RHIPICEPHALUS-SANGUINEUS AND R-TURANICUS (ACARI, IXODIDAE) - CLOSELY-RELATED SPECIES WITH DIFFERENT BIOLOGICAL CHARACTERISTICS

Life cycle parameters of 2 closely related tick species, Rhipicephalus sanguineus Latreille and R. turanicus Pomerantsev, were studied under laboratory conditions. Both Rhipicephalus, which have small adults, d emonstrated the same adaptations as large tick species inhabiting dese rts and semideserts: high reproductive rate, decrease in egg size, and an increase in interstage growth to compensate for the smaller size a t birth. Pronounced quantitative differences between both species were discerned in relation to these adaptations. Female R. turanicus produ ced twice as many eggs as R. sanguineus which was facilitated by the g reater amount of blood engorged by females and by the smaller egg weig ht in R. turanicus as compared with R. sanguineus. In all developmenta l stages, the weight increase from unfed to fed ticks was greater in R . turanicus than in R. sanguineus (23% higher in larvae, 118% in nymph s, and 26% in females). The increase in weight in R. turanicus from th e unfed larva (0.013 mg) to the unfed female (3.31 ma) was 254-fold, a nd in R. sanguineus it was 127-fold (from 0.021 to 2.54 mg). In nympha l R. turanicus, the higher density and the greater height of the dorsa l epicuticular folds, as well as procuticular indentations found insid e the folds allow this tick to stretch its alloscutum during blood eng orgement to a greater extent than R. sanguineus. The rates of blood in gestion (for nymphs and females), egg maturation, and metamorphosis we re 1.1-1.7 times greater in R. turanicus than in R. sanguineus. A life cycle strategy with both a higher reproductive rate and faster develo pment in R. turanicus may be explained by its greater dependence on en vironmental factors than that in R. sanguineus.