Behavioral and energetic impacts of sublethal cypermethrin exposure on palaemonid prawns

This study aimed to assess the effects of sublethal environmentally relevant concentrations of the pyrethroid insecticide cypermethrin (Cyp) on the behavior of two prawn species inhabiting Pampean lowland streams: Macrobrachium borellii and Palaemon argentinus. To this end, we conducted laboratory assays of 96 h to evaluate the effects of Cyp (concentration of 0.006 µg Cyp/L to M. borellii and 0.0006 µg Cyp/L to P. argentinus) on the reproductive behavior (pleopod beat rate) of vitellogenic and ovigerous females of both species, as well as on their energy demands. Additionally, we assessed the impact of sublethal Cyp concentrations on the locomotor activity and feeding behavior of M. borellii. The results showed that Cyp-exposed females of both species exhibited an increased pleopod beat rate and reduced glycogen content in the abdominal muscles. Probably, the intensified activity of pleopods increased the female energy demands, which were met by the glycogen reserves in the abdominal muscles. Cyp also reduced the locomotor activity of prawns, decreasing the time, distance, and speed of their swimming and walking, which led to an increase in rest time. Regarding feeding behavior, Cyp exposure did not affect the time M. borellii took from food detection to ingestion; however, Cyp-exposed prawns consumed less food than control prawns. These results confirm that Cyp induces significant behavioral changes in these two prawn species inhabiting Pampean streams. Alterations in these life-history traits may negatively impact prawn fitness, ultimately affecting population dynamics and the ecological functions of Pampean environments.