Toxicity of nitroaromatic explosives for the host-parasite system Tenebrio molitor–Gregarina spp. at different temperatures

Trinitrotoluene (TNT, 2,4,6-trinitrotoluene) is the most common explosive in ammunition from the last century, which continues to pollute ecosystems due to sunken ammunition in the seas (the Baltic Sea, the Adriatic Sea), remnants at former military training grounds, and leaks from ammunition factories. This study investigated the effect of TNT and its incomplete detonation products (o-NT, 2,4-DNT) on the relationship between Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae) and its parasites at temperatures of 21–23 °C and 26–28 °C. Six hundred T. molitor larvae (300 at each temperature) were divided into ten groups (control and three concentrations of three compounds: 30, 90, 270 mg/kg of substrate) at two temperatures (21–23 °C, 26–28 °C). During the 5-day exposure, mortality, body weight changes and the intensity of parasitic invasion by three species of Gregarina were assessed. The results showed concentration-dependent toxicity with a differentiated gradation: TNT (most toxic) > o-NT > 2,4-DNT (least toxic). At a maximum concentration of 270 mg/kg and a temperature of 26–28 °C, mortality was 40% for TNT, 27% for o-NT, and 10% for 2,4-DNT. Nitroaromatic compounds did not affect the intensity of Gregarina spp. parasitic invasion for 2,4-DNT or TNT, while for o-NT parasite counts increased with concentration but remained within the range spanned by the control groups. At the same time, exposure to nitroaromatic compounds induced premature transformation of larvae into pupae – approximately one in ten larvae in the experimental groups underwent metamorphosis, while in the control groups there was no transformation (p = 0.002). Elevated temperature (26–28 °C) increased the toxicity of nitroaromatic compounds (p = 4.76×10⁻⁴) and reduced the number of parasites by 26–36% compared to lower temperatures.