get adequate Elasmobranches must get adequate food to produce the ureafood to produce the urea
• Why ureotelic and not Why ureotelic and not ammonotelic???ammonotelic???
Literture citedLiterture cited
• Hammerschlag Hammerschlag N.2006. N.2006. Osmoregulation in elasmobranches: a review for fish Osmoregulation in elasmobranches: a review for fish biologists, biologists, behaviorists and ecologistsbehaviorists and ecologists. MARINE AND FRESHWATER MARINE AND FRESHWATER BEHAVIOUR AND BEHAVIOUR AND PHYSIOLOGY 39 (3): 209-228 PHYSIOLOGY 39 (3): 209-228
• Speers-Roesch B, Ip YK, Ballantyne JS.2006. Metabolic organization of freshwater, Speers-Roesch B, Ip YK, Ballantyne JS.2006. Metabolic organization of freshwater, euryhaline, and marine elasmobraches: implications for the evolution of euryhaline, and marine elasmobraches: implications for the evolution of
energy energy metabolism inmetabolism in sharks andsharks and rays. JOURNAL OF EXPERIMENTAL BIOLOGY 209 rays. JOURNAL OF EXPERIMENTAL BIOLOGY 209 (13): 2495-(13): 2495- 2508 2508
•Pillans RD, Anderson WG, Good JP, et al.2006. Plasma and erythrocyte solute Pillans RD, Anderson WG, Good JP, et al.2006. Plasma and erythrocyte solute properties of properties of juvenile bull sharks, Carcharhinus leucas, acutely exposed to juvenile bull sharks, Carcharhinus leucas, acutely exposed to increasing environmental increasing environmental salinity. salinity.
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY 331 (2): 145-JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY 331 (2): 145-157 157
• Pillans RD, Good JP, Anderson WG, et al. 2005.Freshwater to seawater acclimation of Pillans RD, Good JP, Anderson WG, et al. 2005.Freshwater to seawater acclimation of juvenile bull juvenile bull sharks (Carcharhinus leucas): plasma osmolytes and Na+/K+ sharks (Carcharhinus leucas): plasma osmolytes and Na+/K+ ATPase activity in gill, rectal ATPase activity in gill, rectal gland, kidney and intestine. JOURNAL OF gland, kidney and intestine. JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY 175 (1): 37-44PHYSIOLOGY 175 (1): 37-44
Literature citedLiterature cited
• Pillans RD, Franklin CE.2004. Plasma Pillans RD, Franklin CE.2004. Plasma osmolyte concentrations and rectal osmolyte concentrations and rectal gland mass of bull sharks gland mass of bull sharks
Carcharhinus Carcharhinus leucas, captured leucas, captured along a salinity along a salinity gradient. gradient. COMPARATIVE COMPARATIVE BIOCHEMISTRY AND BIOCHEMISTRY AND PHYSIOLOGY A-PHYSIOLOGY A- MOLECULAR & MOLECULAR & INTEGRATIVE INTEGRATIVE PHYSIOLOGY 138 (3): PHYSIOLOGY 138 (3): 363-363-