We established an experimental system, using an integrative biology "Planarian asexual reproduction examples," to analyze the mechanism in the planarian, Dugesia ryukyuensis Kobayashi et al.
Worms of exclusively asexual clone OH strain of the species gradually develop ovaries, testes and other sexual organs, then copulate and eventually lay cocoons filled with fertilized eggs, if they are fed with sexually mature worms of Bdellocephala brunnea an exclusively oviparous species.
This suggests the existence of a sexualizing substance s in sexually mature worms. Random inbreeding of experimentally sexualized worms acquired sexuals produces an F1 population of spontaneous sexuals innate sexuals and asexuals in a ratio of approximately 2: All regenerants from various portions of innate sexuals Planarian asexual reproduction examples sexuals.
In the case of acquired sexuals, head fragments without "Planarian asexual reproduction examples" organs regenerated into asexuals though regenerants from other portions became sexuals. It is also shown that sexuality in acquired sexuals is maintained by the putative sexualizing substance s of their own.
The sexualization is closely coupled with cessation of fission, and the worms seem to have an unknown way of controlling the karyotype. Our integrative approach integrates multiple fields of study, including classic breeding, regeneration, and genetics experiments, as well as karyotyping, and biochemical and molecular biological analyses; none of which would have revealed much about the intricate mechanisms that regulate sex and fission in these animals.
Asexual reproduction in a strict sense, namely amixis, is the reproduction without meiosis and syngamy. Most of those that can asexually reproduce convert their reproductive modes from asexual to sexual reproduction, and vice versasometime in their life or in some phase of life cycle, and those like bdelloid rotifers that reproduce exclusively asexually are very rare Welch and Meselson, However, the mechanisms underlying the switch of reproductive modes in metazoans remain hardly known.
It is known that some planarians, like those in the genus Dugesiacomprise at least three races with respect to the reproductive mode: In the asexual race, worms reproduce by fission without sexual organs. In the sexual race, worms have hermaphroditic sexual organs, and copulate and then lay cocoons filled with several fertilized eggs. They are not likely to fission. In the physiological race, worms convert between asexual and sexual Planarian asexual reproduction examples seasonally.
In these planarians, the asexual race switches from asexual to sexual reproduction by being fed with sexually mature worms of the same, as well as different, species Grasso and Benazzi, ; Benazzi and Grasso, ; Sakurai, This result suggests that sexually mature planarians contain a sexualizing substance s of poor species-specificity. The OH strain of Dugesia ryukyuensis is an exclusively asexual clone established by Dr. Ishida of Hirosaki University from a single worm collected in Okinawa, Japan in We established an experimental system for the sexualization in the OH strain by feeding them with Planarian asexual reproduction examples mature worms of Bdellocephala brunneaan exclusively oviparous species Kobayashi et al.