PARENT SESSION
4F Alternatives for risk assessment in terrestrial ecosystems
9:00 AM to 7:00 PM, Monday, 07 May 2001

(M/MF154) Effects of sub-lethal dimethoate dosing on locomotor behaviour of Porcellio dilatatus (Crustacea: Isopoda)).

Engenheiro, Elisabete^{1, 2}, Hankard, Peter², Weeks, Jason², Sousa, Jose¹, Soares, Amadeu^{1, 3}, ^{1 2 3}

ABSTRACT- Locomotor behaviour is crucial for burrowing, avoiding predators, food seeking, migration and reproductive behaviour (Sutton, 1972) and can be quantifiable with the aid of a computer-aided video tracking system. In this study, the locomotor behaviour of Porcellio dilatatus taken from laboratory cultures was quantified for 4 hours following exposure to dimethoate by topical application with a 2l micropipette. Dimethoate was applied dissolved in acetone: olive oil at a 19:1 ratio (carrier). The doses applied were 5g/g, 10g/g, 15g/g, 20g/g and 25g/g of animal. The carrier was used as a control and the doses applied were under the LD₅₀ (calculated to be 24g/g of animal after 48h of exposure), except for the highest dose. For each treatment 18 animals were tracked and weights registered. The animals were frozen after tracking for further measurements of biochemical and physiological parameters. The locomotor parameters measured were total distance moved, maximum and average velocity, total rest time, total active time, turning rate and turning bias. Exposure to the two highest concentrations provoked hyperactivity in relation to the controls in terms of mean velocity and an increase in turning rate. At the three lowest concentrations, animals showed a decrease in rest time and consequently an increase in active time in relation to the controls. The obtained results will be analysed in terms of increase or decreased in activity and will be related to ongoing studies on increased and decreased AChE activity.

Key words: Locomotor behaviour, dimethoate, tracking system, Porcellio dilatatus