# The Effect of Ammonia on the Host–Parasite System Tenebrio molitor at Different Temperatures

## TL;DR

Ammonia pollution harms mealworm larvae and their gut parasites, with parasitic counts being more sensitive indicators than body weight.

## Contribution

The study reveals that parasitological parameters are more sensitive indicators of ammonia toxicity than physiological ones in mealworms.

## Key findings

- Higher ammonia concentrations increased larval mortality and reduced parasite abundance.
- Parasite counts were more sensitive to ammonia stress than body weight measurements.
- Temperature did not alter ammonia toxicity in the tested range (21–28 °C).

## Abstract

This study examined how ammonia pollution affects mealworm larvae (Tenebrio molitor) and their gut parasites (Gregarina species) at two temperatures. Ammonia enters ecosystems through agricultural activities, industrial accidents, and chemical plant emissions, posing risks to invertebrates. We exposed 150 larvae to different ammonia concentrations (0–4000 mg/kg substrate) at 21–23 °C and 26–28 °C for 10 days, measuring survival, body weight changes, and parasite numbers. Higher ammonia concentrations increased larval mortality (up to 60%) and reduced parasite abundance, but surprisingly, temperature within the tested range did not alter these toxic effects. Parasite counts proved more sensitive to ammonia stress than body weight measurements, with differences detected at lower concentrations. These findings suggest that parasitological parameters could serve as early warning indicators of sublethal ammonia toxicity. The results are relevant for industrial mealworm production, where ammonia accumulates from organic waste decomposition, and for understanding how environmental pollutants affect insect–parasite relationships in agricultural ecosystems.

Ammonia (NH3) is an environmental pollutant that enters ecosystems as a result of agricultural activities, industrial accidents, leaks of ammonia-based rocket fuel, and explosions at chemical plants. Temperature changes can alter the toxicity of ammonia to invertebrates. This study investigated the effect of ammonia on the relationship between Tenebrio molitor Linnaeus, 1758 (Coleoptera: Tenebrionidae) and its parasites at temperatures of 21–23 °C and 26–28 °C. We used 150 T. molitor larvae, which were divided into five groups of ammonia concentrations (0–4000 mg NH3/kg of substrate) at two temperatures (21–23 °C, 26–28 °C). During a 10-day exposure, mortality, body weight changes, and the intensity of parasitic invasion by three species of Gregarina were assessed. The results showed a concentration-dependent effect of ammonia on the physiological state and parasitic systems of T. molitor (body weight changes: p = 2 × 10−16; intensity of parasitic invasion: R2 = 0.13–0.87), while mortality increased from 0% in the control groups to 40–60% at maximum concentration. Contrary to expectations, temperature did not alter the toxicity of ammonia in the studied range of 21–28 °C (all p > 0.18). Parasitological parameters showed higher sensitivity to ammonia stress compared to physiological indicators, forming 4–5 concentration groups versus 2 groups for body weight changes. The observed absence of temperature-dependent changes in ammonia toxicity in the range of 21–28 °C contrasts with the known effects in aquatic invertebrates and may reflect the physiological characteristics of terrestrial insects. The higher sensitivity of parasitological parameters confirms their suitability as indicators of sublethal toxicity for monitoring ammonia pollution in industrial insect breeding systems.