[The ontogenetic variability of the morphometric traits of 2 species of ixodid ticks in the genus Rhipicephalus].

Variability of 10 morphometric characters at all phases was investigated on laboratory cultures of R. turanicus and R. bursa. It has been shown that variability increases from phase to phase. R. turanicus nymphs of both sexes differ in the length of gnathostoma and length of the 1st tarsus. In nymphs of R. bursa sexual dimorphism manifests itself on 8 characters, in all cases sizes of organs are greater in female nymphs. Besides, engorged female nymphs are reliably greater than male ones in length and mass of the body. Mature females and males of R. bursa also reliably differ in the total body length as well as in sizes of all examined structures. Females and males of R. turanicus do not differ in body length but differ in 9 other morphometric characters. Correlation analysis of characters was carried out individually for each phase and sex. Correlation coefficient between characters are most low in larvae. In R. turanicus male and female nymphs the coefficients are close. In R. bursa female nymphs correlation coefficients are noticeably lower than in male ones. The level of independence of characters in female nymphs defines the degree of manifestation of sexual dimorphism at this phase: the closer the links between characters, the lesser the number of characters revealing sexual differences. Coefficients of correlation of characters coincide in males of both species. In females of R. turanicus they are lower than in males that determines the strengthening of sexual dimorphism at the phase of imago.(ABSTRACT TRUNCATED AT 250 WORDS)