Sulphydryl Content of the Embryos of the Australian Cattle Tick

Abstract

Thompson and Johnston¹ reported that the total sulphydryl content of embryos of an arsenic-resistant strain of the South African blue tick (Boophilus decoloratus) was approximately twice that of an arsenic-susceptible strain. Harington² afterwards examined larvæ of these strains and reported that the cystine–cysteine, glutathione and total free sulphydryl values were significantly higher in the arsenic-resistant strain. To establish whether the same relation as reported by Thompson and Johnston held in Boophilus microplus, investigations were carried out with a strain from northern New South Wales, larvæ of which exhibited a 10.7 fold (9.3–14.0; P < 0.001) degree of resistance to arsenic in comparison with those of the susceptible Yeerongpilly reference strain. Adults of both strains were maintained at 30° C. and the ticks removed from the containers four days after oviposition had commenced. Daily thereafter throughout incubation four samples of eggs were taken and their total sulphydryl content determined by a nitroprusside method³, using as a standard a solution of glutathione freshly prepared each day.