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Osmoregulation = keeping water and salt balanced in the body
Question 1: why is this important Come up with three reasons Question 2: What water and salt problems do the following organisms face? Freshwater fish Marine fish Marine birds Marine mammals Question 3: How might each group solve those problems? Start Lecture with: Osmoregulation = keeping water and salts balanced in your body Question 1: why is this important? Question 2: what problems do_____________f ace? freshwater fish; marine fish; marine birds; marine mammals? Question 3: How might each of these groups solve that problem?
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Definitions Solute Solvent Osmosis Osmotic Pressure Osmolarity
Hyperosmotic Hypoosmotic Osmoconformer Osmoregulator
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Solutes are dissolved particles in solution (any type)
Osmotic pressure: the pressure of water to enter, given the solute concentration --depends on the number of solutes/unit volume (rather than chemical nature of solutes)
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Osmotic pressure: the pressure of water to enter, given the solute concentration
isosmotic (osmotic pressure is equal)
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Osmotic pressure: the pressure of water to enter, given the solute concentration
hypersmotic (higher osmotic pressure) hyposmotic (lower osmotic pressure)
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Water always moves from an area of low osmotic pressure to an area of high osmotic pressure
osmotic pressure: the pressure of water to enter, given the solute concentration Osmosis: movement of water from an Area with lower osmotic pressure to Higher osmotic pressure Hyperosmotic (higher osmotic pressure) Hyposmotic (lower osmotic pressure)
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Osmotic pressures are generally described in osmolar units:
Osmolarity = concentration of solutes in a solution Osmolarity vs. Molarity: 150 mMol sucrose = mOsm sucrose DO OSMOCONFORMERS BEFORE FINISHING INTRO!!!! 150 mMol NaCl = mOsm NaCl
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Definitions Solute: Solvent: Osmosis: Osmotic Pressure: Osmolarity:
Hyperosmotic: Hypoosmotic: Osmoconformer: Osmoregulator: Dissolved particles in a solution What the particles are dissolved in movement of water from an area with lower osmotic pressure to higher osmotic pressure the pressure of water to enter, given the solute concentration Concentration of solutes in a solution Higher osmotic pressure OK, now we are going to go into the three habitats: First: Freshwater (write on side board) (write ‘fish’ underneath it) Lower osmotic pressure Body fluid isoosmotic with envir. Body fluid osmolarity regulated in opposition to environment
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Freshwater teleosts: Osmoregulators
Hyperosmotic to environment Problems? water gain salt loss Solutions? What other freshwater vertebrates do you know? (write ‘frog’ underneath ‘freshwater’) Lots of dilute urine * The gills have specialized cells: CHLORIDE CELLS: they result in the active uptake of ions across the gills move salt into blood
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Main osmoregulatory organ = skin
Amphibians: osmoregulators Hyperosmotic to environment Main osmoregulatory organ = skin Solutions? dilute urine Problems? pump salt into body Gaining water Losing salt …but no gills, so no chloride cells…
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Active transport of salts via skin:
Active transport of Na+ into animal 2 K+ 3 Na+ ATP Cl- OK, so we’ve covered two freshwater vertebrates—what are the two mechanisms? -dilute urine -active uptake of ions across chloride cells or skin Marine vertebrates: what marine vertebrates can you think of? (write on board under ‘marine’) jawless fish (slime hag) sharks, etc. teleosts sea snake turtles marine iguana sea birds (gull, penguin, cormorant) marine mammals These animals can be grouped into ~5 different categories of adaptations To start with, let’s look at the following graph Cl- follows passively (electric gradient)
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Marine Strategies Cl- Na+ Cartilaginous fish osmoconformers
osmoregulator ionoconformer ionoregulator Cl- Na+ Why would you add UREA to your blood? it increases osmolarity while allowing for ion concentrations to be closer to what cells need Which animals are osmnoconformers? Osmoregulators? What about ionoconformers? (ionic composition the same as seawater) Ionoregulators? OK, so jawless fish are osmo and iono conformers (blood like seawater) they are conformers Sharks, etc., ionoregulate, but avoid excess water loss by adding another solute to their blood: UREA Teleosts are regulators…let’s see how they do it Cartilaginous fish
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Marine teleosts: Osmoregulators How? Problems? salt gain Solutions?
