Valve movement behaviour and byssal formation of the mussel, Mytilus edulis in relation to environmental toxins

Abstract

The present investigation was undertaken to determine behavioural responses of mussel, Mytilus edulis, to sub-lethal concentrations of lindane and atrazine. Behaviour effects that have been studied in mussels were byssus formation, valve movement and valve gape. Lindane was more toxic, causing a 46% reduction of byssal formation, compared to control, after 7 days exposure to 0.9 mg/l. However, atrazine caused 50% reduction of byssal formation after 14 days exposure to 3.585 mg/l atrazine. The sensitivity of the tests increased with increasing the exposure time. Measurements of valve movement and gape showed that increasing exposure and accumulation of lindane increased the proportion of time spent resting (a closed to open ratio of 1.31 at 56 days, compared to a value of 0.05 in the controls). On the other hand, with atrazine the valves did not shut completely (valve closed to open time ratio of 0.3 at 56 days compared with a control value of 0.08) but were observed to have a smaller gape (average gape at 56 days 8.7 mm) than control mussels (average gape at 56 days 25.5 mm). The data of valve movement indicate that the rest period has increased by increasing the concentration and the time of exposure to lindane. Byssus formation in M. edulis was progressively reduced with time of exposure to the 1/2 LC50 of the two pesticides. The byssogenesis test was proved to be a sensitive test in mussels and is suggested as a convenient and rapid technique for bioassay of potential pollutants.


KEY WORDS: Mussels, valve movement, byssal formation, lindane and atrazine.


Egyptian Journal of Biology Vol.3(2) 2001: 63-71