BUILDING BIGGER AND BETTER ANIMALS SUPPORT AND LOCOMOTION

1. BUILDING BIGGER AND BETTER ANIMALS SUPPORT AND LOCOMOTION

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

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 (SO2)] Calcareous [Calcium (CaCO3)] Spongin [Protein]

8. Arrangement of spicules can be haphazard or very precise

10. Mesoglea

11. Collagen

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

13. Collagen Fibres in Metridium circumferential radial

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

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

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

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 300% 300 150 0 Extension (%) 30% Normal If cross-linked

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

25. Jellyfish Shapes Prolate Oblate

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

27. Jellyfish Shapes Fineness Prolate Oblate

28. Swimming of Prolate and Oblate Jellyfish Prolate Oblate 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 fluid muscle

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

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

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

34. In the molluscs 3) Monotaxic 4) Ditaxic

35. Changes in locomotion Confronts obstacle Gibbula

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

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 2 points d’appui Caterpillars Leeches