1Homeostasis – Chapter 7 - EndocrineEndocrine System - Pituitary – 3 parts;• Neurohypophysis – release chemicals – water loss (vasotocin & isotocin), regulatory (releasing factors effect other parts• Pars intermedia• Adenohypophysis (pars distalis) – prolactin (osmoregulation), Growth, ACTH (release cortisteroids), MSH (color)2Endocrine System• Hypothalamus – controls pituitary• Caudal Neuroendocrine System –Urophysis (caudal end spinal cord) – 2 Urotensins (osmoregulation & steroid)Endocrine System• Thyroid – small cells makes Thyroxin• Interrenal cells = adrenal like cells; Two cell types – chromaffin (epinephrine & norepinephrine) and steroid producing cells (controls metabolism w/ costeroids).• Autonomic Nervous System – poor in agnathans but well developed in teleosts(along either side of spine) – controls involuntary functions3Homeostasis – Chapter 7• Autonomic Nervous System – poor in agnathans but well developed in teleosts(along either side of spine) – controls involuntary functions Homeostasis – Chapter 7• Thermal regulation • Cold blooded vs warm blooded• Poikilotherm vs Homeotherm – fish change temp but water more stable• Ectotherms vs Endotherms - Most = same temperature as water = ectotherms (most fish) v Endotherms (some fish) –temperature vs metabolic rate; eg high metabolic costs4Homeostasis – Chapter 7• Endothermic Fish = Scombrids and Lamnidae (mackeral) & Alopiidae (thresher) Sharks • Heat lost at gills; bring body to external temperature; in tunas etc cooled blood to outside; counter-current; Rete mirabile; blood warmed by muscle activity and heat transferred to cool blood moving to muscles; oxygenated blood is warmed; heat not lost butreturned to muscle.• In thunniform swimming fish – more red cells medial, less heat loss• Also rete mirabile on liver associated w/ gut • Also warm parts of the CNS especially brains and eyes – “regional endothermy”• Eye muscles have lost the ability to contract now produce heat;• Also rete system near eyes;Homeostasis – Chapter 7• Thermal regulation • Acclimation (coping with temperature fluctuations) • Metabolic rate can be dependent or independent on temperature; effects seasonality• Heat Shock Proteins; Alternate enzymes systems (isozymes) vs alternate forms of enzymes from alternate gene forms (allozymes);• Cellular or Tissue level changes -Muscles/heart/liver villi can all change5Homeostasis – Chapter 7• Thermal regulation • High and low temperature (coping with temperature extremes) • Water freezes at 0, seawater at –1.87 but densest at 4 degrees; fish freeze at -.7 so freshwater fish are protected but salt water fish have problem• Supercooled and do not encounter ice crystals• Some = biological antifreeze (glycoproteins)• INCREASE CONCENTRATIONS OF OSMOLYTES;Homeostasis – Chapter 7• Thermal Preferences and habitat selection – select best habitat for growth and reproduction – good link of physiology and behavior/ecology;6Osmoregulation – 4 Strategies• Osmoregulation; Most fish stenohaline (very narrow salt tolerance) but Diadromous (part freshwater part salt) fish (lampreys, salmon, eels) – Euryhaline (wide tolerance for salt)• Anadromy – adults spawn in fresh – juvs to salt• Catadromy – adults spawn at sea, move to fresh and return to sea to spawn• Amphidromy – Spawning either freshwater or saltwaterExamples of Diadromous Fish• Anadromous – Lampreys, sturgeons, herring, salmon, smelts, icefice, gobies, sea catfish, soles, sticklebacks, cods, sculpin• Catadromous – Eels, scorpionfish, galaxiids, temperate basses, snooks, mullets, righteyeflounders• Amphidromous – grayling, whitebaits, galaxiids, herrings, sculpins, sandperches, sleepers, pipefish7Osmoregulation – 4 Strategies• – Four major strategies• (1) Nothing – Hagfish – all marine and stenohaline (tolerate narrow range); Have salt concentration about equal to seawater – only vertebrate to do so.2 – Marine elasmobranches and coelacanths4 – Freshwwaterteleosts3 – Marine Teleosts8Osmoregulation – 4 Strategies• – Four major strategies• (2) Marine elasmobranches and Coelacanths = Inorganic salt concentrations equal about 1/3 seawater (like most verts) – but organic salts (Urea and trimethylamine Oxide TMAO) brings total salt concentration up to seawaterFreshwater vs. Saltwater9Osmoregulation – 4 Strategies• (3) Marine Teleosts – Internal salt concentration = 1/3 sea water – operates Hyposmotically – lose water to diffusion • Replace water by continually drinking then special cells (Chloride cells) in gill filaments & opercular skin epithelia eliminate salt via active transportOsmoregulation – 4 Strategies• Marine Teleosts• 1) Loses water through gills and skin• 2) gains water and salt by drinking• 3) Removes salt via chloride cells• 4) Salt lost via feces• 5) Salt and little water lost via minute urine• 6) Fewer and smaller glomeruli; reabsorb glucose/proteins in convoluted tubules10Osmoregulation – 4 Strategies• (4) Freshwater teleosts and some elasmobranches = Hyperosmotically (blood concgreater than H2O) – they gain water by diffusion.• Well developed kidneys excrete large amounts of dilute urine (.33 body weight per day) –controlled by blood pressure; Salts are taken up primarily through the gills – ions pumped inwards – chloride cellsOsmoregulation – 4 Strategies• Freshwater teleosts• 1) absorb water through gills and skin• 2) obtain salts through “chloride” cells and with food• 3) removes water via copious, dilute urine (5-12% body weight)• Numerous large glomeruli and reabsorbs salts along convoluted tubules11Gill filamentChloride