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Sara A. Lombardi & Kennedy T. Paynter Marine Estuarine Environmental Science University of Maryland College Park, M

Differences in the gaping response and hemolymph pH of the eastern oyster Crassostrea virginica and the Asian oyster Crassostrea ariakensis when exposed to hypoxic environments. Sara A. Lombardi & Kennedy T. Paynter Marine Estuarine Environmental Science University of Maryland

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Sara A. Lombardi & Kennedy T. Paynter Marine Estuarine Environmental Science University of Maryland College Park, M

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  1. Differences in the gaping response and hemolymph pH of the eastern oyster Crassostrea virginica and the Asian oyster Crassostrea ariakensis when exposed to hypoxic environments Sara A. Lombardi & Kennedy T. Paynter Marine Estuarine Environmental Science University of Maryland College Park, MD USA

  2. Oysters and the Chesapeake Bay • Population decline of Crassostrea virginica • 1% of historic population(Newell 1988) • Ecosystem service decline • Before 1870: 6 day Bay filtration • Now: approximately 325 days (Newell 1988) • Introduction of C. ariakensis as a solution? • Increased comparisons between the species • Growth • Perkinsismarinusinfection (Dermo)

  3. C. virginica and C. ariakensis during low oxygen “C. ariakensis began gaping during the sparging process ….. The native oyster remained closed until 1-2 days before its death” Harlan 2007

  4. Why gape? • Risk: Greater exposure to predators • Probably a physiological underpinning • Is gaping a response to release CO2? • Acidic metabolic byproducts accumulating in the hemolymph CO2 + H2O H2CO3  HCO3- + H+

  5. Objectives Compare the physiological responses of Crassostrea ariakensis and Crassostrea virginica to low oxygen • Assess gaping response after hypoxic exposure • Frequency of gape • Extent of gape • Analyze correlations between gaping and external water pH • Inhibit gaping and assess hemolymph pH • Effect of time • Effect of species

  6. Gaping Study Methods • Oysters from Horn Point Lab, Cambridge, MD • Starved for 1 week in 15ppt 25° C water • Respiration chambers filled and sparged until oxygen concentration below 0.5mgL-1 • Individual oysters were placed into a chamber which was then sealed • At periodic intervals, oyster gaping response was assessed • 8-72 hours after hypoxic immersion the pH of the water surround each oyster was analyzed. • Repeated Measure Analysis of Variance

  7. Gaping Response 12 hrs 10 days • C. ariakensis gapes more often than C. virginica (p<0.0006)

  8. Gape Distance C. ariakensis gapes to a greater degree than C. virginica during early (0-72 hours) hypoxic exposure(p=0.0057)

  9. Gaping and Water pH • Gaping is correlated with acidic external environments (p=0.034)

  10. Hemolymph pH Methods • Clamped using 2” binder clips and placed on lab bench at ~25° C air temperature • Sacrificed at hr 0 (control), 2, 4, 6, 8, 10, 12, & 24 • Dorsal and ventral side drilled • Hemolymph sampled with 5ml glass syringe • pH analyzed with bench top meter and micro pH probe • Performed Perkinsismarinus analysis • Excluded those with P. marinus score greater than 1 from analysis • Two-way ANOVA

  11. Hemolymph pH after clamping Species: p<0.0001 Time: p<0.0001 Interaction: p=0.2934

  12. Change in hemolymph pH after clamping * Species: p= 0.0214 Time: p<0.0001 Interaction: p=0.2934 *

  13. Conclusions • C. ariakensis gapes more often than C. virginica (p<0.0006) • C. ariakensis gapes to a greater extent than C. virginica (p=0.0057) • Gaping is correlated with acidic external environments (p=0.034) When gaping is prevented… • C. ariakensis hemolymph pH is more acidic than C. virginica (p<0.0001)

  14. Conclusions and Implications • C. ariakensis may respond differently to low oxygen and different acid-base homeostatic abilities • Gaping may be a mechanism to prevent or limit metabolic acidosis in C. ariakensis

  15. Next steps • Assess pH over time simultaneously with calcium and carbon dioxide concentration • Assess hemolymph pH of gaping and ungaped oysters when exposed to low oxygen • Effect of gaping on hemolymph pH • Assess the effect of acidosis on adductor muscle function

  16. References Acknowledgements • Funding • Oyster Recovery Partnership • National Oceanographic and Atmospheric Administration – Chesapeake Bay Office • Army Corp of Engineers – Baltimore district • University of Maryland’s Horn Point Lab Oyster Hatchery • Dr. Donald Merrit • Stephanie Tobash Alexander • University of Maryland • Paynter lab staff and students • Dwyer J. J & Burnett L.E 1996. Acid-base status of the oyster Crassostrea virginica in response to air exposure and to infections by Perkinsus marinus. Biol. Bull. 190 :13-137 • Newell R. I. E 1998. Ecological changes in Chesapeake Bay: Are they the result of overharvesting the American oyster, Crassostrea virginica? Understanding the estuary: Advances in Chesapeake bay research. Proceedings of a conference 29-31. Chesapeake Research consortium publication 129. • Harlan N.P. 2007 A comparison of the physiology and biochemistry of the eastern oyster, Crassostrea virginica, C. ariakensis. Masters of Science. • Stickle W.B., Kapper M.A, Liu L., Gnaiger E., & Wang S.Y. 1989. Metabolic adaptations of several species of crustaceans and Molluscs to Hypoxia: Tolerance and Microcalorimetric studies. Biological Bulletin 177:303-312

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