Serum “B” Esterases as a Nondestructive Biomarker for Monitoring the Exposure of Reptiles to Organophosphorus Insecticides

A field study was conducted to validate serum B esterases as nondestructive biomarkers (NDBs) in lizards. Serum butyrylcholinesterase (BChE) and carboxylesterase (CbE) activities were measured in lizards and four species of birds collected in an area of 0.5 ha sprayed with 0.36 kg a.i./ha of Folidol SE5 (5% parathion). Serum B esterase activities were determined in a total of 213 lizards (Gallotia galloti) and 81 birds of four species (Sylvia melanocephala, Serinus canaria, Parus caeruleus, and Erithacus rubecula) collected for 23 days after the spraying, A control group of 39 lizards and 58 birds was sampled before the spraying. No relationship was found between serum B esterases and sex or biometric parameters in all species. Inhibition of BChE (>40%) and CbE (>50%) activities was recorded in lizards 23 days after spraying. BChE activity was found to be more sensitive than CbE to inhibition by parathion. Inhibition of serum B esterase activities was recorded in only two bird species (S. melanocephala and S. canaria), but the number of individuals collected was much less than the lizards. The advantages and disadvantages of G. galloti as bioindicator of exposure to organophosphorus insecticides in the Canary Islands (Spain) are discussed in relation to birds commonly used for this purpose.