Introduction
Heavy metals are a large group of chemical elements that have toxic effects and are a rather widespread group at the present time, which is associated with an increase in technogenic impact on the environment [1].
Heavy metals entering the environment as a result of anthropogenic emissions have the ability to form complexes [2]. The most toxic is a combination of such elements as cadmium-lead-zinc, formed in the process of operation of non-ferrous metal smelting plants. Lead-copper and lead-zinc compounds are also toxic. However, the toxicity of these complexes is determined directly by the ratio of the proportions of metals included in the composition, the chemical form of the compounds of certain metals, as well as the susceptibility of living organisms to the effects of the complex [3]. In excessive accumulation in the environment can behave as toxicants and ecotoxicants [4].
The possibility of accumulating in plant, animal and human organisms is a serious threat of poisoning of a particular species of organism during its life activity. Toxic effects of heavy metals on humans are manifested when they enter his body through the food chain, disrupting the functioning of enzymes, heavy metals affect various organs, causing severe diseases [5].
At present, due to the numerous factors of environmental pollution, the procedures of environmental quality assessment using the reactions of model organisms to negative factors is an essential need [6].
For the most revealing result in the process of biotesting, the key factor is the choice of the test object [7].
The search for an alternative model for rodents resulted in the discovery of a universal model of G. mellonella, which is superior to mammals in terms of bioethical considerations and cost-effectiveness [8].
The larvae of G. mellonella have been shown to be a good physiological model for understanding the effects of toxic elements on living organisms in nature [9]. In additional, G. mellonella is used as a model in physiological, immunological, biochemical, and parasitological studies due to its rapid life cycle, larval size, and ease of cultivation under laboratory conditions [10].
Materials and methods
Breeding and maintenance of larvae. For mass rearing of the larvae of the large wax moth in laboratory conditions, special bioreactors equipped with lids with a fine-meshed soldered-in mesh were used. Bee honeycombs, flower pollen, and pollen with beeswax additives were used as the main substrate for cultivation. The optimum maintenance temperature range was 20-33°C with a relative humidity of 50-75%.
Measurements of heavy metals in larvae were carried out using a parallel-action atomic emission ICPE spectrometer parallel action.
Three samples with concentrations of Cd 1 g/l, Pb 10 g/l, Cd 1 g/l + Pb 10 g/l and a control sample were used to study the content of heavy metals in larvae on the ICPE instrument. The larvae were exposed for 24 hours, then the larvae were frozen for 24 hours and then dried on a filter paper under room conditions.
In a chemically clean ICPE beaker, the larvae were washed in 0.1 normal weak nitric acid and placed in a shaker for 5 minutes to wash off dirt and including unwanted metals from the surface of the larvae. The larvae were then placed on a filter funnel (a special funnel for ICPE treated with acid) and washed with deionized water.
The larvae were dried on filter paper. Then we weighed the beaker on an analytical scale, then placed the larvae in the beaker and weighed again. We placed the larvae in a 96 °C desiccator for 3 hours (3 hours counted only after heating to 96 °C).
After drying, we cooled it down. We weighed the larvae, then placed it back in the drying closet for two hours, took it out, and checked to see if the weight had changed.
When the larvae were completely dried, 10 ml of concentrated nitric acid was added and left overnight. Then, we put it in a sand bath for an hour to dissolve the larvae completely. 1 ml of hydrogen peroxide was added, and the resulting solution was filtered. The solution with the larvae was brought to 15 ml with deionized water and placed in the ICPE instrument.
Results
The experiment was conducted on 4 different samples of larvae – NaCl (control), Cd 1g/L, Pb 10 g/L, Pb + Cd (10 g/L + 1 g/L) using the device ICPE determined the content of trace elements after daily exposure to concentrations of heavy metals. The results of determination of trace elements on the device ICPE in different samples are shown in Table 1.
