Overview of life cycles in model species of the genus<i>Dugesia</i>(Platyhelminthes: Tricladida)

Stocchino, Giacinta Angela; Manconi, Renata

doi:10.1080/11250003.2013.822025

Cited by 21 publications

(15 citation statements)

References 26 publications

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“…In contrast, exfissiparous individuals of D. benazzii Lepori, 1951 andD. etrusca Benazzi, 1946 do not develop hyperplasic ovaries (Stocchino & Manconi, 2013).…”

Section: 1mentioning

confidence: 91%

The invasive alien freshwater flatworm Girardia tigrina (Girard, 1850) (Platyhelminthes, Tricladida) in Western Europe: new insights into its morphology, karyology and reproductive biology

Stocchino

Sluys

Harrath

et al. 2019

Contributions to Zoology

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Invasions of alien species form one of the major threats to global biodiversity. Among planarian flatworms many species are known to be invasive, in several cases strongly affecting local ecosystems. Therefore, a detailed knowledge on the biology of an invasive species is of utmost importance for understanding the process of invasion, the cause of its success, and the subsequent ecological impact on native species. This paper provides new information on the biology of introduced populations of the freshwater flatworm Girardia tigrina (Girard, 1850) from Europe. This species is a native of the Nearctic Region that was accidentally introduced into Europe in the 1920s. Since then, numerous records across the European continent bear witness of the invasiveness of this species, although only a few studies focused on the biology of the introduced populations. We report on the morphology of sexualized individuals from a fissiparous Italian population, representing the second record of spontaneous sexualization of fissiparous individuals in this species. A detailed morphological account of the reproductive apparatus of these ex-fissiparous animals is presented. Our results increased the number of morphological groups previously recognized for European populations of G. tigrina, thus corroborating the hypothesis on multiple independent introductions to this continent. Karyological results obtained from our fissiparous Italian individuals revealed a constant diploid chromosome complement of sixteen chromosomes. Further, we document the marked intraspecific variation in several morphological features of this species.

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“…In contrast, exfissiparous individuals of D. benazzii Lepori, 1951 andD. etrusca Benazzi, 1946 do not develop hyperplasic ovaries (Stocchino & Manconi, 2013).…”

Section: 1mentioning

confidence: 91%

The invasive alien freshwater flatworm Girardia tigrina (Girard, 1850) (Platyhelminthes, Tricladida) in Western Europe: new insights into its morphology, karyology and reproductive biology

Stocchino

Sluys

Harrath

et al. 2019

Contributions to Zoology

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“…Facultative reproduction in the genus Schmidtea involves the alternation of parthenogenesis and sexual reproduction [32], while facultative individuals of Dugesia alternate fissiparity with sex ([33], and references therein). It could be thought that triploid facultative Dugesia individuals may in fact alternate fission with parthenogenesis, due to the disadvantages of polyploids during meiotic processes [34].…”

Section: Introductionmentioning

confidence: 99%

Outstanding intraindividual genetic diversity in fissiparous planarians (Dugesia, Platyhelminthes) with facultative sex

et al. 2019

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Background Predicted genetic consequences of asexuality include high intraindividual genetic diversity (i.e., the Meselson effect) and accumulation of deleterious mutations (i.e., Muller’s Ratchet), among others. These consequences have been largely studied in parthenogenetic organisms, but studies on fissiparous species are scarce. Differing from parthenogens, fissiparous organisms inherit part of the soma of the progenitor, including somatic mutations. Thus, in the long term, fissiparous reproduction may also result in genetic mosaicism, besides the presence of the Meselson effect and Muller’s Ratchet. Dugesiidae planarians show outstanding regeneration capabilities, allowing them to naturally reproduce by fission, either strictly or combined with sex (facultative). Therefore, they are an ideal model to analyze the genetic footprint of fissiparous reproduction, both when it is alternated with sex and when it is the only mode of reproduction. Results In the present study, we generate and analyze intraindividual cloned data of a nuclear and a mitochondrial gene of sexual, fissiparous and facultative wild populations of the species Dugesia subtentaculata . We find that most individuals, independently of their reproductive strategy, are mosaics. However, the intraindividual haplotype and nucleotide diversity of fissiparous and facultative individuals is significantly higher than in sexual individuals, with no signs of Muller’s Ratchet. Finally, we also find that this high intraindividual genetic diversity of fissiparous and facultative individuals is composed by different combinations of ancestral and derived haplotypes of the species. Conclusions The intraindividual analyses of genetic diversity point out that fissiparous reproduction leaves a very special genetic footprint in individuals, characterized by mosaicism combined with the Meselson effect (named in the present study as the mosaic Meselson effect ). Interestingly, the different intraindividual combinations of ancestral and derivate genetic diversity indicate that haplotypes generated during periods of fissiparous reproduction can be also transmitted to the progeny through sexual events, resulting in offspring showing a wide range of genetic diversity and putatively allowing purifying selection to act at both intraindividual and individual level. Further investigations, using Dugesia planarians as model organisms, would be of great value to delve into this new model of genetic evolution by the combination of fission and sex. Electronic supplementary material The online version of this article (10.1186/s12862-019-1440-1) contains supplementary material, which is available to authorized users.

