KOBAYASHI, KAZUYA; ARIOKA, SACHIKO; MATSUMOTO, MIDORI; HOSHI, MOTONORI*; KEIO UNIVERSITY; KEIO UNIVERSITY; KEIO UNIVERSITY; KEIO UNIVERSITY: Reproductive Mode of the Inbred Offspring of Aquired Sexuals in the Planarian Dugesia ryukyuensis

Many animals switch their reproductive mode, but little is known on the molecular mechanism of the switch. The planarian, Dugesia ryukyuensis, has three populations in terms of reproductive mode; exclusively asexuals, seasonal switchers, and exclusively sexuals. The OH strain of the species is an exclusively asexual clonal one originated from a single exclusively asexual worm. If the worms of this strain are fed with sexually mature worms of the same or different species of planarians, they become sexualized. Inbreeding of thus sexualized worms, the acquired sexuals, produced an F1 population of both the asexuals and the innate sexuals that develop spontaneously into sexual worms. Some differences between the two types of offspring will be discussed.