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

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 coelacanth

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

Sensory Systems 1.vision 2.hearing – inner ear; swim bladder amplifies in some fish 3.olfaction – olfactory sacs; taste buds 4.lateral lines of fish – detect vibrations in the water 5.ampullae of Lorenzini (sharks and rays) – sensitive to electric currents 6.geomagnetic sensory system (long distance migration- tuna)

Migration 1.Anadromous- salmon a)can return to the same stream in which they hatched b)may use land features, currents, salinity, temperature, the sun or magnetic field to get close to land c)sense of smell d)die after spawning e)young return to the sea 2. catadromous –freshwater eels 3. Extensive migration-anatomical basis for magnetotaxis -- magnitite