キクイタボヤに寄生する吸管虫の生活史

概要

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The life-history of a suctorian parasiting on living colonies of Botryllus primigenus was studied. Suctorians in the adult stage are found in ascidian zooids of stage 9 of phase B or C. They are arranged in a circle along the peripharyngeal band on the wall of the oral cavity. In summer months, several tens of parasites are found in a zooid. The parasite has no stalk and the form of the body is approximately oval, about 40×60μ large. The tentacles occur in two groups, each consisting of ten-odd tentacles. They end distally in a rounded expansion. The parasite has an elongated macronucleus. From late phase C to early phase D of the colony, the parasites escape from the zooid through the oral aperture to the test surface, where they lose the tentacles, develop the cyst and are embedded in the ascidian test. In late phase D, asexual reproduction takes place in the cyst by multiple endogenous budding. In phase A, excystment occurs; the suctorian larva with a polar circlet of cilia swims away from the cyst and enters the zooid of the next generation through the oral aperture just opened. The larva is oval in form and about 15×20μ in size. In late phase A, small suctorian adults are already found within the zooid. In colonies of Botrylloides violaceum and Symplegma reptans the parasite has not been found.
社団法人日本動物学会の論文
1970-10-15