@article {1766, title = {Triploid planarian reproduces truly bisexually with euploid gametes produced through a different meiotic system between sex.}, journal = {Chromosoma}, volume = {123}, year = {2014}, month = {2014 Jun}, pages = {265-72}, abstract = {

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.

}, keywords = {Animals, Chromosomes, Female, Germ Cells, Male, Meiosis, planarians, reproduction, Triploidy}, issn = {1432-0886}, doi = {10.1007/s00412-013-0449-2}, author = {Chinone, Ayako and Nodono, Hanae and Matsumoto, Midori} } @article {1731, title = {The identification of ᴅ-tryptophan as a bioactive substance for postembryonic ovarian development in the planarian Dugesia ryukyuensis}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {2017/03/24/online}, pages = {45175 - }, publisher = {The Author(s)}, url = {http://dx.doi.org/10.1038/srep45175}, author = {Kobayashi, Kazuya and Maezawa, Takanobu and Tanaka, Hiroyuki and Onuki, Hiroyuki and Horiguchi, Yurie and Hirota, Hiroshi and Ishida, Tetsuo and Horiike, Kihachiro and Agata, Yasutoshi and Aoki, Manabu and Hoshi, Motonori and Matsumoto, Midori} } @article {668, title = {Studies on the morphology, karyology and taxonomy of the japanese freshwater planarian Dugesia japonica Ichikawa et Kawakatsu, with a description of a new subspecies Dugesia japonica ryukyuensis subspec. nov.}, journal = {The Bulletin of Fuji Women{\textquoteright}s College}, volume = {14}, year = {1976}, pages = {81-126}, author = {Masaharu Kawakatsu and Oki, Iwashiro and Tamura, Sachiko and Hisao Sugino} } @article {springerlink:10.1007/BF00036366, title = {A review of chromosomal variation in Dugesia japonica and D. ryukyuensis in the Far East}, journal = {Hydrobiologia}, volume = {305}, year = {1995}, note = {10.1007/BF00036366}, pages = {79-84}, publisher = {Springer Netherlands}, abstract = {{The chromosome numbers of Dugesia japonica Ichikawa et Kawakatsu, 1964, are n = 8}}, issn = {0018-8158}, url = {http://dx.doi.org/10.1007/BF00036366}, author = {Tamura, Sachiko and Oki, Iwashiro and Masaharu Kawakatsu} } @article {springerlink:10.1007/BF00036363, title = {Taxonomy and geographical distribution of Dugesia japonica and D. ryukyuensis in the Far East}, journal = {Hydrobiologia}, volume = {305}, year = {1995}, note = {10.1007/BF00036363}, pages = {55-61}, publisher = {Springer Netherlands}, abstract = {

{Dugesia japonica Ichikawa et Kawakatsu, 1964, is a common and polymorphic species of freshwater planarian distributed widely in the Far East. In 1976 the geographic populations were separated into 2 subspecies (D.j.japonica and D.j. ryukyuensis). The taxonomy of this species is reconsidered once again from the morphological, anatomical, histological, and karyological viewpoints. From the result of these studies, D.j. ryukyuensis is elevated to the rank of species: D. ryukyuensis Kawakatsu, 1976. D. japonica (n = 8}

}, issn = {0018-8158}, url = {http://dx.doi.org/10.1007/BF00036363}, author = {Masaharu Kawakatsu and Oki, Iwashiro and Tamura, Sachiko} } @article {14, title = {The genus Dugesia in Australia, with its phylogenetic analysis and historical biogeography (Platyhelminthes, Tricladida, Dugesiidae)}, journal = {Zoologica Scripta}, volume = {27}, year = {1998}, pages = {273-289}, chapter = {273}, abstract = {

The new species Dugesia notogaea Sluys \& Kawakatsu, sp. n. is described from Queensland, Australia, representing the first record of the genus Dugesia for that continent. A phylogenetic analysis of the 68 species of Dugesia resulted in the discovery of a new apomorphy for the genus, and a cladogram showing two major phyletic groups. The distributional range of one group has a western accent, whereas that of the other group has an eastern emphasis; the ranges of these two groups overlap in Africa and the Mediterranean region. We attempt to determine the ancestral area for both the Dugesiidae and Dugesia. A scenario for the historical biogeography of the genus Dugesia is discussed. In this scenario it is presumed that the geological history of the Australasian region enabled Dugesia\’s from southeast Asia to colonize northern Australia.

