02432nas a2200277 4500008004100000022001400041245012900055210006900184260001300253300001100266490000800277520163700285653001201922653001601934653001101950653001501961653000901976653001201985653001501997653001702012653001402029100001902043700001802062700002202080856005202102 2014 eng d a1432-088600aTriploid planarian reproduces truly bisexually with euploid gametes produced through a different meiotic system between sex.0 aTriploid planarian reproduces truly bisexually with euploid game c2014 Jun a265-720 v1233 a

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.

10aAnimals10aChromosomes10aFemale10aGerm Cells10aMale10aMeiosis10aplanarians10areproduction10aTriploidy1 aChinone, Ayako1 aNodono, Hanae1 aMatsumoto, Midori uhttps://continenticola.myspecies.info/node/176601724nas a2200109 4500008004100000245009900041210006900140520131200209100001901521700002201540856005201562 2014 eng d00aDrRad51 is required for chiasmata formation in meiosis in planarian Dugesia ryukyuensis0 aDrRad51 is required for chiasmata formation in meiosis in planar3 a

Rad51, a conserved eukaryotic protein, mediates the homologous-recombination repair of DNA double-strand breaks that occur during both mitosis and meiosis. During prophase I of meiosis, homologous recombination enhances the linkage between homologous chromosomes to increase the accuracy of segregation at anaphase I. In polyploidy situtations, however, difficulties with homologous chromosome segregation often disrupt meiosis. Yet, triploid individuals of the planarian Dugesia ryukyuensis are able to produce functional gametes through a specialized form of meiosis. To shed light on the molecular mechanisms that promote successful meiosis in triploid D. ryukyuensis, we investigated rad51 gene function. We isolated three genes of the Rad51 family, the Rad51 homolog Dr-rad51 and the Rad51 paralogs Dr-rad51B and Dr-rad51C. Dr-rad51 was expressed in germ-line and presumably in somatic stem cells, but was not necessary for the regeneration of somatic tissue. RNA-interference (RNAi) depletion of Dr-rad51 during sexualization did not affect chromosome behavior in zygotene oocytes, but did result in the loss of chiasmata at the diplotene stage. Thus, homologous recombination does not appear to be necessary for synapsis, but is needed for crossover and proper segregation in D. ryukyuensis.

1 aChinone, Ayako1 aMatsumoto, Midori uhttps://continenticola.myspecies.info/node/117300491nas a2200133 4500008004100000245010700041210006900148300001000217490000800227100003200235700001800267700002000285856005200305 2014 eng d00aA new and aberrant species of Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from Madagascar0 anew and aberrant species of iDugesiai Platyhelminthes Tricladida a71-880 v4251 aStocchino, Giacinta, Angela1 aSluys, Ronald1 aManconi, Renata uhttps://continenticola.myspecies.info/node/117700640nas a2200181 4500008004100000245009400041210006900135100002200204700002100226700002100247700001600268700001700284700002200301700001900323700002300342700002200365856007100387 2014 eng d00aPlanarian D-amino acid oxidase is involved in ovarian development during sexual induction0 aPlanarian Damino acid oxidase is involved in ovarian development1 aMaezawa, Takanobu1 aTanaka, Hiroyuki1 aNakagawa, Haruka1 aOno, Mizuki1 aAoki, Manabu1 aMatsumoto, Midori1 aIshida, Tetsuo1 aHoriike, Kihachiro1 aKobayashi, Kazuya uhttp://www.sciencedirect.com/science/article/pii/S0925477314000033