Resumen

Freshwater ecosystems are under increasing pressure from human activities, with pesticide contamination posing a significant threat to aquatic biodiversity. This study evaluates the sublethal effects of the neonicotinoid insecticide thiamethoxam (THM) on the locomotion of juvenile and adult Xiphocaris elongata, a keystone species in Puerto Rican streams that plays a critical role in organic matter processing and nutrient cycling. The research hypothesizes that exposure to higher concentrations of thiamethoxam and for longer periods will impair shrimp locomotion, with juveniles exhibiting greater sensitivity compared to adults.​

Shrimp were exposed to THM at concentrations of 43.2, 86.4, and 168.5 µg/L, alongside a control group. Locomotion was recorded for 15 minutes after exposure and again after 24 hours, measuring active time, distance traveled, and average speed using Loligo® Software. This experimental design assessed short-term and prolonged effects on behavior.​

A multivariate analysis of variance revealed significant effects of life stage, exposure time, and THM concentration on locomotive behavior. Juveniles displayed increased activity at low concentrations (43.2 µg/L) but showed a steep decline at higher doses, indicating heightened sensitivity. Adults exhibited greater tolerance at moderate concentrations (86.4 µg/L) but also showed reduced activity at the highest concentration (168.5 µg/L).​

Results demonstrate that THM exposure disrupts normal locomotive behavior, particularly in juveniles. These findings highlight the ecological risks of pesticide contamination in freshwater systems and emphasize the urgent need for stricter pesticide regulation to protect sensitive aquatic species and preserve ecosystem balance.

Palabras claves: Xiphocaris elongata, locomoción, neonicotinoides, thiamethoxam, ecosistemas de agua dulce