1. INVERTEBRATES AND FLUID DYNAMICS: HOLDING ON

2. BOUNDARY LAYER Mainstream Velocity (U) Boundary layer thickness (99%) Boundary layer thickness (90%) Distance from substrate Velocity

3. BOUNDARY LAYER Using the boundary layer – water pennies (Psephenidae)

4. BOUNDARY LAYER Mainstream Velocity (U) Distance from substrate Velocity

5. BOUNDARY LAYER Using the boundary layer – water pennies (Psephenidae)

6. Other stream insects Plecoptera Trichoptera Ephemeroptera

7. Stream animals– Strategies for holding on Baetis Rhithrogena Ancylus

8. Psephenus Neothremma Bibliocephala Stream animals– Strategies for holding on

9. Extreme Gradients – Swash Zone

10. Donax

11. Swash Surfing

12. Donax Density Shape Weight distribution

13. Density 2.0 1.0 0 Density (10 3 kg/m 3 ) Donax Chione Mercenaria Spisula Macrocallista Divaricella Tellina Tagellus

14. Weight Distribution Pivot point

15. AnteriorPosterior Ventral Dorsal

18. Behaviour in a Swash Zone

21. WAVE STRESS a. Limitation of size Water flow 100% 90% Boundary layer

22. WAVE STRESS a. Limitation of size Water flow

23. WAVE STRESS b. Holding on – flow tolerance Flow rate (m/s) 3 0 Time to dislodge

24. WAVE STRESS c. Holding on - orientation Keyhole limpet

25. WAVE STRESS c. Holding on - orientation Water flow

26. WAVE STRESS c. Holding on - orientation <.5 m/s -90090 >.5 m/s Freq Orientation (º to flow)

27. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 1. Testing holding power

28. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 1. Testing holding power Kg required to dislodge 100 0 Foot area (cm 2 ) 15

29. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 1. Suction? Atmospheric pressure ≈ 1 kg/cm 2 Patella ≈ 3 - 7 kg/cm 2 -can’t generate a force > atmospheric pressure - No negative pressure under foot

30. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Patella Mucous layer

31. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 2. Adhesion area surface tension Thickness of fluid Theoretical adhesion = 600 kg/cm 2

32. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 2. Adhesion Tenacity (kg/cm 2 to detach) Weight of mucous

33. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Foot rigidity

34. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Foot rigidity l d

35. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Foot rigidity Tenacity Flexibility High Low In field -

36. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Drag FLOW Resistance to water movement depends on: 1) Size 2) Shape 3) Texture

37. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Drag SideFrontRear Drag – not well correlated with density

38. Types of Limpets Non-MigratoryMigratory -don’t move far -often fixed and territorial -low r -low growth -move up shore -high r -high growth (need high food intake) -react to predators by clamping-flee from predators LESS FLEXIBLEMORE FLEXIBLE

39. A COMPROMISE OF SEVERAL FACTORS Sea Urchins - Echinoidea lunules

40. WHAT IS THE FUNCTION OF LUNULES? 1) Aid in burrowing 2) Removal of feces 3) Maintain a “communication” with the surface if buried 4) Maintain inclined posture 5) Feeding

41. Log lunule length Log test diameter p <.05 If lunules have a hydrodynamic function -they should grow with the animal isometric observed

42. Time to burrow Burrowing speed PluggedNot plugged 230 sec 231 sec

43. Flow through a sand dollar

44. Lift Weight

45. Lift Weight Burrowing to add weight

46. Sand Dollar reorientation - Dendraster

47. Adding weight – incorporate magnetite

48. Reducing lift and drag Skin drag – important? Pressure drag – depends on shape

49. Reducing lift and drag Skin drag – important? Pressure drag – depends on shape Very flat

50. Reducing lift and drag Skin drag – important? Pressure drag – depends on shape Rounded Area of lower pressure

51. How do you reduce lift Reduce pressure differential between upper and lower surfaces

52. Can sand dollars tell the direction of orientation? Anterior Posterior

53. Can sand dollars tell the direction of orientation? -inverted sand dollars – can flip over more easily with posterior edge facing upstream (i.e critical velocity to re-orient is lower) Hardy & Merz. 2013. Invert. Bio 132:52 Initial orientation Final orientation (1 hr)