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.
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.
In water of various hardness (0.24 mM Ca, 2.5 mM Ca and 3.8 mM Ca) three experimental groups were simultaneously set up: water, water + acetone (0.1%), and water + acetone + lindane 1 mg x l ...super(-1) (1 ppm). Both soft and very soft waters and acetone clearly induced a decrease in the animals longevity. Conversely 1 ppm of lindane increased their expectation of life. The equation of von Bertalanffy always described shell growth relative to acetone control: the value of the parameter k was decreased by 18% in very hard water but only by 7% in soft water and was even increased by 8% in very soft water; the parameter T infinity was reduced by intoxication only in hard and very hard waters. With 1 ppm of lindane a stronger mineralization of the shell was always observed. The fecundity was reduced by 1 ppm of lindane in all cases. Study of fecundity related to size revealed a direct depressor effect of this insecticide on the reproduction of Lymnaea . These results showed that the toxic effect of 1 ppm concentration of lindane was related to the calcium concentration of water.
