Acute effects of deltamethrin on swimming velocity and biomarkers of the common prawn Palaemon serratus

The main purpose of the present study was to investigate the effects of deltamethrin on biomarkers and behavior of Palaemon serratus (common prawn), since this attempt to link different levels of biological organization will allow determining which biomarkers might be ecologically relevant and will be useful to complement the information about the effects of pesticides by using behavioral parameters. Therefore, parameters of liver antioxidant status, energy metabolism and neurotransmission were determined in different tissues of the common prawn and used to assess the effects at sub-individual level, whereas swimming velocity was used to assess the effects at the individual level. It was also investigated if the swimming velocity can be used as an endpoint in ecotoxicology bioassays and if it can be as sensitive as biomarker endpoints. Swimming velocity was significantly reduced in prawns exposed to deltamethrin, showing a lowest observed effect (LOEC) of 0.6ngL⁻¹. Eye acetylcholinesterase (AChE) activity was significantly increased in prawns exposed to 0.6, 1.2 and 2.4ngL⁻¹ deltamethrin, whereas muscle cholinesterase (ChE) activity was significantly increased in prawns exposed to 19 and 39ngL⁻¹. On the other hand, lactate dehydrogenase (LDH) activity was significantly increased in muscle of prawns exposed to 0.6, 1.2, 2.4, 4.9ngL⁻¹ deltamethrin, showing that organisms were requiring additional energy, but probably using it for detoxification processes rather than locomotion, since swimming velocity was inhibited. Glutathione S-transferase (GST) activity was significantly increased in the digestive gland of common prawn exposed to 19 and 39ngL⁻¹ deltamethrin. Catalase (CAT) activity was significantly increased in digestive gland of prawn exposed to 19ngL⁻¹ deltamethrin. However, CAT activity decreased in digestive gland of prawn exposed to 39ngL⁻¹, suggesting an antioxidant defense system failure concomitant with high levels of lipid peroxidation. Thus, global results showed that decreased swimming velocity was not associated with cholinesterase inhibition. In fact, the impairment of swimming velocity may be due to allocation of energy for detoxification and antioxidant protection instead of swimming activity. The present study showed that swimming velocity could be used as an ecologically relevant tool and a sensitive endpoint to assess and complement the study of pesticide effects on marine organisms.