(hyposmotic to environment) Problems? water loss salt gain Solutions? gain water (food, drink) So, teleosts use chloride cells pumping salt OUT of the body What’s next? All the marine reptiles and birds fall in the same category produce little urine (isosmotic to plasma) Chloride Cells in the gills! Actively pump ions OUT How? excrete salt …
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Marine reptiles and birds…
Osmoregulators Blood is hyposmotic to seawater Skin is relatively impermeable to salts But still, they are drinking sea water, and eating prey that are primarily osmoconformers (marine inverts) Can’t concentrate urine Can concentrate urine (a *little* bit!)
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Marine reptiles and birds…
How do they get rid of huge salt load? Salt glands! Nasal fluid 5 % salt seawater 3% salt urine 0.3% salt They are eating and drinking high salt
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Salt glands Na+ mOsm seawater 470 sea snake 620 sea turtle 690 Marine Iguana gull cormorant petrel Iguana: nasal cavity Turtle: eye socket Sea snake: mouth Crocodile: tongue birds: on top of skull SO: now on to marine mammals, which are totally different • salt is excreted from the gland to outside the body • more concentrated than sea water! • mechanism is same in marine reptiles -but salt gland is in different places
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Marine Mammals The Mammalian Kidney
Live in seawater…but no chloride cells, no salt glands…? The Mammalian Kidney
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How do mammals make concentrated urine?
Each nephron has a loop of Henle: nephron loop of Henle
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mammalian nephron: Na+ is pumped out of the filtrate
Loop of Henle Na+ is pumped out of the filtrate Results in osmotic gradient in the kidney ECF Why does this matter? 300 600 900 300 mOsm 1200 mOsm 1200 Cortex Na+ Outer Medulla What purpose might this gradient serve? Can water be actively moved? (no) But if there is an abnormally high osmotic pressure outside the nephron, then water can leave by osmosis Inner Medulla
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As filtrate passes through the collecting duct, it loses water to the ECF
Loop of Henle ~150 H2O How concentrated can the filtrate become in this organism? 300 300 Cortex 600 Outer Medulla 600 As concentrated as the ECF The longer the loop of henle, the higher the ECF osmolarity in the Medulla, the greater the concentration of the urine 900 900 Inner Medulla 1200 mOsm
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Final urine is hyperosmotic to plasma
up to 4X in regular terrestrial mammals up to 6X in marine mammals up to 30X in desert mammals!
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Marine Mammals Several Adaptations:
Live in seawater…but no chloride cells, no salt glands…? 1. Long loop of henle in the kidney --concentrated urine --less water lost with waste 2. Diet --carnivores, eating mostly vertebrates --vertebrates have lower osmolarity 3. Absence of sweat glands
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Osmoregulation = aquatic animals
Question 1: why is this important Low solute concentration: cells shrink High solute concentration: cells burst Cells need proper ion balance to function Muscle, nerve cells; Na+/K+ pump Question 2: Problems? Question 3: solutions? Problem: solution Freshwater fish Water gain: produce lots of dilute urine Salt loss: pump salt in through chloride cells in gills Marine fish Osmoconformers: no regulation ionoconformers: increase plasma solutes—Urea Osmoregulators Lose water: drink lots of sea water, produce little urine Gain salt: Chloride Cells in gills Marine birds Gain salt: excrete salt in salt glands Marine mammals Gain salt: excrete hi solute urine Start Lecture with: Osmoregulation = keeping water and salts balanced in your body Question 1: why is this important? Question 2: what problems do_____________f ace? freshwater fish; marine fish; marine birds; marine mammals? Question 3: How might each of these groups solve that problem?
