title: The sublethal effects of sulphide on Arctica islandica and Mytilus edulis
Creators: name: Butterworth, Kevin Geoffrey
Publisher: name: University of Glasgow
Year: 2002
Subjects: subject: Physiology.

description: The aims of this thesis were to examine the effects of sulphide on two species of bivalve, Arctica islandica and Mytilus edulis. All the experiments were designed to maintain aerobic conditions throughout, in an attempt to separate the effects of sulphide from those of hypoxia. Initially the LT50 values for both A. islandica and M. edulis were established (Chapter 2). It was apparent from the results of the LT50 experiments that the A. islandica from a sulphide-rich habitat had longer survival times than those from a low-sulphide habitat. There was also a significant difference in the average shell height of the A. islandica from both areas, with the mean height of the A. islandica from the low- sulphide area being almost double the size of those from the sulphide-rich area. A. islandica were very resistant to sulphide, with an LT50 of 6 - 8 weeks, depending on the concentration of the sulphide, whereas M. edulis had an LT50 of only 1 - 3 weeks. However, both A. islandica and M. edulis were found to undergo an increase in body condition upon exposure to sublethal concentrations of sulphide for extended periods (Chapter 2). Further analysis of the LT50 survivors showed that the condition index (shell meat volume to inner shell volume ratio) increased consistently with sulphide exposure in both A. islandica and M. edulis. These results may indicate that the bivalves are able to utilise the reducing potential of sulphide as an energy source. Experiments were carried out to examine the effect of sulphide on the ventilation rate of M. edulis (Chapter 3). During sulphide exposure, M. edulis remained open and continued to ventilate at all the sulphide concentrations tested. This appeared to indicate that this bivalve was unable to detect sulphide at concentrations between 0 muM and 1200 muM. Furthermore, the results suggested that M. edulis was maintaining aerobic respiration in the presence of sulphide. Experiments were designed to examine the physiological response of isolated hearts from M. edulis to sulphide exposure (Chapter 4). The results indicated that it is the H2S ion species of sulphide that elicits a response in the isolated hearts. It was possible to acclimatise M. edulis to sulphide, and the acclimatisation appears to occur at an intracellular level, suggesting that a response to sulphide exposure is induced. The concentrations of succinate in selected tissues of intact M. edulis and A. islandica showed no significant changes upon exposure to increasing concentrations of sulphide. Thus there was no evidence of anaerobiosis. It appears, therefore, that the intact M. edulis and A. islandica did not switch to anaerobiosis during exposure to sublethal concentrations of sulphide under normoxic conditions. Furthermore, succinate was demonstrated not to be a reliable indicator of anaerobiosis in the presence of sulphide, due to the effect of the redox potential of sulphide on succinate dehydrogenase and fumarate reductase (Chapter 6). (Abstract shortened by ProQuest.).