Production of diploid and triploid offspring by inbreeding of the triploid planarian Dugesia ryukyuensis

Kobayashi, Kazuya; Ishizu, Hideki; Arioka, Sachiko; Cabrera, Jocelyn Padilla; Hoshi, Motonori; Matsumoto, Midori

doi:10.1007/s00412-008-0148-6

Cited by 9 publications

(14 citation statements)

References 33 publications

(29 reference statements)

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“…Stocchino et al 2012). Sexualised specimens of D. ryukyuensis differ from our fertile ex-fissiparous lineages also in that offspring in populations of the former species consisted of both fissiparous and sexual individuals (Kobayashi et al 2009(Kobayashi et al , 2012. The coexistence of sexual and asexual individuals in mixed populations rules out the occurrence of alternating stages of sexual and fissiparous reproduction in the same individual.…”

Section: Discussionmentioning

confidence: 99%

Overview of life cycles in model species of the genusDugesia(Platyhelminthes: Tricladida)

Stocchino

Manconi

2013

Italian Journal of Zoology

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An overview of the reproductive patterns of seven model species of triclads belonging to the genus Dugesia from circum-Mediterranean and Afrotropical freshwater is provided. Populations can reproduce exclusively sexually or exclusively asexually by fissiparity but the coexistence of both reproductive modes is displayed by some lineages. The comparison of data on the life cycles as documented in the literature with new data highlights a wide array of potentialities to shift from an asexual to a sexual state and vice versa in species with fissiparous populations. Life cycles are poorly diversified in species reproducing only sexually. Among fissiparous populations, planarians may sexualise, displaying various grades of reproductive functionality under laboratory conditions. Unexpectedly, asexual reproduction by fission occurred spontaneously in two species during the sexual state of ex-fissiparous individuals. The capacity to develop or reduce the reproductive apparatus during the life cycle either in sexual or in ex-fissiparous individuals illustrates the considerable morphogenetic plasticity in planarians. The Dugesia case contributes to the modelling of reproductive patterns and strategies in basal Metazoa as a continuum from sexual to asexual reproduction and vice versa, rather than a simple clear-cut alternative.

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Section: Discussionmentioning

confidence: 99%

Overview of life cycles in model species of the genusDugesia(Platyhelminthes: Tricladida)

Stocchino

Manconi

2013

Italian Journal of Zoology

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“…AqS worms, which are transformed from asexual to sexual worms, produce offspring that reproduce either asexually or sexually. In addition, AqS worms can reproduce by genetic cross-mixing (Kobayashi et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…To prepare metaphase spreads of mitotic chromosomes for imaging, a previously published hybridization protocol was followed (Kobayashi et al, 2008). The preparations were dried overnight and stored at -80°C.…”

Section: Chromosome Preparation and Fluorescence In Situ Hybridizationmentioning

confidence: 99%

Innate sexuality determines the mechanisms of telomere maintenance

Tasaka

Yokoyama²,

Nodono³

et al. 2013

Int. J. Dev. Biol.

