Earthworms (Dendrobaena veneta) reproduction and population response to 2,4-D toxin

Dendrobaena veneta is one of the most common epigeic earthworm in many orchard soils that is exposed to various toxins. The purpose of this paper was to investigate the effects of an agricultural toxin (2, 4-D herbicide) on reproduction and biomass of D. veneta in fruit orchard soils of Esfahan province.The Dendrobaena veneta earthworms were obtained from the soils of apple orchard. All tests were performed using adult earthworms with individual weight from 300 to 600 mg. 10 earthworms were transferred to each plastic box with 1000 g of soil prepared by adding different concentrations of 2,4-D herbicide (1; 10; 50; 100; 500; 1000 mg/kg). After 15, 30 and 60 days of incubation, earthworms were sampled, identified and weighed.The effect of 2, 4-D was observed at all test concentrations when compared to untreated soil. 90% mortality was observed a day after exposure of earthworms in soil treated with 500 and 1000 mg/kg. After 15 days, mortality was around 40% of earthworm in all the other concentrations. No cocoons or juveniles were found in any experiment using soil containing 2, 4-D.The results showed that the decrease in weight was time and concentration dependent over the 60 days of exposure, which indicated statistical significance for both parameters (p˂0.05). In soils treated with 2,4-D, the observed effects (death of earthworms after a few hours of exposure and loss of weight) are consistent with acute toxicity symptoms. 2,4-D showed severe effects on the development and reproduction of Dendrobaena veneta in laboratory tests.

Keywords:

Dendrobaena veneta , 2 , 4-D , earthworm , reproduction