Acute toxicity of lead on the survival of Macrobiotus hufelandi (Eutardigrada: Parachela: Macrobiotidae)

Aquatic ecosystems are constantly exposed to heavy metals and various chemicals that cause toxic effects on living organisms with increasing human activity. The tardigrades can survive in extreme conditions, in the present study, their ability to survive in various concentrations of toxic metal (lead) was evaluated. The acute mean lethal toxicity (LC50) indicates toxic effect assessment on organisms after exposure to heavy metals. This study assessed for the first time the LC50 values of lead toxicity after 24, 48, 72, and 96 hours of exposure in the tardigrade species Macrobiotus hufelandi are presented, based on animal mortality. The tolerance of Mac. hufelandi to lead is quite high in the 24 hours (LC50: 94.651 mg/L). The LC50 was estimated as 43,540 mg/L after 48 hours of exposure, and the mortality rates increased depending on time and concentration, LC50 was estimated as 22,344 mg/L after 72 hours, and calculated as 8,048 mg/L after the 96th hour. In addition, for the differences in the number of tardigrade deaths over time between groups (pairwise) Friedman's test findings were found between 24h-96h, 48h-96h and 24h-72h, respectively. The results demonstrate that tardigrades can be appropriate invertebrate models to provide insights into heavy metal tolerance research.