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Recently, telomere length has been shown to be differentially regulated in asexually and sexually reproducing planarians. In addition, it was found that asexual worms maintain telomere length somatically during reproduction by fission or when regeneration is induced by amputation, whereas sexual worms only achieve telomere elongation through sexual reproduction. We have established an experimental bioassay system to induce switching from asexual to sexual reproduction in planarians, that is, sexualization. In this study, the relationship between the reproductive mode and telomere maintenance was investigated using innate asexually reproducing worms, innate sexually reproducing worms, and experimentally sexualized worms. Here, we show that innate asexual planarians maintain telomere length during cell division and that innate sexual planarians exhibit telomere shortening. However, experimental sexualized worms maintain telomere length during cell division. These results indicate that innate sexuality is linked to the mechanism of telomere maintenance. KEY WORDS: telomere length, innate sexuality, planarianProkaryotes maintain an intact genome by asexual reproduction and therefore do not have a fixed lifespan. However, eukaryotic organisms that reproduce sexually produce offspring that have completely new genomes due to recombination of the parental genomes. In these organisms, cell lineages have a defined lifespan, as do the organisms themselves (Hug 2006;Williams 1957), which is linked to telomere shortening during each round of eukaryotic DNA replication. However, some eukaryotic animals can also reproduce asexually; therefore, asexual species, such as planarians, may not have a fixed lifespan.The planarian is a useful model animal for investigating the relationship between the reproductive mode and predetermined lifespan. Many planarian species have strains with different modes of reproduction: exclusively asexual, exclusively sexual, or switching between them seasonally (Hyman, 1951). Although sexual planarians do not reproduce asexually (i.e., spontaneous fission), they can regenerate all tissues after amputation, including germ cells and somatic cells of the genital organs . The mechanism controlling lifespan in these species has not been elucidated, but many extrinsic factors, including oxidative stress and regulation of energy production, and intrinsic factors, such as maintenance of telomere length, are expected to be involved. It was recently shown in the planarian Schmidtea Int.

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“…We have previously demonstrated that diploid and triploid offspring are produced in a ratio of 1:2 or 1:3 with a significance level of 5% (see table 1 in Kobayashi et al 2008). In the present study, to examine the relationship between polyploidy and the mode of reproduction in the offspring, karyological investigations were conducted on asexual and sexual offspring derived from the same cocoons (Table 3).…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, we have demonstrated that inbreeding of the acquired sexuals results in both diploid and triploid offspring. Recent studies have indicated that meiosis occurs in both female and male germ lines in acquired sexuals, which undergo sexual reproduction (Kobayashi et al 2008). The mechanisms that determine the reproductive mode in planarians are poorly understood (Grasso & Benazzi 1973;Benazzi 1974;Benazzi & Benazzi 1976;Baguñà et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Production of asexual and sexual offspring in the triploid sexual planarian Dugesia ryukyuensis

Kobayashi¹,

Arioka²,

Hoshi³

et al. 2009

Integrative Zoology

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Certain freshwater planarians reproduce asexually as well as sexually, and their chromosomal ploidies include polyploidy, aneuploidy and mixoploidy. Previously, we successfully performed an experiment in which a clonal population produced by asexual reproduction of the Dugesia ryukyuensis (OH strain) switched to the sexual mode of reproduction. Worms of this strain are triploid with a pericentric inversion on Chromosome 4. The worms were switched to sexual reproduction after being fed with sexually mature Bdellocephala brunnea, which is a sexually reproducing species. The resulting sexualized OH strain produced cocoons filled with several eggs. Two putative factors, Mendelian factor(s) and chromosomal control(s), have been proposed as determining the reproductive mode. The present study demonstrated that inbreeding of the resultant sexualized worms produced the following four types of offspring through sexual reproduction: diploid asexual worms, triploid asexual worms, diploid sexual worms and triploid sexual worms. The chromosomal mutation on Chromosome 4 was inherited by these offspring independent of their reproductive mode. These results provide two important pieces of information: (i) the putative genetic factor was not necessarily inherited in a Mendelian fashion; and (ii) the reproductive mode is not regulated by chromosomal changes such as polyploidy or chromosomal mutations. This suggests that asexuality in D. ryukyuensis is regulated by an unknown factor(s) other than a Mendelian factor or a chromosomal control.

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Production of diploid and triploid offspring by inbreeding of the triploid planarian Dugesia ryukyuensis

Cited by 9 publications

References 33 publications

Overview of life cycles in model species of the genusDugesia(Platyhelminthes: Tricladida)

Overview of life cycles in model species of the genusDugesia(Platyhelminthes: Tricladida)

Innate sexuality determines the mechanisms of telomere maintenance

Production of asexual and sexual offspring in the triploid sexual planarian Dugesia ryukyuensis

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