}, doi = {10.1111/j.1463-6409.1998.tb00461.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1463-6409.1998.tb00461.x/abstract}, author = {Ronald Sluys and Masaharu Kawakatsu and Leigh Winsor} } @article {669, title = {The Dugesia ryukyuensis database as a molecular resource for studying switching of the reproductive system}, journal = {Zoological Science}, volume = {24}, number = {1}, year = {2007}, month = {01/2007}, pages = {31-37}, publisher = {Zoological Society of Japan}, abstract = {

The planarian Dugesia ryukyuensis reproduces both asexually and sexually, and can switch from one mode of reproduction to the other. We recently developed a method for experimentally switching reproduction of the planarian from the asexual to the sexual mode. We constructed a cDNA library from sexualized D. ryukyuensis and sequenced and analyzed 8,988 expressed sequence tags (ESTs). The ESTs were analyzed and grouped into 3,077 non-redundant sequences, leaving 1,929 singletons that formed the basis of unigene sets. Fifty-six percent of the cDNAs analyzed shared similarity (E-value\<1E -20) with sequences deposited in NCBI. Highly redundant sequences encoded granulin and actin, which are expressed in the whole body, and other redundant sequences encoded a Vasa-like protein, which is known to be a component of germ-line cells and is expressed in the ovary, and Y-protein, which is expressed in the testis. The sexualized planarian expressed sequence tag database (http://planaria.bio.keio.ac.jp/planaria/) is an open-access, online resource providing access to sequence, classification, clustering, and annotation data. This database should constitute a powerful tool for analyzing sexualization in planarians.

}, doi = {http://dx.doi.org/10.2108/zsj.24.31}, url = {http://www.bioone.org/doi/abs/10.2108/zsj.24.31}, author = {Hideyuki Ishizuka and Takanobu Maezawa and Junpei Kawauchi and Hanae Nodono and Yukako Hirao and Osamu Nishimura and Haruka Nakagawa and Kiyono Sekii and Kenta Tasaka and Hiroshi Tarui and Kiyokazu Agata and Hoshi, Motonori and Kobayashi, Kazuya and Yasubumi Sakakibara and Matsumoto, Midori} } @article {springerlink:10.1007/s00412-008-0148-6, title = {Production of diploid and triploid offspring by inbreeding of the triploid planarian Dugesia ryukyuensis}, journal = {Chromosoma}, volume = {117}, year = {2008}, note = {10.1007/s00412-008-0148-6}, pages = {289-296}, publisher = {Springer Berlin / Heidelberg}, abstract = {

Triploidy has generally been considered to be an evolutionary dead end due to problems of chromosomal pairing and segregation during meiosis. Thus, the formation of tetraploids and diploids from triploid types is a rare phenomenon. In the present study, we demonstrated that inbreeding of the triploid planarian Dugesia ryukyuensis resulted in both diploid and triploid offspring in nature. In the triploids of D. ryukyuensis , chiasmata between homologous chromosomes were observed in both female and male germ lines. This result suggests that both diploid and triploid offspring of this species are produced bisexually by zygotic fusion between sperm and eggs. Hence, this phenomenon may be a novel mechanism in planarian for escaping the triploid state.

