Population differences in susceptibility to stress in Littorina saxatilis from metal contaminated and uncontaminated sites in the Isle of Man

摘要

The population of the intertidal gastropod Littodna saxatilk from Laxey estuary in the Isle of Man is exposed to mine-related contamination of Zn (and is tolerant to Zn and Pb) compared to those of Castletown, Derbyhaven, Peel and Ramsey. Tolerances to salinity and desiccation stress were assayed to test how metal tolerance could affect tolerance to general stress. The winkles were experimentally exposed to salinities of 0, 17 and 60 practical salinity units (psu) with 34 psu as control. Desiccation stress was determined by aerial exposure of the winkles at 24 deg C. No control mortalities were recorded and mortalities in 17 psu were less than 50 percent for all populations over a 24-day exposure period. LT_(50) values (mean+ - SD, n=5) at 0 psu ranged from 6.6 + 0.6 to 7.5 +-1.3 d for winkles from Ramsey and Laxey respectively. The values for 60 psu ranged from 7.0 +0.7 to 8.4 +0.9 d. No significant differences in LT_(50) values were obtained for the salinity exposures(ANOVA, P>0.05) but there was a significant difference in tolerance to desiccation (P<0.01). The winkles from Laxey showed very high susceptibility to desiccation stress probably indicating a physiological trade-off to metal tolerance.