THE LIZARD GALLOTIA-GALLOTI AS A BIOINDICATOR OF ORGANOPHOSPHORUS CONTAMINATION IN THE CANARY-ISLANDS

The aim of this study is to propose a bioindicator organism, the lizar d Gallotia galloti, and a nondestructive biomarker assay, utilising se rum butyrylcholinesterase, for the assessment of the toxicological imp act of organophosphorus (OP) insecticides in the Canary Islands. Labor atory and field studies were performed using the OP insecticide Trichl orphon. In the laboratory study, experimental groups of Gallotia gallo ti were treated with 5, 50 and 100 mg/kg of Trichlorphon, respectively , and after 24 h the following enzyme activities were assayed: brain a cetylcholinesterase (AChE), serum butyrylcholinesterase (BChE), micros omal carboxylesterase (CbE) and microsomal 7-ethoxyresorufin dealkylat ion (EROD). BChE activity was monitored in two groups of lizards treat ed with 50 and 100 mg/kg of Trichlorphon, respectively, for a period o f 21 and 31 days after treatment. In the field study, BChE activity wa s detected in Gallotia galloti specimens, 24 and 48 h after treatment of an experimental area with 10 kg/ha of Dipterex sp80 (80% Trichlorph on). Three conclusions can be drawn. (1) Gallotia galloti has the feat ures of an ideal bioindicator: high sensitivity to OPs and extremely s low recovery of serum BChE with respect to other vertebrate species; t his properly extends the temporal application of this biomarker in fie ld studies. (2) A high correlation was found between the destructive b iomarker brain AChE and the nondestructive biomarker serum BChE, 24 h after treatment. (3) The results of the field study show the relative 'non-toxicity' of Trichlorphon for nontarget organisms, such as lizard s, at the average concentrations used in agriculture.