Arch. Environ. Contam. Toxicol. 23, 375-382 (1992)
A~hives
of
E nvironmental
c o n t a ma nidn a t i o n | oxicology
© 1992 Springer-Verlag New York Inc.
Long-term Effects of Heavy Metals in Food on Developmental Stages of Aiolopus thalassinus (Saltatoria: Acrididae) Gerhard H. Schmidt*, Nabil M. M. Ibrahim**, and Mounir D. Abdallah** *Lehrgebiet Zoologie-Entomologie, FB Biologie, Universit/it Hannover, Herrenh~iuserStrasse 2, W-3000 Hannover 21, Federal Republic of Germany and **Department of Economic Entomology and Pesticides, Faculty of Agriculture, Cairo University, Giza, Egypt Abstract. Newly hatched F~ nymphs of Aiolopus thalassinus (Fabr.) were fed on food treated with various concentrations of HgCI2, CdC12, and PbC12 until the end of adult life. Toxicological observations were followed in the FI generation and in the F 2 generation derived from the heavy metal-loaded FI parents. The highest concentration of the heavy metals caused 100% mortality of the F1 adults within four weeks. The nymphal duration of the Fl and F 2 generations was significantly prolonged after Hg and Cd exposure, but the Fj of the group treated with lead was not affected. The fresh body weight of adults was significantly reduced in the F~ generation of most treatments and in the resulting untreated F 2. The lifespan of the F~ adults was shortened. In the F 2 generation, although the lifespan was somewhat longer, generally it was still shorter than that of the control adults. The mean egg number laid by F~ adults fed on food contaminated with Hg or Cd was decreased. This decrease was more pronounced in the case of Cd than Hg. In the females fed on food treated with Pb the reduction of the number of egg pods was not remarkable. The hatchability of the eggs laid by Fl females was significantly reduced as compared to the control. The viability of the eggs laid by F 2 adults was somewhat decreased due to either a reduced number of egg pods or to a lower rate of hatchability, especially in the case of Cd. The treated adults frequently displayed weakness in their legs, difficulties in walking, tremors, and nervous movements. In 1% of the Fl adults, the wings were abnormally developed being outstretched and bent downward. The last instar nymphs hatching from eggs laid from FI adults in PbClz-treated soil failed to moult to adults.
Heavy metals occur in the environment in various concentrations. In the last decade, the amounts increased to levels which are toxic for many animals. Most of the heavy metals coming from factories, the use of pesticides, or fertilizers, are found in the soil. In the food chain, the heavy metals present in the soil (Brugger 1981; Schmidt et al. 1991) will be absorbed by the plants which are the food of grasshoppers and other herbivorous animals; they accumulate in their bodies and can influence various life parameters.
In plants, the mercury content is normally lower than 0.04 mg/kg, and the lead content less than 10 mg Pb/kg dry weight (Keller et al. 1986), but in polluted areas it can increase considerably (Scheffer and Schachtschabel 1982). In plants of a Finish Mirtillus-type forest, 0.08-0.60 mg Cd/kg of dry weight was found (Koski et al. 1988). Green plants are unable to take up much mercury from contaminated soil (Lodenius 1990); their content increased only to 0.08-0.12 mg Hg/kg if about 7 mg Hg/kg of dry soil were present, and in soils containing 27.5 mg Hg/kg the plants contained 0.32 mg/kg. In industrially loaded regions, the amount can increase up to 4.6 mg Hg/kg of dry weight (Rauter 1976). In the grasses of Canadian golf courses up to about 200 mg Hg/kg of dry weight were recorded. Toxic effects in plants (barley seeds) were observed in hydrocultures containing 1-4 mg HgC12/L, respectively more than 3 mg HgCl2/kg of dry plant weight (Schmidt, unpublished). The content allowed by FAO should not exceed 0.05 mg Hg/kg of fresh weight of food plants. For cadmium, only 0.1 mg/kg of fresh weight could be measured in wheat seeds. Kloke (1977) reported 0.05-0.2 mg Cd/kg of dry weight of plants. Vascular plants absorb metals from the soil water. Also the toxic effects on the roots are determined by the amount of soluble metal ions. In this sense, the amount of soluble metals is most important (Kojo and Lodenius 1989; Lodenius 1990). A contamination of the plants by the atmosphere is normally negligible. Only near roads highly frequented by traffic or near metal industries more than 40% of the cadmium plant content are absorbed by the leaves from the air (Scheffer and Schachtschabel 1982). The herbivorous animals, like most grasshoppers, can magnify heavy metals in their bodies and transfer them to higher trophic levels (Roberts et al. 1979). Very little is known about the influence of heavy metals absorbed by plants upon insects feeding on these plants. Therefore, the objectives of this study were to determine the long-term influence of heavy metals in diets on the development, reproduction, and viability of two consecutive generations of the acridid, Aiolopus thalassinus (Fabr.), which can be used as an indicator of environmental pollution (Schmidt 1986). Nymphal duration, adult body weight, percentage mortality and reproductive capacity were measured, as well as the
G.H. Schmidt et al.
376
distribution of the heavy metals in various insect organs. The toxic effects on some vital organs were investigated histologically. Some o f these can be used to assess the magnitude o f environmental pollution by chemicals, particularly in soil.
Material and Methods Rearing of the Test Insect The test insect, Aiolopus thalassinus (Fabr.) was collected at Sabaudia (Latina) and Cesenatico, both in Italy, near the Mediterranean Sea and bred continuously in the laboratory at Hannover (Schmidt 1981, 1986; Schmidt et al. 1991).