Table 1 – ICPE determination of trace elements, alkali and alkaline earth metals in various samples
Group/ Microelement |
NaCl (control) |
Cd 1 g/L |
Pb 10 g/L |
Pb + Cd |
Al |
2,2 |
2,2 |
2,3 |
4,5 |
As |
8,8 |
9,0 |
11 |
16 |
Cd |
0,00 |
7,5 |
0,02 |
18 |
Co |
0,14 |
0,25 |
0,26 |
0,25 |
Cr |
0,28 |
0,21 |
0,27 |
0,48 |
Cu |
5,3 |
4,2 |
3,7 |
4,1 |
Fe |
73 |
48 |
55 |
72 |
Mn |
1,1 |
0,55 |
0,74 |
0,75 |
Mo |
1,3 |
0,88 |
1,4 |
1,3 |
Ni |
1,5 |
0,60 |
0,94 |
0,05 |
Pb |
0,23 |
0,25 |
4,2 |
1,3 |
Se |
0,02 |
0,025 |
0,025 |
0,03 |
Sr |
3,4 |
0,70 |
3,4 |
7,4 |
Zn |
37 |
34 |
36 |
36 |
Ca |
2579 |
1799 |
4227 |
3240 |
K |
5768 |
5004 |
7742 |
5051 |
Mg |
1640 |
1759 |
2197 |
1600 |
Na |
560 |
536 |
591 |
434 |
Therefore, the above study of the content of cadmium and lead in larvae showed that under the complex influence of these metals, there is a high accumulation of one metal (cadmium) at the expense of the other (lead), while separately these metals have a moderate accumulation in the organism.
Conclusion
Studies have shown that the combined effect of two metals increases the accumulation of cadmium more than 2-fold under the influence of lead.
References
- Heavy Metals in the Environment: Origin, Interaction and Remediation, Heike Bradl, Elsevier, 2005, p. 282.
- Orlov, D.S. Ecology and protection of biosphere at chemical pollution: textbook / D.S. Orlov, L.K. Sadovnikova, I.N. Lozanovskaya. – Moscow : High School, 2002. – 334 p. – ISBN 506-0-0409-92.
- Baranova L.A., Dmitrenko I.V. Heavy metals in soils and plants around Tyumen Thermal Power Plant. – Text : electronic // Bulletin of the State Agrarian University of the Northern Trans-Urals. – 2013. – № 3 (22). – P. 19-22. – URL: https://elibrary.ru/item.asp?id=21539582 (date of access: 20.12.2022). – Access mode: Scientific electronic library eLIBRARY.RU.
- Ulakhovich, N. A. Ecotoxicants: a manual for the lecture course “Chemistry in Ecology” / N. A. Ulakhovich, M. P. Kutyreva, E. P. Medyantseva, S. S. Babkina. – Kazan: Kazan State University Press. – 2010. – P. 56. URL: https://repository.kpfu.ru/?p_id=20832 (date of reference: 20.12.2022). – Access mode: Catalog of scientific and educational resources of KFU. – Text : electronic.
- Qi X., Zhang Y., Chai T. Characterization of a novel plant promoter specifically induced by heavy metal and identification of the promoter regions conferring heavy metal responsiveness // Plant Physiol. 2007. V. 143.P. 50–59.
- Tsatsenko L. V. Biological soil testing : tutorial / L. V. Tsatsenko. – Krasnodar : KubGAU, 2019. – 90 p. – ISBN 978-5-00097-831-3. – URL: https://e.lanbook.com/book/171560 (date of reference: 20.12.2022). – Mode of access: Electronic library system Lan. – Text : electronic.
- Biotest analysis – an integral method of assessing the quality of Environmental Objects : teaching aid / A. G. Bubnov, S. A. Buimova, A. A. Gushchin, T. V. Izvekova. – Ivanovo : Ivanovo State University of Chemical Technology, 2007. – 112 p. – ISBN 5-9616-0237-0. – URL: https://e.lanbook.com/book/4489 (date of access: 20.12.2022). – Mode of access: Electronic library system Lan. – Text : electronic.
- Banville N, Browne N, Kavanagh K. Effect of nutrient deprivation on the susceptibility of Galleria mellonella larvae to infection. Virulence 2012; 3: p. 497-503.
- Dubovskiy, I. M. et al. Effect of the bacterial infection on the antioxidant activity and lipid peroxidation in the midgut of larvae Galleria mellonella L. (Lepidoptera, Pyralidae). Comp. Physiol. Biochem. 148(1), p. 1–5.
- Ramarao N, Nielsen-Leroux C, Lereclus D. The insect Galleria mellonella as a powerful infection model to investigate bacterial pathogenesis. J Vis Exp 2012; p. 70.