Effect of different doses of selenium in the nutrient medium on California worm reproduction

Abstract

Worms have a unique ability to accumulate trace elements in their body from the substrate, which creates the preconditions for obtaining a protein-mineral supplement with high metal content in organic form. Selenium occupies a special place among the seventeen trace elements that are recognized as vital for the human body, animals and birds. Selenium, present in a body in small quantities, performs essential functions: catalytic, structural, regulatory. Selenium has antioxidant, immunostimulatory, anticancer, antimutagenic, adaptogenic, antiviral and radioprotective properties. The aim was to conduct experimental studies on the reproduction of worms, weight gain and selenium accumulation in their body depending on the content of this element in the nutrient medium. To experiment, we formed 54 micro-beds. The size of such bed was 0.5 x 0.7 m. We placed 11.0 kg of a worm nutrient medium in each microbed and divided into the six groups (one control and five experimental) with nine. The nutrient medium contained selenium, natural backround; additional trace element was not introduced. In the experimental microbeds, selenium 1; 2; 4; 8 and 16 mg/kg of the nutrient medium was added in the form of sodium selenite Na2SeO3•5 H2O. Eighty mature hybrids of red California worms were populated in each microbed. At the end of the 110-day experiment, the number of worms was counted in all microbeds, and average worm biomass samples were taken to determine the selenium content. The atomic absorption spectrophotometry determined selenium content in the worm biomass on a Shimadzu AA-6650 (“Shimadzu”, Japan). We found that the optimal dose of selenium is 4 mg/kg of medium nutrient weight, while the number and weight of adult worms increases by 86.7% and by 93.2%, and immature ones by 60.2% and by 63.9% as compared to the control. The negative effect on the vermiculture by Selenium16 mg/kg dose of the nutrient medium, decreases in adult worms by 38% compared with control microbeds. When growing worms on a nutrient medium with additional application of selenium with doses of 1 mg/kg, 2, 4, 8 and 16 mg/kg of the substrate, the content of this element in the dry vermiculture mass increases, respectively, by 2.4; 4.4; 8.5; 14.9 and 26.8 times. We also established a direct staleness between selenium content in the nutrient medium and that in a dry mass of the vermiculture.