}, issn = {0009-5915}, url = {http://dx.doi.org/10.1007/s00412-008-0148-6}, author = {Kobayashi, Kazuya and Ishizu, Hirotsugu and Arioka, Sachiko and Padilla Cabrera, Jocelyn and Hoshi, Motonori and Matsumoto, Midori} } @article {529, title = {Sex-inducing effect of a hydrophilic fraction on reproductive switching in the planarian Dugesia ryukyuensis (Seriata, Tricladida)}, journal = {Frontiers in Zoology}, volume = {8}, year = {2011}, pages = {23}, abstract = {

Background The mechanisms underlying the switching from an asexual to a sexual mode of reproduction, and vice versa, remain unknown in metazoans. In planarians, asexual worms acquire cryptic sexuality when fed with sexual worms, indicating that sexual worms contain a sex-inducing substance. Although such a chemical compound will provide clues about the mechanisms underlying the switching, information on the sex-inducing substance is poor. In order to identify this substance, we have established an assay system for sexual induction in asexual worms of Dugesia ryukyuensis by feeding them with sexual worms. Here, we carried out an isolation study on the sex-inducing substance using this assay system. Results After centrifugation of sexual worms homogenised in saline solution, we found that not only did the precipitate have a sex-inducing effect on the asexual worms, which has been shown previously, but the cytosolic fraction did as well. We confirmed that the sex-inducing activity in the cytosolic fraction was recovered in a hydrophilic fraction separated on an octadecylsilane (ODS) column. We showed that the sex-inducing substance in the hydrophilic fraction is papain-resistant and a putative low-molecular-weight compound of less than 500. We also suggest the presence of an enhancer of sexual induction with a molecular weight (MW) of more than 5 K in the hydrophilic fraction. Conclusion Our experiments showed the existence of a sex-inducing substance and an enhancer of sex-induction in a hydrophilic fraction, and a putative hydrophobic sex-inducing substance in the precipitate. Sexual induction in the asexual worms might be triggered by additive or synergistic effects of these chemical compounds.

}, doi = {10.1186/1742-9994-8-23}, url = {http://www.frontiersinzoology.com/content/pdf/1742-9994-8-23.pdf}, author = {Kobayashi, Kazuya and Hoshi, Motonori} } @article {482, title = {The Complete Mitochondrial Genome of Dugesia japonica (Platyhelminthes; Order Tricladida)}, journal = {Zoological Science}, volume = {29}, number = {10}, year = {2012}, month = {10/2012}, pages = {672-680}, publisher = {Zoological Society of Japan}, chapter = {672}, abstract = {

We used two sequencing methods, namely long polymerase chain reaction (PCR) and primer walking, to determine the complete mitochondrial DNA (mtDNA) sequence of Dugesia japonica and most of the mtDNA sequence of Dugesia ryukyuensis. The genome of D. japonica contained 36 genes including 12 of the 13 protein-coding genes characteristic of metazoan mitochondrial genomes, two ribosomal RNA genes, and 22 transfer RNA genes. The genome of D. ryukyuensis contained 33 genes, including 12 protein-coding genes, two ribosomal RNA genes, and 19 transfer RNA genes. The gene order of the mitochondrial genome from the Dugesia species showed no clear homology with either the Neodermata or other free-living Rhabditophora. This indicates that the platyhelminths exhibit great variability in mitochondrial gene order. This is the first complete sequence analysis of the mitochondrial genome of a free-living member of Rhabditophora, which will facilitate further studies on the population genetics and genomic evolution of the Platyhelminthes.

}, doi = {http://dx.doi.org/10.2108/zsj.29.672}, url = {http://www.bioone.org/doi/full/10.2108/zsj.29.672}, author = {Masato Sakai and Mitsuru Sakaizumi} } @article {729, title = {DrRad51 is required for chiasmata formation in meiosis in planarian Dugesia ryukyuensis}, journal = {Molecular Reproduction and Development}, year = {2014}, abstract = {

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.

}, doi = {10.1002/mrd.22308}, author = {Ayako Chinone and Matsumoto, Midori} } @article {727, title = {Planarian D-amino acid oxidase is involved in ovarian development during sexual induction}, journal = {Mechanisms of Development}, year = {2014}, url = {http://www.sciencedirect.com/science/article/pii/S0925477314000033}, author = {Takanobu Maezawa and Hiroyuki Tanaka and Haruka Nakagawa and Mizuki Ono and Manabu Aoki and Matsumoto, Midori and Tetsuo Ishida and Kihachiro Horiike and Kobayashi, Kazuya} }