2. INTRODUCTIONRegression Analysis of Fresh-water Gastropods Distribution Along the San Marcos River Existing State of Knowledge Most invasion gastropods were introduced by humans in aquarium trade Snails are an intermediate host for liver fluke parasite which is fatal to small native fish

4. For our study’s focus:

5. Melanoidestuberculata

6. Tarebiagranifera

7. HydrobiidaeAmnicolalimosa

10. Displaces native snails

12. Aperture is dextral

15. Grows by secreting shell material at the edge of the mantle

16. Opening of the shell is called the aperturedextral Sinistral

18. The foot is the muscle that projects from the shell

19. Slime track of mucous

20. Not known if movement is dependent on waves of muscular contractions

22. Vegetarian: eating chiefly off lawns of living algae, dead plant material and some dead animal matter

24. Some ducks

25. Invertebrates

26. Leeches

27. Ostracods

28. Intermediate host for parasite: Centrocestusformosanus

29. Fatal to fountain darter

30. Originates in AsiaEtheostomafonticola

33. Materials and Methods Location San Marcos River at the falls of Spring Lake near Salt Grass When 3 separate days in March From 11am-4pm

35. Materials

36. Two meter sticks

37. Thermometer

38. GPS device

39. Orange

40. Under Water Digital Camera

42. Technique

43. Measure average depth

44. Measure surface flow

48. Fig. 2. Regression analysis, number of snails present as a function of water current

49. Fig. 3. Regression analysis, number of snails present as a function of substrate size

50. Fig. 4. Regression analysis of all three variables compared.

51. Fig. 4. Number of snails present in areas with and without vegetation. Note, only 14 of the 35 sites had vegetation.

52. DISCUSSION Hypothesis: There will be no difference in snail abundances among different flow regimes, substrate type/size, and/or depth. Compared Results Found in abundance by Kimmel, and Diaz and Alexander. Grantham showed results that support rams-horn have a preference for macrophytes

54. Time

55. Limited space

56. Knowledge

57. Equipment

58. Broader Ecology Meaning

59. Insight to why this invasive species is so successful