Brain Cholinesterase Activity and Its Inheritance in Cattle Tick (Boophilus Microplus) Strains Resistant and Susceptible to Organophosphorus Acaricides

Abstract

Brain acetylcholinesterase (AChE) activities of individual cattle ticks, B. microplus, of an organophosphorus-resistant strain were compared with those of a standard reference strain. When measured by a histochemical-densitometric method on photographic transparencies and by a biochemical method, brains from homozygous resistant adult female ticks had about 12% of the AChE activity of brains from homozygous susceptible ticks_ Brains of hybrid adult females had about 78%, histochemically and biochemically, of the AChE activity of their susceptible parents, indicating that low AChE activity was incompletely recessive although the associated resistance to organophosphorus compounds had been shown previously to be incompletely dominant_