Attached
TOXIC, CHROMOSOMAL AND MUTAGENIC EFFECTS ON DROSOPHILA MELANOGASTER OF SOME PESTICIDAL FORMULATIONS COMMONLY USED IN SRI LANKA.
1. Nineteen pesticides, namely, Aldrin 25, Antimucin (organo mercurial – compound), Agodrin 60 (monocrotophes), Deenol 25 (DDT), Dipterex 50 (Trichlorphon), Aldrin 20, Fenbar 50 (Sumithion), Folidol (Perathion), Gamalin 20 (BHC), Gramaxone (Paraquat), Heptachlor 23, Intox 8 (Chlordane), Lebaycid 100 (Fenthion), Malathon 50, MCPA 20, Metasystox (Methvl-dementon), Nicotox 20 (Nicotine), Rogor 40 (Dimethoate), and Stam 34 (Propanil) were screened for sex-linked lethal mutations, visible mutations with the specific locus method and crossing over in the male using Drosophila melanogaster as the test organism.
2. The method of treatment used was to feed first –instar larvae on food media to which known concentrations of the pesticidal formulations had been added and then testing the adult males for the above genetic effects.
3. In order to find out the concentrations of the respective pesticides that had to be given to the larvae so as to obtain sufficient number of adult flies for these genetic tests, preliminary concentration-mortality studies had to be conducted. In these studies food media containing various concentrations of each pesticide were tested on first – instar larvae of Oregon (wild type) D. melanogaster and the percentage emergence of adults recorded.
4. The concentration – mortality studies showed that folidol, Dipterex, Intox, Aldrin, Heptachlor, Rogor, Malathion and Lebaycid were extremely toxic to larvae even at such low concentrations as 0.8ppm.
5. The concentration mortality curves for the other pesticides showed that Deenol (DDI), Gamalin (BLC), Andrin, Metasystox (Methyl-demcton), fenbar (sumithion) and Antimucin (organo mercurial compound) had a somewhat linear relationship between concentration and mortality.
6. The pesticides Gramaxone, Stam 3 ¼, MCPA and Nicotox which below a certain threshoid value showed law mortality for a faitly wide range of the concentrations but toxicity increased rapidly above this threshold value.
7. From the above date approximate LC 50 values were calculated and these concentrations, approximated further for practical purposes, were used in the subsequent genetic tests.
9. The specific locus test with the “rucuca” stock did not induce any visible mutations in approximately 5000 to 8000 flies were scored in each experiment. Scoring 5000 to 8000 flies using the “rucuca” stock which has eight markers would mean that, assuming a visible mutation rate of 2x20-5 in Drosophila, only anything above a five- fold increase in mutation frequency could be detected.
A control experiment using EMS (0.075%) gave 2 es (ebony sooty) mutations out of 2582 flies that were counted.
10. Adult males heterozygous for dpbcnbw (dumpy, black, cinnabar, and brown) showed cross – over flies in the progeny of their 1st three day brood when their first instar larvae had been treated with the following pesticides : NCPA, Stam, Cramaxone, Antimucin, Nicotox, Deenol, Endrin, Gamalin, Azodrin and Fenbar.
