2. Introduction Homeostasis Thermal regulation hormones – endocrine system Enzymes osmoregulatory processes Occasionally marine organisms just “pick up and move” if environmental conditions are unfavorable

3. Definitions Homeostasis = maintaining steady state equilibrium in the internal environment of an organisms Solute homeostasis = maintaining equilibrium with respect to solute (ionic and neutral solutes) concentrations Water homeostasis = maintaining equilibrium with respect to the amount of water retained in the body fluids and tissues

4. Definitions, continued Osmotic concentration Total concentration of all solutes in an aqueous solution measured in units of osmolal osmolals = 1 mole of solute/liter of water milliosmolals = 1/1000th of one osmolal

5. Osmoregulation in different environments Challenge to homeostasis depends on steady state concentration of solutes in the body fluids and tissues as well as concentration of solutes in the external environment marine systems: environment concentration = 34 - 36 parts per thousand salinity = 1000 mosm/l freshwater systems: environment concentration < 3 ppt salinity = 1 - 10 mosm/l Estuaries: vary with tides and precipitation

6. Hypertonic vs Hypotonic

7. Osmoregulatory Strategies Hypoosmotic – saltwater fish Hyperosmotic – freshwater fish Isosmotic: regulation of specific ions Isosmotic: nearly isoionic, osmoconformers

8. Cells swell or shrink

11. Body fluid osmotic concentrations

12. Osmoregulation in different environments Each species has a range of environmental osmotic conditions in which it can function: stenohaline - tolerate a narrow range of salinities in external environment - either marine or freshwater ranges euryhaline - tolerate a wide range of salinities in external environment - fresh to saline short term changes: estuarine - 10 - 32 ppt intertidal - 25 - 40 long term changes: diadromous fishes

13. Salmon migrating from sea to river 300px-Jumping_Salmon fish migration wikipedia

14. Types of Osmoregulators Hyperosmotic regulator Osmoconformer Hypo-osmotic regulator

15. 020040060080010001200 Invertebrates SW Invertebrates FW Sharks SW Sharks FW Teleost Fish SW Teleost Fish FW Amphibia Reptiles, Birds, Mammals Body Fluid, mOsm/Kg IonsUrea & TMAO Seawater Brackish water Fresh water Osmoregulators and osmosconformers

17. Osmoregulation Marine fish face two problems: they tend to lose water and gain ions.

18. Osmoregulation Freshwater fish face two problems: they tend to lose ions and gain water.

19. Salt Excreting Glands Marine birds and reptiles cannot make a concentrated urine. Birds use nasal glands that release salt excretions into the nasal passages. Sea turtles have modified tear ducts that secrete salt into the orbit of the eye.

20. Nitrogenous Wastes Ammonia Urea Uric acid

21. What about rapid ion flux? Euryhaline Short-term fluctuations in osmotic state of environment, e.g. in intertidal zone or in estuaries salinity can range from 10 to 34 ppt with daily tides these fish have both kinds of chloride cells when salinity is low, operate more like FW fishes when salinity is high, operate like marine fishes kidneys function only under low salinity conditions

22. European eel & shore crab

23. Euryhaline Diadromous fishes - spend part of life in salt water, part in freshwater catadromous (migrate seaward) anadromous (migrate up river) hormone-mediated changes associated with metamorphosis – convert from FW adaptations to SW or vice versa, depending on direction of migration

24. How to reduce stress in stressed fish? Minimize the osmotic challenge by placing fish in conditions that are isosmotic add salt to freshwater, e.g. in transporting fish or when exposing them to some other short-term challenge dilute saltwater for same situation with marine species

25. Temperature effects on fish Temperature exhibits the greatest influence on fish Affects metabolism Affects digestion Signals reproductive maturation and behavior

27. Fish are conformers (well, sort of...) Body temperature is that of the environment Each species has particular range of temperatures that they can tolerate and that are optimal Big difference between what you can tolerate and what you thrive in...

28. Hot Fishes Some fish can maintain body temperature greater than ambient - tunas, billfishes, relatives (nearly endothermic) Use retia (similar to rete mirable) in swimming muscles to conserve heat, exchange O 2, etc. Red muscle is medial rather than distal Billfishes have warm brains - heat organ from muscles around eye

29. Freezing Resistance I10-33-Antarcticfish universe-review.ca/

30. Solutions in Antarctic Fish Anti-freeze compounds (AFP) Peptides and glycopeptides Both rich in alanine Molecules adsorb (attach to) surface of ice intefere with ice crystal growth – disrupt matrix Protects cell membranes Ice can rupture cells

31. Antifreeze