Pesticide Residues in Soil Invertebrates - Pesticides: Evaluation of Environmental Pollution - page 344

There was impairment of locomotory reflexes at the dosage, which were approximately
two orders of magnitude less than LC 50 . Both carbamates and organophosphorus pesti-
cides inhibit acetylcholine activity (Edwards and Fisher 1991). Carbamates are described
as “extremely toxic to earthworms in comparison to organophosphorus” (Roberts and
Dorough 1984). Symptoms of intoxication to earthworms, which are caused by carbofuran,
include rigidity, immobility, coiling, sores, and segmental swelling, whereas only immo-
bility was observed in the case of organophosphorus pesticides. Aldicarb, endosulfan,
benomyl, and calcium cyanide caused constrictions of the body.
Phorate has been found to be extremely toxic to earthworms and has almost elimi-
nated them from many soils even when applied at normal agricultural doses. Dimethoate
affected the perinuclear position of the Golgi apparatus in the neurons of the nerve cord,
and the Golgi apparatus was fragmented into short elements and granules (El-Banhaway
et al. 1982). In a laboratory study, the fungicide pyrazophos showed the greatest reduc-
tion in population number and biomass dynamics of the earthworm Dendrobaena veneta
(Karaman et al. 1996).
The earthworm Pheretima posthuma is reported to bioaccumulate the nonextractable soil-
bound residues of DDT and HCH (Verma and Pillai 1991) and also found to facilitate the
steady mobilization of soil-bound residues of the insecticide to readily bioavailable labile
forms. The pesticides also affect the growth of fast-growing Eisenia fetida. There is loss of
weight or slowing of growth in some of the species.
Sublethal effects of terbuthylazine and carbofuran on the growth and reproduction of
Eisenia andrei were investigated by Brunninger et al. (1994) over a period of three genera-
tions by measuring the cocoon production of worms. Inhibition of cocoon production was
found in the parental generation.
Hatchlings raised from cocoons to provide the F1 generation grew more rapidly when
treated with terbuthylazine. This increase in vitality was also observed in cocoon pro-
duction. Groups treated with terbuthylazine produced more cocoons than control. The F2
generation was raised from hatchings of the F1 generation, and here, the terbuthylazine
treatments increased earthworms' growth, but not cocoon production. Exposure of carbo-
furan decreased cocoon production in all generations. Growth of the F1 generation was
not influenced by low carbofuran concentration.
The sublethal effect of dieldrin was studied on Eudrilus eugeniae , on the ultrastructure
of spermatozoa. Dieldrin at a relatively low concentration caused structural damage,
especially to the nucleus of the sperm (Reinecke et al. 1995). The burrowing ability and
mortality in earthworm species native to North Canadian forest soils were affected
at relatively low concentrations of organophosphorus pesticides such as fenitrothion.
Dendrobaena octaedra , the forest litter-dwelling species, was approximately eight times
more sensitive to the chemical than E. fetida . However, when D. octaedra was exposed to
the pesticide in litter, the earthworm was considerably less susceptible to fenitrothion
(Addison and Holmes 1995). Diflubenzuron, an insect growth regulator, showed little
effect on mortality and gross anatomical changes of earthworms. This is because earth-
worms have no chitin in their body (Maurya and Chattoraj 1994).
Fumigants such as dichloropropane and dichloropropene applied to the soil for the
control of pathogens and nematodes permeate the soil as vapors and kill most of the
earthworms, even those that live in deep burrows. Chloropicrin is also very toxic to all
earthworms.
Xiao et al. (2006) suggested that growth can be regarded as a sensitive parameter to eval-
uate the toxicity of acetochlor on earthworms. Helling et al. (2000) tested in laboratory the
effect of copper oxychloride, while Yasmin and D'Souza (2007) investigated the impact of