Kinetics of proglottid formation, maturation and shedding during development of Hymenolepis nana

Growth of Hymenolepis nana in mice is analysed by identifying designated stages of proglottid maturation in the strobila, and by determining the numbers of proglottids between them and the posterior terminus of the worm, as a function of time after cysticercoid infection. The proglottid maturation rate was fairly constant between stage A (onset of the somatic primordium formation) and stage B (first appearance of sperms in the seminal vesicle), but gradually fell after stage B, during pre-patent development of the worm. The actual rate of proglottization during this period coincided well with that estimated from the number of proglottids between stages A and B on an assumption of a certain maturation rate. This procedure is extended to estimate the rates of proglottid formation and shedding during later development. It is deduced that the absolute rate of proglottization increases until day 12, gradually decreasing afterwards, and that from 2300 to 2800 proglottids are shed by day 20, until which from 4000 to 4500 proglottids have passed stage A. It is shown that the proportionate increase of the gravid region in older worms depends not only on a decrease in the rate of proglottization, but also on the prolonged period during which proglottids stay in the strobila.