Post on 18-Dec-2015
Chapter 44
Osmoregulation and Excretion
Fig. 44-2
Selectively permeablemembrane
Net water flow
Hyperosmotic side Hypoosmotic side
Water
Solutes
Osmoregulation- the control of the concentration of body fluids.
Diffusion- movement of substance from an area of greater concentration to an area of lower concentration
Osmosis- diffusion of water through a semipermeable membrane
Adaptation to Marine EnvironmentReducing salt
• Seabird and marine iguana- nasal salt secreting gland
• Sea snake- sublingual gland• Crocodile- lacrimal gland• Fish gills- chloride cells• Shark- rectal gland
Salt Excretion in Birds
Nitrogenous Waste Excretion
• Ammonia- toxic- Excrete directly into water- jellies- Detoxifyurea
• Urea- need lots of water to get rid of• Uric Acid- birds & reptiles
- more costly to produce than urea, but needs less water to be removed
Strategies to remove Nitrogenous Waste
• Osmoconformer: isoosmotic
• Osmoregulator: hyper-, hypo-,
ureoosmotic
• Euryhaline: wide tolerance range
• Stenohaline: narrow tolerance range
Balancing NaCl in Blood
Osmols- total solute concentration in moles of solute/liter of solution
Osmols- total solute concentration in moles of solute/liter of solution
Marine Fish: hypoosmotic
H2O continually leaves body
continually drinks seawater
excretes salt through gills produces small
amts of dilute urine
Less salt than external
environment
Freshwater Fish: hyperosmotic
H2O continually enters body
does not drinks water
produces large amts of dilute urine
More salt than external
environment
Shark and Coelacanth: ureoosmotic
Maintains high levels of urea and TMAO in blood
excretes salt through rectal gland
coelacanth Rana cancrivora
Hagfish: ionosmotic
nonregulator
Seawater concentration = internal concentration
Osmolarity- measure of total solutes(dissolved particles)
Ions FW m osmol/l SW m osmol/lNa+ 1 470 Cl- 1 550Ca++ variable 10 Total 10 1000
Osmolarity in Freshwater and Saltwater
Habitat Na+ Cl- Urea
seawater sw 478 558
hagfish (Myxine) sw 537 542
lamprey fw 120 96
Goldfish (Carassius) fw 115 107
Toadfish (Opsanus) sw 160
Crab-eating frog (Rana) sw 252 227 350
Dogfish sw 287 240 354
freshwater ray fw 150 149 <1
coelacanth sw 197 199 350
Adaptations to Dry Environment
• Many desert animals don’t drink water
• Kangaroo rats lose so little water that they can recover 90% of the loss from metabolic water and gain the remaining 10% in their diet of seeds.
• Also have long loop of Henle
• Most excretory systems produce a filtrate by pressure-filtering body fluids into tubules.
• Flatworms have an excretory system called protonephridia, consisting of a branching network of dead-end tubules.– The flame bulb draws water
and solutes from the interstitial fluid, through the flame bulb, and into the tubule system.
Diverse excretory systems are variations on a tubular theme
• Metanephridia consist of internal openings that collect body fluids from the coelom through a ciliated funnel, the nephrostome, and release the fluid through the nephridiopore.– Found in most annelids, each segment of a
worm has a pair of metanephridia.
• Insects and other terrestrial arthropods have organs called Malpighian tubules that remove nitrogenous wastes and also function in osmoregulation.– These open into the
digestive system and dead-end at tips that are immersed in the hemolymph.
Nephron
Hormonal Control via Negative Feedback
Fig. 18.16Regulation of Aldosterone secretion by renin-angiotensin-aldosterone (RAA) pathway
Moment of Zen