1. BUILDING BIGGER AND BETTER ANIMALS SUPPORT AND LOCOMOTION

2. Pandorina Pleodorina Eudorina Gonium Chlamydomonas Volvox Beginnings of the Metazoa?

3. Metazoan Evolution Two consequences 1) Need for support 2) Need for coordinate locomotory apparatus Design of the support system Method of movement

4. Going to look at 1) Sponges 2) Hydrostatic skeletons – anemones and jellyfish 3) Acoelomates 4) Molluscs 5) Exoskeletons 6) Notochords

5. Anatomy of an Asconoid Sponge

6. - spicules embedded in the mesohyl Same principle as putting straw in mud bricks

7. Sponge structure - Support Siliceous [Silica (SO 2 )]Calcareous [Calcium (CaCO 3 )] Spongin [Protein]

8. Arrangement of spicules can be haphazard or very precise

9. The Cnidarians

10. Mesoglea

11. Collagen

12. Collagen Fibres in Metridium unstressed angle – 40 – 45º 1) Crossed helices (outer layer)

13. Collagen Fibres in Metridium circumferential radial

14. Composition of anemone body 92% 8% 85% 9%6%

15. Behaviour of collagen Stress test - mesoglea 300% original length Stretch for 12-15 hrs Release load Stress test - collagen 102% of original length Stretch for 12-15 hrs Release load How can mesoglea (85%) collagen stretch to 300% if collagen itself stretches only 2%?

16. Behaviour of collagen 1) Matrix in which it sits is important 2) Collagen fibres are not joined How can mesoglea (85%) collagen stretch to 300% if collagen itself stretches only 2%?

17. Slide past one another

18. What is in the mesogleal matrix? High molecular weight polymer - protein / polysaccharide complex Dilute gel

19. What is in the mesogleal matrix? Collagen fibres not directly cross-linked Extension (%) NormalIf cross-linked 300 150 0 300% 30%

20. Why aren’t they cross-linked? +/- weak cross-links +/- seawater ions

21. Preserved Anemone - matrix is cross-linked by formaldehyde

22. How do they move? – Cnidarian nerve nets

23. Simplified Scyphozoan Anatomy Velum

24. Jellyfish Shapes Collin & Costello 2002. J.Exp.Biol.205: 427 Prolate Oblate

25. Jellyfish Shapes ProlateOblate

26. Jellyfish Shapes Collin & Costello 2002. J.Exp.Biol.205: 427 h d

27. Jellyfish Shapes Fineness ProlateOblate

28. Swimming of Prolate and Oblate Jellyfish ProlateOblate Opening of bell Closing of bell Opening of bell Closing of bell

29. Hydrostatic skeleton For a fluid the change in pressure is equal in all directions Δp contracting area

30. Hydrostatic skeleton How do you apply pressure? Either 1) Add fluid to system 2) Move fluid around muscle fluid

31. A slight diversion – Acoelomates and Molluscs Nemerteans Platyhelminthes Molluscs

32. Direction of wave Direction of motion Movement in Aceolomates/Molluscs 1) Direct

33. Direction of wave Direction of motion Movement in Aceolomates/Molluscs 2) Retrograde points d’appui

34. 4) Ditaxic3) Monotaxic In the molluscs

35. Changes in locomotion Gibbula Confronts obstacle

36. Snail has peculiar problem Remember the standard coelomate body plan. Step 2 - Put a fold of tissue dorsally Step 1 - Expand the lower body wall Step 3 - Put a shell over top How do you build a mollusc?

37. Snail has peculiar problem How do you build a mollusc? Visceral mass + shell Foot Problem of torque (or twisting)

38. Snail has peculiar problem How do you build a mollusc? Problem of torque (or twisting) Columnar muscles

39. Extremes of this kind of locomotion Leeches Caterpillars 2 points d’appui