BIOS240 Water and Salt Physiology

What is the difference between an anadromous migratory fish and a catadromous migratory fish?

Anadromous: running upward to breed (salmon). Catadromous: running downward to breed (freshwater eels).

Be familiar with the relationships between the rate of evaporative water loss (EWL) and each both the following: The animals body weight The animals species The animals metabolic rate

Body weight: EWL tends to decrease as size increases. Species: bugs, crabs then mammals and reptiles in decreasing EWL rates. - Pill bugs have highest EWL rates due to small size and poor defenses against EWL. - Crabs and amphibians are both humidifier and have similar EWL. Metabolic rate: Smaller animals have the higher rate of EWL.

Define the following terms:

Changes in salinity are experience by: 1. Migrating animals such as salmon and eels. 2. Animals in coastal areas where water can be brackish (mic of freshwater and seawater). Osmoregulator: Maintain a stable blood osmotic pressure as ambient osmotic pressure rises or falls. Osmoconformer: Permit their blood osmotic pressure to match ambient osmotic pressure. Stenohaline: Species that can only survive in narrow range of ambient salinity. Euryhaline: Species that can tolerate a wide range of ambient salinity.

Know the following in detail for freshwater teleosts, marine teleosts, marine birds, marine lizards, marine turtles, mammals, and marine elasmobranchs. For each, know the ions involved, as well as key physical structures and how they work. 1. Do they osmoregulate? If so, what kind of osmoregulator are they? 2. What is their osmolarity and tonicity to the water in which they live? 3. How do they gain water? 4. How do they lose water? 5. How do they gain ions (sodium, chloride, calcium)? 6. How do they lose ions? 7. Do they produce dilute or concentrated urine? Why?

Freshwater Teleosts: 1. Hyperosmotic regulators. 2. Hyperosmotic to water. 3. Gain water by osmosis and food. 4. Lose water through large amounts of urine. 5. Gain ions via passive dissuasion across gills and food. 6. Lose ions through gills, feces and passive diffusion. 7. Produce dilute urine to maintain as much salt as possible. Marine Teleosts: 1. Hyposmotic regulators. 2. Hyposmotic to seawater. 3. Gain water by drinking lots of seawater. 4. Lose water through small amounts of urine and osmosis. 5. Gain ions by drinking seawater and eating food and diffusion. 6. They lose ions through active secretion (transport) and feces/urine. 7. Produce concentrated urine. Marine Birds: 1. Hyposmotic regulators. 2. - 3. - 4. Lose water through lungs/skin. 5. Gain ions from seawater and diet. 6. Lose ions through concentrated salts from nasal passage and urine. 7. Produces concentrated urine. Marine Lizards: 1. Hyposmotic regulators. 2. - 3. - 4. Lose water through lungs and skin. 5. Gain ions through seawater and diet. 6. Lose ions through urine. 7. Produce concentrated urine. Marine Turtles: 1. Hyposmotic emulator. 2. - 2. - 4. Lose water through lungs and skin. 5. Gain ions through seawater and diet. 6. Lose ions through urne and eyes (salty tears). 7. Produce concentrated urine. Marine Elasmobranchs. 1. Hyperosmotic regulators. 2. Hyperosmotic to water, hypotonic. 3. Gain ions water by osmosis across gills. 4. Lose water in feces and urine. 5. Gain ions through diffusion across gills and from salt and water in food. 6. Lose ions in feces and urine. 7. - Mammals: 1. Hyposmotic regulators. 2. Hyposmotic to water, hypotonic. 3. 4. Lose water across lungs and skin 5. Gain ions from seawater and diet. 6. 7. Produce concentrated urine

What is the difference between humidic and xeric animals? Name some examples of each. What are humans?

Humidic: Require humid, water rich micro environments. Ex: earthworms, slugs, centipedes, most amphibians, crabs. Xeric: capable of living in dry, water-poor habitats. Ex: mammals, birds, reptiles, insects, arachnids, humans. Humans are xeric.

What is the difference between a hyper-isosmotic regulator and a hyper-hyposmotic regulator?

Hyper-isosmotic regulator: Maintain hyper osmotic blood in freshwater (osmoregulate) but conform (become isosmotic) as salinity increases. Typical of freshwater animals that enter brackish water (fresh and seawater). Have mechanisms for hyperosmotic but not hyposmotic. Hyper-hyposmotic regulator: Maintain a stable blood osmotic pressure over a broad range of ambient osmolarities (euryhaline). Have mechanisms for both hyper osmotic and hyposmotic.

