Effects of cypermethrin as a model chemical on life cycle and biochemical responses of the tropical stingless bee Meliponula bocandei Spinola, 1853

Abstract

The tropical stingless bee, Meliponula bocandei Spinola, 1853 is an important pollinator in West Africa but there is no study on the effect of pesticides on this species. This study assessed the effects of cypermethrin, a common pyrethroid on survival, taste (sucrose sensitivity), and biochemical responses of M. bocandei. The biochemical markers were superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase (GST), reduced glutathione [GSH]), and acetylcholinesterase [AChE]) as well as glucose, trehalose and total protein concentrations. Test temperature was optimized by acclimatizing adult worker bees collected from a pristine natural colony to different temperature regimes in the laboratory and fed with sucrose solution. The optimized temperature (22°C) for survival and sucrose consumption was adopted for the toxicity test. The 24–48 h oral lethal dose (LD50) and 24–96 h indirect contact lethal concentration (LC50) of cypermethrin on the bees was in the range of 0.66–0.76 µg/ml and 92.24–223.69 µg/ml respectively. Also, the overall PER response reduced below 50% in bees that were orally exposed to high doses of cypermethrin. There was significant decrease in glucose, trehalose, total protein and GSH concentrations in bees when compared with the control. Also, significant alterations were observed in SOD, CAT, GST and AChE activity for both oral and contact exposure pathways. In conclusion, cypermethrin modulated the activities of biomarkers of oxidative stress and altered the level of energy metabolites in the bees.