Acute physiological responses of the freshwater snail Elimia flava (Mollusca: Pleuroceridae) to environmental pH and calcium.
The individual and interactive effects of environmental pH (7 [control], 6, 5, and 4) and calcium (0, 5, and 50 mg/L) were studied on hemolymph ions (pH, Ca(2+), total CO(2), Na(+), K(+)) and osmolality in the freshwater snail, Elimia flava, over a 72-h exposure. All hemolymph factors strongly differed with environmental pH. Snails exposed to pH 4 were inactive and experienced more dramatic ionic disturbances than snails at pH 5, 6, and 7, including reduced hemolymph pH, depressed Na(+) concentrations, and increased Ca(2+) and total CO(2) concentrations. There was an initial but transient increase in hemolymph K(+) over the 72 h exposure period. Environmental calcium ameliorated effects of acidification on hemolymph pH and Na(+), reducing the degree of depression in both variables irrespective of environmental pH or exposure time. In a separate experiment, effects of acidification on snail respiration were examined in which VO(2) was measured over 24 h in snails exposed to pH 7 and 4. Exposure to pH 4 caused a 64% reduction in oxygen uptake at 2 h and a maximum reduction (81%) at 11 h. Our results suggest that snails exposed to pH 4 cease interacting with the surrounding medium and use internal stores of CaCO(3) to buffer hemolymph acidification, whereas snails at pH 5 and higher appear to use environmental calcium as a buffer source. These results suggest an important role of environmental calcium in ameliorating the impacts of short-term, sublethal acidification.
Outreach Education, College of Sciences and Mathematics, 131 Sciences Center Classroom, Auburn University, Auburn, Alabama 36849-5434, USA. ewaldml@auburn.edu
Mary Lou
ML
Ewald
Jack W
JW
Feminella
Kristin K
KK
Lenertz
Raymond P
RP
Henry
D000222:Adaptation, Physiological; D000818:Animals; D002021:Buffers; D002119:Calcium Carbonate / Q000097:blood*; D002245:Carbon Dioxide / Q000097:blood; D017753:Ecosystem; D005618:Fresh Water / Q000737:chemistry; D006458:Hemolymph / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008974:Mollusca / Q000378:metabolism*; D009994:Osmolar Concentration; D010101:Oxygen Consumption; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood; D013312:Stress, Physiological; D013997:Time Factors
D002021:Buffers; D002245:Carbon Dioxide; D012964:Sodium; D002119:Calcium Carbonate; D011188:Potassium