Water and Organisms 2

1. Water and Organisms 2 Multicellular strategies

2. Advantage of a body cavity with body fluids separated or isolated from the surrounding water?

3. Body fluid & cytoplasm: • Body fluids & cytoplasm ~ 300 mOsM for most vertebrates • Variable for marine invertebrates, protists, and bacteria, but cytoplasm is close to 300 mOsM • Osmoconformer vs Osmoregulator

4. Multicellular aquatic or marine organisms • Osmoconformers • Internal body fluid  is equal to that of environment but do regulate solutes & ions • Usually requires formation or loss of non-toxic solute • Amino acids, amino acid metabolites, urea, etc. • Osmoregulators • Internal  is regulated independent of environment • Must pump water and/or solutes

7. Remember: cells of an osmoconformer have the same p as the environment, but not the same solute composition!

8. Osmoconformer& Osmoregulator  of Body Fluids (mOsM)  of water (mOsM)

9. How do Osmoconformers adjust the  of the body fluids? • Add or subtract solute molecules from the body fluids • The adjustable solute molecules must be non-toxic and minimally interactive with proteins • e.g., many invertebrates use amino acids and derivatives.

10. Osmoconformer [S]p In Snail Blood p of sea water

11. What is the osmoregulator doing to maintain a constant  ? Stenohaline Euryhaline

12. Salinity tolerance Osmoregulators Osmoconformers Internal  Internal  External  External  Stenohaline Euryhaline

13. Fig 42.2a: Saltwater Fish

14. Saltwater Osmoregulators: body fluids tend to concentrate • Problems: • Gain salt from water • Lose water via osmosis • Strategies • pump out salt • minimize water diffusion

15. Life in Seawater – Vertebrates • Typical solute values (mmol/kg): Modified from Schmidt-Nielsen, K. 1995. Animal Physiology. p. 313

16. Fig 42.2b: Freshwater Fish

17. Freshwater Osmoregulators: body fluids tend to dilute • Problems: • Gain water • Lose salt via diffusion • Strategies • Pump in salt • Minimize water diffusion

18. Life in Freshwater – Vertebrates • Typical solute values (mmol/kg): Modified from Schmidt-Nielsen, K. 1995. Animal Physiology. p. 313

19. Fig 42.6: Salmon - anadromous fish

20. Fig 42.7:Salmon- anadromous fish

21. Other random thoughts: Crocodile tears

22. Other random thoughts: • Sea gull tears • Your goldfish in distilled water • You drinking sea water

25. Fig 42.4: Sharks Urea and methylated amines as osmolytes

26. Fig 42.5: Shark Rectal Gland • The point is to excrete (remove) salt from the body fluids • Accomplished by transporting Na+ and Cl- from body fluids into urine

27. Fig 42.5: Shark Rectal Gland 3 1 2

28. Fig 42.3 Terrestrial

29. Life on Land • 3 possible excretory products (Tab. 42.1)

30. Nitrogenous Wastes: Ammonia • Very toxic • Very soluble in water • Requires lots of water to remove • Fish & aquatic invertebrates

31. Nitrogenous Wastes: Uric Acid • Low toxicity • Not soluble in water • little water loss • Birds and reptiles • hard shelled eggs Terrestrial insects & spiders

32. Nitrogenous Wastes: Urea • Toxic • Soluble in water • Requires lots of water to remove • Mammals & Sharks

33. Minimizing water loss • External covering • Skin or exoskeleton • Long nares • Kidneys that form concentrated urine

34. Final issues to discuss about water balance • Basic kidney functions • Use of Na+ & Cl- gradients to regulate water retention • Shark rectal glands • Insect Malphigian tubules • Vertebrate kidneys • Selling advertising policy

35. Mammalian KidneysInsect Malpighian Tubules • Forms filtrate of blood - isotonic • Reabsorption of wanted solutes • Solutes: amino acids, glucose, Na+, Cl-, Ca++, etc. • Water • Secretion of unwanted metabolites, most of the K+, etc. • Final reabsorption of water is controlled to maintain constant  of body fluids. • The urine is then hypotonic, isotonic, or hypertonic

36. Life on Land – Insects • Based on uric acid (Fig. 42.10) • Pre-urine formed in Malphigian tubules • Hypertonic urine formed in hindgut – Cl– pump & Na+/K+-ATPase

37. Insects: The Point • Minimize water loss • Conserve (retain) Na+ and Cl-

38. Vertebrate and Mammalian Kidneys • Conserve Na+ and Cl_ • Regulate body fluid p by regulating water loss and reabsorption

39. Renal Processes

40. Urinary System:

41. Kidney Layers Fig 89.2

42. The Nephron: Bowman’s Capsule Proximal C T Proximal Straight Tubule Loop of Henle Descending Ascending Distal C T Collecting Duct

43. Fig 19.6: Vascular Component of Nephron Capillaries Vasa Recta

44. Fig 19.7: Renal Processes

45. So the almost final product, urine, enters the collecting duct. Organisms then excrete a dilute urine or reabsorb yet more water if they need to dilute body fluids to maintain proper body fluid osmotic pressure.

46. Medullary Osmotic Gradient

47. Water Reabsorption in DCT & CD

48. Antidiuretic HormoneADH (9 amino acids) • Also called vasopressin • 8 Arginine or 8 Lysine Vasopressin • Released from posterior pituitary • In response to osmo-receptors in hypothalamus • Acts on Collecting Duct to increase water permeability • Causes decreased P & increased blood volume

49. ADH on Collecting Duct

50. Control of Blood Osmotic Pressure • Increased P ---> stimulate hypothalamus osmoreceptors • release of ADH into blood • Acts on CD to increase water permeability • Water diffuses from filtrate / urine into medulla and blood