Swimming velocity, avoidance behavior and biomarkers in Palaemon serratus exposed to fenitrothion

The aim of this study was to develop two behavioral tests (swimming velocity and avoidance behavior) specific for the common prawn, Palaemon serratus, and to investigate the effects of sublethal concentrations of fenitrothion on behavior and on several biomarkers. In a first bioassay, mortality was investigated in prawns exposed during 96 h to concentrations of fenitrothion ranging from 39 to 40000 ng L(-1). The effects on swimming velocity and biomarkers were determined in prawns exposed to the sub-lethal concentrations of fenitrothion (from 39 to 625 ng L(-1)). A specific newly bioassay was developed to assess the capability of prawns to avoid the toxicant (avoidance test). Finally, in order to determine the effects on biomarkers during the avoidance test, prawns were collected at different times of exposure (30, 60, 90 and 120 min). Results showed that prawns exposed to the sub-lethal concentrations of fenitrothion exhibited a significant inhibition of swimming velocity with a LOEC of 313 ng L(-1). A significant inhibition of both eye AChE (LOEC=78 ng L(-1)) and muscle ChE (LOEC=156 ng L(-1)) activities were also observed. Results from the avoidance test indicated that animals significantly avoided fenitrothion (78 ng L(-1)). However, this capability was not observed in prawns exposed to 156 ng L(-1) fenitrothion. Prawns exposed to fenitrothion showed alterations in enzymes involved in the production of energy (LDH and IDH) possibly in an attempt to cope with additional energetic demands. Impairment of locomotion and avoidance may lead to alterations at the population level. Thus, the present behavioral tests can be useful as ecologically relevant tools for ecological risk assessment.