Chronic intoxication by an herbicide, 2,4,5-trichlorophenoxyacetic acid, in the pond snail, Lymnaea stagnalis L.

Experiments of chronic intoxication with three concentrations (10, 20, and 40 ppm) of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were conducted in the freshwater mollusc Lymnaea stagnalis. Snail survival was concentration dependent. In all cases the growth can be described by the von Bertalanffy pattern (ht = h (1 - e-k(t-to)) and the variations of the k values showed that growth was significantly altered in all the groups treated. The overall fecundity (F) was always reduced; the decrease was due both to a lower number of eggs per egg mass (-7.8 to -12%) and to an earlier death of the intoxicated snails. Fecundity studied in terms of size, according to the law F = ahz, points out the loss of equilibrium between growth and fecundity: in all groups treated the values of the exponent z were increased. The importance of these perturbations can be quantified by the calculation of a "Snail Yield" which is reduced by 72.6% in the 40 ppm group. Egg fertility was also reduced. It can be concluded that 2,4,5-T disturbs the physiological equilibrium of Lymnaea stagnalis leading even to earlier death of the snails.

Chronic toxicity of acetone in the fresh water snail Lymnea stagnalis.

With water of total hardness of 230 mg/l of CaCO3 all the tried concentrations (0.1, 0.2, 0.4 and 0.6%) of acetone induced a decrease in the growth of the young pond snails. For older snails, a 0.4% concentration was the threshold at which an inhibitory effect of the shell growth was observed. From the 0.1% concentration a decrease in the shell mineralization was recorded. In the range of 0.1--0.6% concentrations, the decrease of the fecundity varied from 3% to 31%. At lowest concentrations, only the number of egg-masses/snail was reduced. At the 0.6% level a lower number of eggs/egg-mass was added. The 0.6% concentration of acetone disturbed only the fertility of the eggs; lowest concentrations significantly increased the frequency of polyembryony.

[Action of detergent products in the aquatic larvae of Chaoborus and Cloen: importance of their physiological activity (author's transl)]. / Action de produits détersifs chez les larves aquatiques de Chaoborus et de Cloeon: importance de leur état physiologique.

For the Chaoborus larvae (Diptera), the toxic effect of detergents depend on their physiological activity: the diapausing animals are less sensitive. On other respects, the speed of this effect is linked to the chemical composition of the detergents. For the Cloeon larvae (Ephemeroptera) these products seem to interfere with the molting process: some of them induce a decrease in the molting frequency, others are without effect; on the other hand a commercial washing powder induces a real increase of this frequency.

[Acute toxicity of 5 pollutants on 4 fresh-water invertebrate species]. / Toxicité aiguë de 5 agents polluants sur 4 espèces d'invertébrés habitant les eaux douces

The animals stay in solutions for 4 days at different concentrations of each agent: regression lines (log concentration-probit) allow us to calculate the lethal concentration values for 50% of the animals tested (LC 50). Animals are affected by concentrations ranging from 0,003 to 9,0 X 10(-6) of insecticides, 2 to 16 X 10(-6) of herbicide, 9 to 50 X 10(-6) of detergents. As a general rule, the four studied species can be classified by decreasing sensibility in the following order: Gammarus, Cloeon, Chaoborus and Lymnea.