Biochemical studies of tick embryogenesis DNA, RNA, haemoprotein, guanosine and guanine in developing eggs of Hyalomma dromedarii

Abstract

The changes in the amounts of both DNA and RNA in newly oviposited Hyalomma dromedarii eggs exhibited a lag period of nine and six days, respectively when little increase occurred, after which they increased rapidly and then remained at a high level until hatching. The amount of DNA after the lag period was much higher than RNA throughout the rest of the time studied. Guanine could not be detected until day 15 after oviposition. However, guanosine could be detected in the newly oviposited eggs and was present until day 21. This suggests de novo biosynthesis of guanine in developing eggs and the induction of specific nucleosidase catalyzing the conversion of guanosine to guanine. Total protein content of the eggs remained unchanged. Two major (I and II) and two minor (II and IV) haemoprotein fractions were separated on DEAE-cellulose columns from the newly oviposited eggs. Fraction I was detected only up to day 3. Changes in the concentration of fractions II and III during embryogenesis suggest their interconversion.