Acute exposure of the freshwater gastropod Planorbarius corneus to an environmental concentration of chlorpyrifos. Recovery studies of enzyme activities in gonads and effects on reproduction

RIVADENEIRA, P. R; AGRELO, M; KRISTOFF, G.

Chlorpyrifos: Toxicological Properties, uses and effects on human health and the environment?

Nova Publishers

Año: 2015; p. 27 - 38

Chlorpyrifos is an organophosphate insecticide widely used in a variety of food crops in Argentina and other countries. In a previous work, we have reported that subchronic exposure (14 days) to an environmental concentration of chlorpyrifos (5 µg L-1 ) caused severe effects on reproduction of the freshwater hermaphrodite gastropod Planorbarius corneus. The aim of the present work was to study the effects of chlorpyrifos on the reproduction of this adult snail after an acute (2 days) exposure. Also B-esterase activities (cholinesterases and carboxylesterases) were measured in the gonads, to study the possible link of the biochemical responses to the reproduction effects. Snails were exposed during 2 days to 5 µg L-1 of chlorpyrifos. Water control and solvent control (acetone) group were included in the bioassay. After 2 days of exposure, some snails per group were used to measured enzyme activities and other snails were transferred to water. Then, the bioassay was continued for 14 days. Snails were fed once a week. During the 14 days in water, the number of egg masses was registered and, for each egg mass, the number of egg masses without eggs, the number of eggs per mass, the time for hatching, the hatchings and the survival of the offspring were counted. After 2 days of exposure and after 2 and 14 days in water, snails were placed on ice, the shells were removed and gonad homogenates were realized. Supernatant fraction (6 for each time and for each group) was used to measure cholinesterase and carboxylesterase activities and protein content. After an acute exposure, 5 µg L-1 of chlorpyrifos caused a decrease on cholinesterase activity using acetylthiocholine as substrate (45 %) and carboxylesterase activities (26 % using p-nitrophenyl acetate as substrate and 40 % using p-nitrophenyl butyrate) in gonads. After 14 days in water, no recovery of cholinesterase activity was observed. However, carboxylesterases measured with both substrates returned to control values. Regarding the reproduction effects, only an increase in the number of egg masses without eggs and an increase in the time for hatching were observed. Recovery of carboxylesterases in gonads could be related to the lower effects observed on reproduction in comparison with the subchronic exposure. After 14 days of exposure, 5 µg L-1 of chlorpyrifos had produced a strongly decrease in B-esterase activities and severe effects on reproduction, such as the decreases in the % of hatching and survival of the offspring, the increases in egg masses without eggs and in the time of hatching. Exposures to environmental concentrations of chlorpyrifos caused different toxic effects on the reproduction of Planorbarius corneus depending on the time of exposure.