Quantitative studies on the growth and multiplication of tetrathyridia of Mesocestoides corti Hoeppli, 1925 (Cestoda: Cyclophyllidea) in rodents

Abstract

Tetrathyridia multiply by splitting scolices, regenerating their median portions, and increasing in length. Pinching off of the caudal end of the daughter tetrathyridium leaves at the proliferative side of the parental organism a stump with one or two excretory bladders. Such stumps may later bud off acephalic fragments, but do not regenerate scolices. Long posterior portions of parental organisms with several stumps may separate from the scolex-carrying anterior portion and become acephalic. Such fragments do not produce scolices and later degenerate. Polycephalic forms, with up to 22 scolices, occur mostly in hosts with long-standing infections (over 100 days). Such forms transplanted into a new host break into the usual tetrathyridia plus large branching acephalic portions. Separation of the oldest parental scolex, situated at the non-proliferative side of the tetrathyridium, transforms this side into a proliferative side. In normal tetrathyridia, each new daughter tetrathyridium splits off anterior to the stump left by the previous one. If the posterior portion was not cast off, the number of stumps indicates the number of daughter tetrathyridia produced.In mice injected with 0.03 cm3 of tetrathyridia, and dissected 50 days post infection, the total volume of intraperitoneal population varied from 0.15 in deer mice to about 1.0 cm3 in LDF1 males. Increase in biomass was faster in male hosts than in females.