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“…Under certain conditions (mostly in the laboratory) triploid fissiparous planarians can develop hyperplasic ovaries and a copulatory apparatus [ 4 , 9 , 10 ], these individuals are known as ex-fissiparous. In D. sicula , it has been observed that some ex-fissiparous individuals laid cocoons but remained sterile [ 4 , 9 - 11 ], which indicated that asexual populations have lost the capability to sexually reproduce.…”

Section: Introductionmentioning

confidence: 99%

Dugesia sicula (Platyhelminthes, Tricladida): the colonizing success of an asexual Planarian

Lázaro

Riutort

2013

BMC Evol Biol

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BackgroundDugesia sicula is the only species of its genus not presenting an endemic or restricted distribution within the Mediterranean area. It mostly comprises fissiparous populations (asexual reproduction by body division and regeneration), most likely sexually sterile, and characterized by an extremely low genetic diversity interpreted as the consequence of a recent anthropic expansion. However, its fissiparous reproduction can result in an apparent lack of diversity within the species, since genetic variation within individuals can be as large as between them because most individuals within a population are clones. We have estimated haplotype and nucleotide diversity of cytochrome oxidase I within and among individuals along the species distribution of a broad sample of D. sicula, including asexual and the two only sexual populations known today; and predicted its potential distribution based on climatic variables. Our aim was to determine the centre of colonisation origin, whether the populations are recent, and whether the species is expanding.ResultsThe species presents 3 most frequent haplotypes, differing in a maximum of 11 base pairs. As expected from their fissiparous mode of reproduction, in half of all the analysed localities many individuals have multiple heteroplasmic haplotypes. The distribution of haplotypes is not geographically structured; however, the distribution of haplotypes and heteroplasmic populations shows higher diversity in the central Mediterranean region. The potential distribution predicted by climatic variables based modelling shows a preference for coastal areas and fits well with the observed data.ConclusionsThe distribution and frequency of the most frequent haplotypes and the presence of heteroplasmic individuals allow us to gain an understanding of the recent history of the species, together with previous knowledge on its phylogenetic relationships and age: The species most probably originated in Africa and dispersed through the central Mediterranean. After one or multiple populations became triploid and fissiparous, the species colonized the Mediterranean basin, likely both by its own means and helped by human activities. Its present distribution practically fulfils its potential distribution as modelled with climatic variables. Its prevalence in coastal regions with higher water temperatures predicts a likely future expansion to northern and more interior areas following the increase in temperatures due to climate change.

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

Cited by 21 publications

References 26 publications

The invasive alien freshwater flatworm Girardia tigrina (Girard, 1850) (Platyhelminthes, Tricladida) in Western Europe: new insights into its morphology, karyology and reproductive biology

The invasive alien freshwater flatworm Girardia tigrina (Girard, 1850) (Platyhelminthes, Tricladida) in Western Europe: new insights into its morphology, karyology and reproductive biology

Outstanding intraindividual genetic diversity in fissiparous planarians (Dugesia, Platyhelminthes) with facultative sex

Dugesia sicula (Platyhelminthes, Tricladida): the colonizing success of an asexual Planarian

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