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snail Presentation

  1. 1.
  2. 2. INTRODUCTIONRegression Analysis of Fresh-water Gastropods Distribution Along the San Marcos River <br />Existing State of Knowledge<br />Most invasion gastropods were introduced by humans in aquarium trade<br />Snails are an intermediate host for liver fluke parasite which is fatal to small native fish<br />
  3. 3. Snails of the San Marcos River<br /><ul><li>12 different species of snails (Diaz and Alexander)
  4. 4. For our study’s focus:
  5. 5. Melanoidestuberculata
  6. 6. Tarebiagranifera
  7. 7. HydrobiidaeAmnicolalimosa
  8. 8. Marisa cornuarietis</li></li></ul><li>Melanoidestuberculata<br />(red-rimmedmelania)<br /><ul><li>Were first called “Philippine Horn of Plenty” ion 1937
  9. 9. From southern Asia</li></li></ul><li>Tarebiagranifera<br /><ul><li>Makes up 60% if bottom-dwelling invertebrates of the river
  10. 10. Displaces native snails
  11. 11. Also from southern Asia</li></li></ul><li>HydrodiidaeAmnicola<br /><ul><li>Spire has four whorls
  12. 12. Aperture is dextral
  13. 13. Pathenogenic: females produce eggs without involvement of males</li></li></ul><li>Marisa cornuarietis<br />(giant ram-horn)<br /><ul><li>From South America
  14. 14. About 1 inch in diameter</li></li></ul><li>Snail Anatomy<br /><ul><li>The shell:
  15. 15. Grows by secreting shell material at the edge of the mantle
  16. 16. Opening of the shell is called the aperture</li></ul>dextral<br />Sinistral<br />
  17. 17. Snail Anatomy<br /><ul><li>Movement:
  18. 18. The foot is the muscle that projects from the shell
  19. 19. Slime track of mucous
  20. 20. Not known if movement is dependent on waves of muscular contractions
  21. 21. “hunching” used foot to pull shell forward</li></li></ul><li>Snail Anatomy<br /><ul><li>Feeding and Digestion
  22. 22. Vegetarian: eating chiefly off lawns of living algae, dead plant material and some dead animal matter
  23. 23. Greater activity and food intake at higher temperatures</li></li></ul><li>Predators/Parasites<br /><ul><li>Greatest enemy are the fish: suckers, perch
  24. 24. Some ducks
  25. 25. Invertebrates
  26. 26. Leeches
  27. 27. Ostracods
  28. 28. Intermediate host for parasite: Centrocestusformosanus
  29. 29. Fatal to fountain darter
  30. 30. Originates in Asia</li></ul>Etheostomafonticola<br />
  31. 31. <ul><li>Broader Ecology Context
  32. 32. Invasive species drive out native species</li></li></ul><li><ul><li>Research Questions</li></ul>How do snails feed? breed? respire? move?<br />Do these aspects determine where the snail resides in the river, and to how much effect?<br />What significant do the invasive species pose on the native species of the ecosystem?<br />Hypothesis<br />There will be no difference in snail abundances among<br />different flow regimes, substrate type/size, and/or depth. <br />
  33. 33. Materials and Methods<br />Location<br />San Marcos River at the falls of Spring Lake near Salt Grass<br />When<br />3 separate days in March<br />From 11am-4pm<br />
  34. 34. <ul><li>How
  35. 35. Materials
  36. 36. Two meter sticks
  37. 37. Thermometer
  38. 38. GPS device
  39. 39. Orange
  40. 40. Under Water Digital Camera
  41. 41. Frame</li></li></ul><li><ul><li>How
  42. 42. Technique
  43. 43. Measure average depth
  44. 44. Measure surface flow
  45. 45. Photograph plot for snail count</li></li></ul><li>
  46. 46. <ul><li>Statistical Design
  47. 47. Regression analysis:  analyzing several variables, with a focus on the relationship between the dependent (number of snails and an independent variable (depth, current, substrate size) </li></li></ul><li>RESULTS<br />Fig. 1. Regression analysis, number of snails present as a function of water depth<br />
  48. 48. Fig. 2. Regression analysis, number of snails present as a function of water current<br />
  49. 49. Fig. 3. Regression analysis, number of snails present as a function of substrate size<br />
  50. 50. Fig. 4. Regression analysis of all three variables compared.<br />
  51. 51. Fig. 4. Number of snails present in areas with and without vegetation. Note, only 14 of the 35 sites had vegetation.<br />
  52. 52. DISCUSSION<br />Hypothesis:<br />There will be no difference in snail abundances among different flow regimes, substrate type/size, and/or depth. <br />Compared Results<br />Found in abundance by Kimmel, and Diaz and Alexander.<br />Grantham showed results that support rams-horn have a preference for macrophytes<br />
  53. 53. <ul><li>Limitations of the study
  54. 54. Time
  55. 55. Limited space
  56. 56. Knowledge
  57. 57. Equipment
  58. 58. Broader Ecology Meaning
  59. 59. Insight to why this invasive species is so successful
  60. 60. Influence to endangered fountain darter</li></li></ul><li>

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