Understand the difference between hyper osmotic, hypo osmotic and isosmotic

Hyperosmotic: Animals in freshwater are considered hyper osmotic regulators i.e. they maintain blood osmotic pressure much higher than the freshwater they live in. Freshwater fish have blood about 250-350 most higher than river water. Freshwater animals tend to lose salt by passive diffusion and take up water by osmosis. - 240 micormole Na+ lost by passive diffusion/day, 2.4 mL water gain daily. 3 factors determine the rate of salt loss and water uptake: 1. Magnitude of osmotic gradients - lower than marine. 2. Permeability of outer body covering 10% that of marine decapods. 3. Surface area over which slats and water are exchanged. Hyper osmotic regulators cope by taking up Na+ making dilute urine and reducing permeability. Low integument permeability. - 240 micromole Na+ uptake across gill/day. 3-7& total metabolic cost. - Produce 2.4 mL dilute urine daily with only 2 or 3 micromole Na+. Example: Marine teolosts (blood plasma 300-500 most) in seawater. Have massive water loss. To cope with this water loss they drink seawater. The seawater initially draws the water out of the blood but Na+ and Cl- are then actively transported out of the intestine. Example: Freshwater fish have blood about 250-350 most higher than river water. Hyperosmotic Summary: 1. Hyperosmotic to ambient water. 2. Water uptake by osmosis (gills). 3. Salt loss by diffusion (gills). 4. Large amounts of dilute urine, very hypososmotic to plasma. 5. Active uptake of Na+, Cl- and Ca2+. 6. Salts and water in food (generally do not drink). Hypoosmotic: Less water permeable to offset water loss - due to osmosis. Example: marine reptiles, birds, mammals. Marine teolosts blood plasma (300-500) are hyposmotic to seawater (1000 mOsm) so they are hyposmotic regulators. Drink seawater to cope. Hyposmotic Summary: Salt gain by diffusion. Water loss by osmosis. Salts and water in food. Salts and water in seawater ingested (source of net water gain). Active extrusion of Cl- active or passive outflow of Na+ Small amounts of urine, nearly isosmotic to plasma, rich in Mg2+ and SO42-. Salts and water in feces. - Salt uptake across gills - Massive water loss. - Replace lost water by drinking seawater (often 10-20% body weight/day). Marine teolosts are hyposmotic regulators so they tend to be less water permeable to offset (prevent) water loss but unlike freshwater fish, marine fish still face massive water loss due to osmosis. Marine fish also have blood ion concentrations that lead to ion influx by diffusion (particularly Cl-). To prevent desiccation due to water loss, marine teolosts drink seawater (often 10-20%) of body weight/day). The seawater in the gut initially draws out water of the blood but...Na+ and Cl- are then actively tranported out of the intestine, favoring local osmotic uptake of water, 50-85% of the gut water is taken up. The kidneys take care of secreting excessive divalents (Mg2+ and Ca2+) in concentrated urine. The gills of marine teolosts are responsible for excreting Na+ and Cl- an example of extra renal excretion. Isosmotic: Isosmotic marine invertebrates are relatively permeable to ions and water. Small differences in ion composition are achieved by ion uptake mechanisms and adjustments in the ion composition of isosmotic urine. Example: Jawless hagfish are the only marine teolosts that are isosmotic.

Understand the difference between hypertonic, hypotonic and isotonic

Hypertonic: A hypetonic solution with a high solute concentration, causes shrinkage (crenation) of the red blood cell as water mice out of the cell and into the hypertonic solution. Hypotonic: A hypotonic solution with a low solute concentration results in swelling and lysis (puff) of a red blood cell placed in the solution. Isotonic: An isotonic solution with a concentration of solutes equal to that inside the cell results in a normally shaped red blood cell. Water moves into and out of the cell in equilibrium but there is no net water movement.

Name 3 ways that land animals lose water.

Integumentary water permeability. - Skin, hair, nails, feathers, scales. - Low integumentary permeability due to integumentary lipids which reduces integumentary evaporative water loss is required in xeric animals. Respiratory water loss. Urine.

How is the rate of water loss calculated?

Rate of water loss (mg H2O/hour) = Rate of O2 consumption (mL O2/hour) x Water loss per unit of O2 consumed (mg H2O/mL O2)

How do xeric animals prevent respiratory evaporative water loss?

Respiratory evaporative water loss depends on breathing function and rate of metabolism. Air is cooled by nasal passages. Low integumentary permeability due to integumentary lipids which reduces integumentary evaporative water loss is required in xeric animals.

How does a mammals size affect its urine concentration? its total water turnover?

Smaller mammals are better at concentrating urine than large animals. Small mammals have higher total water turnover than larger mammals. Specialized invaginated respiratory structures and control air flow to minimize unnecessary evaporating beyond needed for gas exchange. As temperature rises, air water saturation increases; air breathed in gains water content from the body. - Colder air = low water content - Humid air = harder to undergo evaporative water loss. Xeric animal have deep-body temperatures but exhales air is cooler in the nasal passages allowing water aded in deep lungs to be recovered. Vaporizing the water, water condenses out, humans leave some water every time they breath out.

When a hyper-hyposmotic fish moves between freshwater and seawater, what changes occur?

Takes in more water and less ions.

How do terrestrial animals minimize urinary water loss? Explain the differences between humidifier and xeric animals.

Terrestrial animals minimize urinary water loss by producing concentrated urine and reducing solute excreted. Humidic animals cannot produce urine more concentrated than their blood. Xeric animal can produce urine more concentrated than their blood.

Describe the chloride cells of marine teleosts in detail. How do these cells work? What proteins are involved? What drives the movement of each ion?

To get rid of all the salt from the seawater that they absorb from their gut they excrete Na+ and Cl- from gill chloride cells. Na+ and Cl- uptake from blood into gill chloride cells, is by an electroneutral, secondary active transport mechanism (the Na+-K+-2Cl- transporter) driven by the Na+ electrochemical gradient set up by the Na+/K+ATPase. The accumulating intracellular Cl- produces an electrochemical gradient favoring passive Cl- diffusion into the seawater on the apical membrane. Na+ excretion appears to be mainly paracellular (between cells) diffusion drawn by the build up of negatively charged Cl- ions on the gill epithelia outer surface. Chloride cells are abundant in marine fish gills, not mitochondrial rich. These cells produce sufficient ATP for many Na+/K+ATPase that set up the electrochemical gradient required fro transport via the Na+-K+-2Cl- transporter. Salt and osmoregulation takes 8-17% of resting metabolic rate in marine teleosts.