Effects of formalin on some biomarker activities of earthworms pre-exposed to temephos

Despite its negative effects, formalin has been often used for the expulsion of earthworms due to its high efficiency; however it is not known whether it will affect any significant measurable molecular processes in sampled earthworms. The aim of this research was to investigate effects of formalin on the activities of chosen molecular biomarkers in Eisenia andrei earthworms previously exposed to temephos. Additionally, the inhibitory effect of temephos, hitherto evaluated only on laboratory-bred earthworm species, was confirmed on two earthworm species obtained from their natural environment – Dendrobaena octaedra and Lumbricus rubellus. Earthworms were first exposed to the sub-lethal concentration of temephos for 2 h and then to formalin 15 min in order to simulate the sampling procedure. Besides acetylcholinesterase (AChE) inhibition – a known biomarker of exposure to organophosphate insecticides – the concentration of oximes and the activities of catalase (CAT) and efflux pump were measured. Results showed that in all species temephos caused inhibition of AChE and CAT activity. Exposure of E. andrei to formalin caused inhibition of AChE, however after post-exposure to formalin for 15 min significant increase in AChE activity was recorded. Similar results were obtained with the measurement of oximes concentrations. Exposure to only formalin and combination of temephos (2 h) and formalin (15 min) led to an increase in the CAT activity. The obtained results showed that exposure to formalin during the sampling could affect measured molecular biomarkers and also may change effects caused by exposure to temephos.