Teratogenic effects of the fungicide benomyl on posterior segmental regeneration in the earthworm, Eisenia fetida

Abstract

Earthworms, Eisenia fetida, were treated by surface exposure to the fungicide benomyl at various stages of posterior segmental regeneration. Teratogenic effects of benomyl were observed when worms were treated 7-11 days after amputation (i.e. during the normal period of segmental replication), but not during days 1-5,13-17, or 19-23. Teratogenic effects included a reduction in the number of regenerated segments, an increased frequency of segmental groove anomalies, and a variety of monstrosities. The effects of benomyl treatment on the number of regenerated segments and frequency of anomalies were dose-dependent within a narrow concentration range (approximately 0.2-5.0 mg litre-I); at higher concentrations (e.g. 25 mg litre-') teratogenic effects were less frequent because the onset of segmental delineation was delayed until well after exposure. Non-invasive electrophysiological recordings from treated worms indicated that functional integrity of giant nerve fibre conduction pathways was established in all anomalously regenerated tail segments, except in a two-tailed monstrosity. The evidence supports the hypothesis that these teratogenic effects derive from an antimitotic mode of action of benomyl on segmental regeneration.

Biomarkers in Earthworms

“…A large number of studies have reported general histopathological changes such as bruising and swelling, especially in the clitellum region, tissue necrosis, and extrusion of coelomic fluid (Anton et al 1993;Aspock and An der Lan 1963;Cooper and Roch 1992;E1-Banhawy et al 1986;Gupta and Sundaraman 1988;Hans et al 1990;Karr et al 1990;Sileo and Gilman 1975;Stenersen 1979a;Stenersen et al 1975;Stokke and Stenersen 1993). In addition, Zoran et al (1986) observed teratogenic effects of benomyl in E. fetida under segmental regeneration. The effects have mainly been reported following exposure to organic pollutants, but such changes in earthworms have also been observed following exposure to heavy metal pollution (Gupta and Sundaraman 1990).…”

“…For E. fetida, marked cellular enlargement followed by full depletion of the chloragogenous tissue took place under paraquat exposure (Fischer and Molnar 1992). Doseresponse relationships between the chemical exposure level and the histopatho- Karr et al (1990) Chloragogenous cell PblZn mine spoil D. rubidus Richards and Ireland (1978) Necrosis, loss of Carbofuran (Car) Not stated Sileo and Gilman movement (1975) Vogel and Seifert COONa, CaF2 (1992) Teratogenic effects Benomyl (Benz) E. fetida Zoran et al (1986) '(Car), carbamate; (Benz), benzimidazole; (OC), organochlorine; (OP), organophosphorus compounds.…”

The Effects of Toxic Chemicals on Earthworms

“…In many of the laboratory tests of toxicity, reported in the literature, the species used was not reported. When the species was reported it was usually L. terrestris (Heimbach 1985;Haque and Ebing 1983;Wentsel and Guelta 1987) A. caliginosa (Springett and Syers 1984;Martin 1986;EI Banhawy et al 1986) or E.fetida (Edwards 1983a;Roberts and Dorough 1984;Gestal van et al 1989;Neuhauser et al 1984;Hague and Ebing 1983;Inglesfield 1984;Bouwman and Reinecke 1987;Zoran et al 1986;Drewes et al 1987;Anton et al 1990;Leemput van et al 1989). However, some workers have used a wide range of species including Lampito mauritii Kinberg (Bharathi 1985;Bharathi and Subba Rao 1984) Pheretima posthuma Vaillant (Hans et al 1990) and Octochaetus pattom-6 (Abbasi and Soni 1983), Pheretima hUgendorji Michaelsen (Honda et al 1984).…”

“…Many workers have reported different types of malformations of earthworms in response to exposure to chemicals. For instance, the fungicide benomyl had teratogenic effects on the posterior segment regeneration of the earthworm E. fetida (Zoran et al 1986). These effects included an increased frequency of segmental groove anomalies and a variety of monstrosities, including two tails.…”

Effect of agrochemicals on earthworms

“…Pesticides such as propoxur, methidathion, endosulfan, triazophos, carbofuran, terbufos and methomidophos cause such symptoms. Zoren et al (1986) reported the terratogenic effect of benomyl that is posterior segment regeneration of the earthworm, including an increased frequency of segmental groove anomalies and a variety of monstrosities, including two tails. Anton et al (1990) reported the occurrence of various malformation due to fungicide captan.…”