Chapter 44 Osmoregulation and Excretion

Fig Selectively permeable membrane 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 Environment Reducing 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 -Detoxify  urea 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

Marine Fish: hypoosmotic H 2 O continually leaves body continually drinks seawater excretes salt through gills produces small amts of dilute urine Less salt than external environment

Freshwater Fish: hyperosmotic H 2 O 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 coelacanthRana cancrivora

Hagfish: ionosmotic nonregulator Seawater concentration = internal concentration

Osmolarity- measure of total solutes(dissolved particles) IonsFW m osmol/l SW m osmol/l Na+1470 Cl-1550 Ca++ variable10 Total Osmolarity in Freshwater and Saltwater

HabitatNa + Cl - Urea seawatersw hagfish (Myxine)sw lampreyfw12096 Goldfish (Carassius)fw Toadfish (Opsanus)sw160 Crab-eating frog (Rana)sw Dogfishsw freshwater rayfw150149<1 coelacanthsw

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 Regulation of Aldosterone secretion by renin-angiotensin- aldosterone (RAA) pathway

Moment of Zen