, Volume 123, Issue 3, pp 265–272 | Cite as

Triploid planarian reproduces truly bisexually with euploid gametes produced through a different meiotic system between sex

  • Ayako Chinone
  • Hanae Nodono
  • Midori MatsumotoEmail author
Research Article


Although polyploids are common among plants and some animals, polyploidization often causes reproductive failure. Triploids, in particular, are characterized by the problems of chromosomal pairing and segregation during meiosis, which may cause aneuploid gametes and results in sterility. Thus, they are generally considered to reproduce only asexually. In the case of the Platyhelminthes Dugesia ryukyuensis, populations with triploid karyotypes are normally found in nature as both fissiparous and oviparous triploids. Fissiparous triploids can also be experimentally sexualized if they are fed sexual planarians, developing both gonads and other reproductive organs. Fully sexualized worms begin reproducing by copulation rather than fission. In this study, we examined the genotypes of the offspring obtained by breeding sexualized triploids and found that the offspring inherited genes from both parents, i.e., they reproduced truly bisexually. Furthermore, meiotic chromosome behavior in triploid sexualized planarians differed significantly between male and female germ lines, in that female germ line cells remained triploid until prophase I, whereas male germ line cells appeared to become diploid before entry into meiosis. Oocytes at the late diplotene stage contained not only paired bivalents but also unpaired univalents that were suggested to produce diploid eggs if they remained in subsequent processes. Triploid planarians may therefore form euploid gametes by different meiotic systems in female and male germ lines and thus are be able to reproduce sexually in contrast to many other triploid organisms.


Germ Line Cell Female Germ Line Unpaired Chromosome Meiotic Chromosome Behavior Male Germ Line Cell 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank Dr. Marina Dan, Dr. Motonori Hoshi, and Dr. Gary Wessel for critically reading the manuscript. This work was supported by Grant-in-Aid for Challenging Exploratory Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan to M.M. (No. 23657008) and Grant-in-Aid for JSPS Fellows to A.C. (No. 25-5247) from Japan Society for the Promotion of Science.

Supplementary material

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Department of Biosciences and InformaticsKeio UniversityYokohamaJapan

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