RESUMO
Since several reports have indicated that cholinesterases (ChE) type and distribution is species specific and that in some species there is a relationship among gender, size and ChE activities, characterization has been suggested. The aim of the present study was to characterize the ChE present in head and muscle of Gambusia yucatana (using selective substrates and inhibitors) and to find its relationship with total length or gender. Results indicated that the ChE present in G. yucatana is an acetylcholinesterase (AChE) with high sensitivity to BW284C51 and an atypical smaller Km with butyrylthiocholine. Scatterplots indicated that there is no linearity between total length and AChE in male or female wild mosquitofish. There were no sex differences in AChE activities. Results indicated significant differences between a single collection site in the Yucatan peninsula and depurated organisms. This study emphasized the importance of characterizing ChE before usage in biomonitoring.