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TERRESTRIAL VERTEBRATES
Total Water gain and loss: = In humans: Water Gain: Food/water intake Metabolic water Water Loss: Excretion Fecal Urinary Evaporative Water Loss Cutaneous Respiratory Reproduction + 2.2 L/day - 1.6 L/day + 0.3 L/day Metabolic water: organic molecules (i.e. glucose) + O2 = CO2 + H2O + ATP O2 needed to collect protons off electron transport chain (glucose-----glycolysis (ATP), citric acid cycle (CO2 and ATP), electron transport chain (H20 and ATP)) Evaporative Water Loss -on land, the struggle is resist water loss to surrounding dry air -permeable body surfaces will lose water to air with less than 95% relative humidity birds and reptiles have more impermeable skin, with layers of dead keratinized cells covering the live epidermis. in reptiles, it’s thickened into scales, in birds, feathers, in mammals, hair an increase in lipids in the skin will decrease evaporative water loss -Every breath you exhale contains 100% water vapor—respiration is a huge site for water loss Environmental factors that can change this equation: (have them come up with these and say why) temperature, wind speed, relative humidity Physiological mechanisms which can alter this equation: high metabolic rate increases metabolic water gain, but also increases respiratory water loss fecal water resorbtion concentrate urine this last is the most common method, and we will spend the rest of the lecture on this. - 0.9 L/day
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Nitrogenous Wastes affect Water Balance
Proteins Nucleic acids Nitrogenous waste products URIC ACID AMMONIA UREA Water soluble Very toxic Excreted w/lots of water Water soluble Low toxicity Excreted w/less water Not water soluble Low toxicity Excreted w/little water
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Excretion Tortoises and Turtles: ammonia urea uric acid Teleost fish
% of urinary nitrogen Species Habitat Ammonia Urea Uric Acid Red-eared slider Freshwater 79 17 4 Forest hinge-back tortoise Moist Terrestrial 6 61 Mediterranean spur-thighed tortoise Dry terrestrial 22 52 Texas tortoise Desert 3 93 ammonia urea uric acid Break down proteins…what’s the waste product? NH3 (ammonia) Why should we care? The form of excretion determines how much water you lose in getting rid of waste products Ammonia: toxic, but soluble in water (many aquatic animals excrete N this way). Urea: not as toxic, but requires water to excrete (some terrestrial animals use this) Uric Acid: insoluble in water, so can be excreted as a paste, but takes much more energy to synthesize than urea (more complex molecular structure). Teleost fish: ammonotelic and ureotelic Elasobranchs: ureotelic Amphibians: All three Mammals: ureotelic Birds and reptiles: uricotelic but, some reptiles can excrete other forms Teleost fish Amphibians reptiles chondrichthyes Teleost fish Amphibians reptiles mammals Amphibians Birds and reptiles
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Mammals: BUT, what about desert mammals?
most drink, eat foods high in water very concentrated urine BUT, what about desert mammals?
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How? How do Kangaroo Rats Cope? Metabolic water:
don’t pant few sweat glands LONG loop of henle Human urine= 1200 mOsm Kangaroo rat = 5500 mOsm eat dry food * don’t drink! don’t tolerate dehydration! How? Metabolic water: C6H12O6 + 6O CO2 + 6H2O 1 g glucose 0.6 g water
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35 g 100g barley Water gains: Water losses: = 60 mL water 60 mL water
54 mL: oxidation water 6 mL: absorbed water 16.1 mL: urine, feces 43.9 mL: evaporation 60 mL water 60 mL water Urine = 9x higher osmolarity than sea water!!
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Terrestrial summary Water in: Water out: Adaptations in the desert?
Food and drink Metabolic water Water out: excretion Evaporative water loss Adaptations in the desert? Extended loop of henle Reduced evaporative water loss (gain in camel nose) High dehydration tolerance
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