EFFECT OF ALUMINUM AND LEAD ON ACTIVITY IN THE FRESH-WATER POND SNAILLYMNAEA-STAGNALIS

Time-lapse video was used to examine the effect of short- (19 h) and l ong-term (1 year) exposure to Al or Pb at neutral pH in static water c onditions on the total distance moved by the freshwater snail Lymnaea stagnalis. Aluminium at 100, 200, 500, or 1000 mu g . L(-1) normally d epressed and Pb al 50 and 200 mu g . L(-1) often increased activity ov er the first 19 h of exposure. Smaller (younger) snails generally show ed greater sensitivity to Al. Exposure to 100 or 500 mu g Al . L(-1) f or up to 30 days caused hyperactivity, but thereafter and 1 year later , activity was similar to controls, suggesting that the snails had bec ome tolerant. Lead (200 mu g . L(-1)) caused continued hyperactivity f or up to 50 days, although movement was significantly reduced after 1 year, suggesting that acclimation had occurred. The effect of Al is in teresting given the supposed limited bioavailability of this metal at neutral pH.