Food and its Contamination For the control experiments, the young hoppers (F~) from untreated parents were fed on wheat or barley seedlings loaded with
A~hives
of
E nvironmental
c o n t a ma nidn a t i o n | oxicology
© 1992 Springer-Verlag New York Inc.
Long-term Effects of Heavy Metals in Food on Developmental Stages of Aiolopus thalassinus (Saltatoria: Acrididae) Gerhard H. Schmidt*, Nabil M. M. Ibrahim**, and Mounir D. Abdallah** *Lehrgebiet Zoologie-Entomologie, FB Biologie, Universit/it Hannover, Herrenh~iuserStrasse 2, W-3000 Hannover 21, Federal Republic of Germany and **Department of Economic Entomology and Pesticides, Faculty of Agriculture, Cairo University, Giza, Egypt Abstract. Newly hatched F~ nymphs of Aiolopus thalassinus (Fabr.) were fed on food treated with various concentrations of HgCI2, CdC12, and PbC12 until the end of adult life. Toxicological observations were followed in the FI generation and in the F 2 generation derived from the heavy metal-loaded FI parents. The highest concentration of the heavy metals caused 100% mortality of the F1 adults within four weeks. The nymphal duration of the Fl and F 2 generations was significantly prolonged after Hg and Cd exposure, but the Fj of the group treated with lead was not affected. The fresh body weight of adults was significantly reduced in the F~ generation of most treatments and in the resulting untreated F 2. The lifespan of the F~ adults was shortened. In the F 2 generation, although the lifespan was somewhat longer, generally it was still shorter than that of the control adults. The mean egg number laid by F~ adults fed on food contaminated with Hg or Cd was decreased. This decrease was more pronounced in the case of Cd than Hg. In the females fed on food treated with Pb the reduction of the number of egg pods was not remarkable. The hatchability of the eggs laid by Fl females was significantly reduced as compared to the control. The viability of the eggs laid by F 2 adults was somewhat decreased due to either a reduced number of egg pods or to a lower rate of hatchability, especially in the case of Cd. The treated adults frequently displayed weakness in their legs, difficulties in walking, tremors, and nervous movements. In 1% of the Fl adults, the wings were abnormally developed being outstretched and bent downward. The last instar nymphs hatching from eggs laid from FI adults in PbClz-treated soil failed to moult to adults.
Heavy metals occur in the environment in various concentrations. In the last decade, the amounts increased to levels which are toxic for many animals. Most of the heavy metals coming from factories, the use of pesticides, or fertilizers, are found in the soil. In the food chain, the heavy metals present in the soil (Brugger 1981; Schmidt et al. 1991) will be absorbed by the plants which are the food of grasshoppers and other herbivorous animals; they accumulate in their bodies and can influence various life parameters.
In plants, the mercury content is normally lower than 0.04 mg/kg, and the lead content less than 10 mg Pb/kg dry weight (Keller et al. 1986), but in polluted areas it can increase considerably (Scheffer and Schachtschabel 1982). In plants of a Finish Mirtillus-type forest, 0.08-0.60 mg Cd/kg of dry weight was found (Koski et al. 1988). Green plants are unable to take up much mercury from contaminated soil (Lodenius 1990); their content increased only to 0.08-0.12 mg Hg/kg if about 7 mg Hg/kg of dry soil were present, and in soils containing 27.5 mg Hg/kg the plants contained 0.32 mg/kg. In industrially loaded regions, the amount can increase up to 4.6 mg Hg/kg of dry weight (Rauter 1976). In the grasses of Canadian golf courses up to about 200 mg Hg/kg of dry weight were recorded. Toxic effects in plants (barley seeds) were observed in hydrocultures containing 1-4 mg HgC12/L, respectively more than 3 mg HgCl2/kg of dry plant weight (Schmidt, unpublished). The content allowed by FAO should not exceed 0.05 mg Hg/kg of fresh weight of food plants. For cadmium, only 0.1 mg/kg of fresh weight could be measured in wheat seeds. Kloke (1977) reported 0.05-0.2 mg Cd/kg of dry weight of plants. Vascular plants absorb metals from the soil water. Also the toxic effects on the roots are determined by the amount of soluble metal ions. In this sense, the amount of soluble metals is most important (Kojo and Lodenius 1989; Lodenius 1990). A contamination of the plants by the atmosphere is normally negligible. Only near roads highly frequented by traffic or near metal industries more than 40% of the cadmium plant content are absorbed by the leaves from the air (Scheffer and Schachtschabel 1982). The herbivorous animals, like most grasshoppers, can magnify heavy metals in their bodies and transfer them to higher trophic levels (Roberts et al. 1979). Very little is known about the influence of heavy metals absorbed by plants upon insects feeding on these plants. Therefore, the objectives of this study were to determine the long-term influence of heavy metals in diets on the development, reproduction, and viability of two consecutive generations of the acridid, Aiolopus thalassinus (Fabr.), which can be used as an indicator of environmental pollution (Schmidt 1986). Nymphal duration, adult body weight, percentage mortality and reproductive capacity were measured, as well as the
G.H. Schmidt et al.
376
distribution of the heavy metals in various insect organs. The toxic effects on some vital organs were investigated histologically. Some o f these can be used to assess the magnitude o f environmental pollution by chemicals, particularly in soil.
Material and Methods Rearing of the Test Insect The test insect, Aiolopus thalassinus (Fabr.) was collected at Sabaudia (Latina) and Cesenatico, both in Italy, near the Mediterranean Sea and bred continuously in the laboratory at Hannover (Schmidt 1981, 1986; Schmidt et al. 1991).
Food and its Contamination For the control experiments, the young hoppers (F~) from untreated parents were fed on wheat or barley seedlings loaded with
