Abstract
Cytokinetic analyses were carried out on the testis of the American dog tick ( Dermacentor variabilis) nymph during the developmental period which follows attachment to the host and feeding. The spermatogonial cell division cycle in vivo was determined: Tc, 22.8 hr; S, 6.7 hr; G 1, 8.2 hr; G 2, 4.0 hr; P, 3.5 hr; M, 0.4 hr. Histological techniques were used to determine the timing of spermatocyte differentiation and accumulation. This accumulation is markedly biphasic, occurring as two distinct waves during the developmental period. Models of germarial zone division-induction are presented, and the theoretical population curves generated by these models compared to the empirical data. Development of a previously-unreported secretory tissue in close association with the nymphal testis is described, and some correlations between germarial division activity and endocrine events known from related species presented.
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