Anti-
vitellin IgG directed against Dermacentor variabilis egg
vitellin was used in
sodium dodecyl sulfate polyacrylamide (SDS-PAGE) gradient gel immunoblots to detect the presence of
vitellin and its precursor,
vitellogenin, in the organs of feeding adults and in the immature stages of this tick.
Vitellin polypeptides were found in the egg, larvae, nymph, and in the unfed adult stages of both sexes.
Vitellin polypeptides were first detected in the ovary of mated females during the rapid-engorgement feeding period. These
polypeptides were also present in the ovaries of ovipositing females, unmated females fed for extended periods, and fed unmated females that were detached from the host and held for 12 h before dissection. The same anti-
vitellin antibody was used in immunoblots to monitor the appearance of
vitellogenin in the organs and hemolymph of female ticks. Immunoreactive
peptides of
vitellogenin were found in the fat body, midgut, and hemolymph of pre-rapid-engorging mated and unmated females. These
polypeptides were not found in fed males nor in Malpighian tubes of feeding or ovipositing females. Our data supported the following conclusions: 1) presence of immunoreactive
vitellogenin in the adult female fat body, hemolymph, and midgut was dependent upon feeding; 2) in mated feeding females, we could not detect the uptake of
vitellogenin by the ovary until rapid engorgement; 3) in unmated females, vitellogenesis did not begin unless prolonged feeding occurred; and 4) during the early developmental stages of this tick,
vitellin served as an embryonic nutrient reserve and as a reserve against
starvation between feedings.