Karyological and taxonomic studies of Dugesia japonica Ichikawa et Kawakatsu in the Far East

Oki, Iwashiro; Tamura, Shinji; Yamayoshi, Takao; Kawakatsu, Masaharu

doi:10.1007/bf00026163

Cited by 30 publications

(20 citation statements)

References 6 publications

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“…In addition, as each species inhabits, and thus has adapted to, a specific natural niche, native planarian species may have additional advantages over invasive species during direct competition in their niche, which were not represented in these experiments. However, reports on the danger of invasive G-and J-planarians on natural planarian populations in the wild [3,7,10,19,23] suggest that our studies of species competition under ideal lab conditions may still provide new insight into the mechanisms by which invasive species outcompete native planarians in their natural habitat.…”

Section: Interacting Worms: Species Growth Rates and Competitionmentioning

confidence: 99%

“…Here we compare the reproductive strategies of three freshwater planarian species found in Southern Europe [3,4,10], North America [4,9], and East Asia [19,23], respectively: Schmidtea mediterranea (S), Dugesia tigrina (G), and Dugesia japonica (J). All three species are used as model organisms in the fields of regenerative medicine and stem cell biology [1,22].…”

Section: Introductionmentioning

confidence: 99%

“…It is therefore not obvious whether all three species would share the same strategy or whether they had evolved different solutions to the same problem based on the ecological differences of their natural habitats. Moreover, G-and J-planarians have been reported as invasive species [3,7,10,19,23]. In fact, D. tigrina can now frequently be found in Europe, often co-habiting with other planarian species [14] and D. japonica can be found across Japan and China [23].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, G-and J-planarians have been reported as invasive species [3,7,10,19,23]. In fact, D. tigrina can now frequently be found in Europe, often co-habiting with other planarian species [14] and D. japonica can be found across Japan and China [23].…”

Section: Introductionmentioning

confidence: 99%

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et al. 2015

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Planarians are among the most complex animals with the ability to regenerate complete organisms from small tissue pieces. This ability allows them to reproduce by splitting themselves into a head and a tail piece, making them a rare example of asexual reproduction via transverse fission in multi-cellular organisms. Due to the stochastic nature of long reproductive cycles, which range from days to months, few and primarily qualitative studies have been conducted to understand the reproductive behaviors of asexual planarians. We have executed the largest long-term study on planarian asexual reproduction to date, tracking more than 23,000 reproductive events of three common planarian species found in Europe, North America, and Asia, respectively: Schmidtea mediterranea, Dugesia tigrina, and Dugesia japonica. This unique data collection allowed us to perform a detailed statistical analysis of their reproductive strategies. Since the three species share a similar anatomy and mode of reproduction by transverse division, we were surprised to find that each species had acquired its own distinct strategy for optimizing its reproductive success. We statistically examined each strategy, associated trade-offs, and the potential regulatory mechanisms on the population level. Interestingly, models for cell cycle length regulation in unicellular organisms could be directly applied to describe reproductive cycle lengths of planarians, despite the difference in underlying biological mechanisms. Finally, we exam-Electronic supplementary material The online version of this article (ined the ecological implications of each strategy through intra-and inter-species competition experiments and found that D. japonica outcompeted the other two species due to its relatively equal distribution of resources on head and tail pieces, its cannibalistic behaviors and ability to thrive in crowded environments. These results show that this species would pose a serious threat to endogenous planarian populations if accidentally introduced in their habitats.

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Section: Interacting Worms: Species Growth Rates and Competitionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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et al. 2015

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“…Mitotic stability and relative ubiquity of extra-A chromosomes in polyploids suggests that it is neither a simple aneuploid phenomenon, nor an artefact induced by colchicine treatment (Ribas et al, 1988). Such aneuploidy has been observed in many planarian species (Benazzi & Benazzi Lentati, 1976;Benazzi Lentati, 1970; Canovai, 1989;Dahm, 1958;De Vries et al, 1984;Le Moigne, 1962;Lepori, 1950;Lepori 1954b;Lepori and Pala, 1982;Melander, 1963;Oki et al, 1981) including P. nigra (Lepori, 1950). Extra-A elements could either be polysomics, or another type of B chromosome that morphologically resembles the standard (A) chromosomes, and we are presently investigating these alternative hypotheses using chromosome banding techniques (Sharbel et al, 1998).…”

Section: Distribution and Frequencies Of Supernumerary Chromosomesmentioning

confidence: 90%

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1998

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Stem cells from innate sexual but not acquired sexual planarians have the capability to form a sexual individual

Nodono

Ishino

Hoshi

et al. 2012

Molecular Reproduction Devel

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Planarian species may harbor as many as three populations with different reproductive strategies. Animals from innate asexual (AS) and innate sexual (InS) populations reproduce only by fission and cross-fertilization, respectively, whereas the third population switches seasonally between the two reproductive modes. AS worms can be experimentally sexualized by feeding them with minced InS worms; we termed the resulting animals "acquired sexual" (AqS) worms. Both AqS and InS worms exhibit sexualizing activity when used as feed, suggesting that they maintain their sexual state via endogenous sexualizing substances, although the mechanisms underlying determination of reproductive strategy and sexual switching in these metazoans remain enigmatic. Therefore, we compared the endogenous sexualizing activity of InS worms and AqS worms. First, we amputated mature worms and assessed if they could re-enter a sexual state. Regenerants of InS worms, but not AqS worms, were only sexual, indicating that sexual state regulation comprises two steps: (1) autonomous initiation of sexualizing substance production and (2) maintenance of the sexual state by continuous production of sexualizing substances. Next, InS neoblasts were characterized by transplantation, finding that they successfully engrafted, proliferated, and replaced all recipient cells. Under such conditions, the AS recipients of InS worm neoblasts, but not those of AqS worms, became sexual. These results clearly show that there is a neoblast-autonomous determination of reproductive strategy in planarians.

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Karyological and taxonomic studies of Dugesia japonica Ichikawa et Kawakatsu in the Far East

Cited by 30 publications

References 6 publications

To Each His Own

To Each His Own

Untitled

Stem cells from innate sexual but not acquired sexual planarians have the capability to form a sexual individual

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