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  • 1.
    Curini-Galletti, Marco
    et al.
    Universita` di Sassari, Italy.
    Artois, Tom
    Hasselt University, Belgium.
    Delogu, Valentina
    Universita` di Sassari, Italy.
    De Smet, Willem H.
    University of Antwerp, Belgium.
    Fontaneto, Diego
    Swedish Museum of Natural History, Sweden; Imperial College London, United Kingdom.
    Jondelius, Ulf
    Swedish Museum of Natural History, Sweden.
    Leasi, Francesca
    Imperial College London, United Kingdom; Universtità di Modena e Reggio Emilia, Italy.
    Martínez, Alejandro
    University of Copenhagen, Denmark.
    Meyer-Wachsmuth, Inga
    Swedish Museum of Natural History, Sweden.
    Nilsson, Karin Sara
    Swedish Museum of Natural History, Sweden.
    Tongiorgi, Paolo
    Universtità di Modena e Reggio Emilia, Italy.
    Worsaae, Katrine
    University of Copenhagen, Denmark.
    Todaro, M. Antonio
    Universtità di Modena e Reggio Emilia, Italy.
    Patterns of Diversity in Soft-Bodied Meiofauna: Dispersal Ability and Body Size Matter2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 3, article id e33801Article in journal (Refereed)
    Abstract [en]

    Background: Biogeographical and macroecological principles are derived from patterns of distribution in large organisms, whereas microscopic ones have often been considered uninteresting, because of their supposed wide distribution. Here, after reporting the results of an intensive faunistic survey of marine microscopic animals (meiofauna) in Northern Sardinia, we test for the effect of body size, dispersal ability, and habitat features on the patterns of distribution of several groups.

    Methodology/Principal Findings: As a dataset we use the results of a workshop held at La Maddalena (Sardinia, Italy) in September 2010, aimed at studying selected taxa of soft-bodied meiofauna (Acoela, Annelida, Gastrotricha, Nemertodermatida, Platyhelminthes and Rotifera), in conjunction with data on the same taxa obtained during a previous workshop hosted at Tja ̈rno ̈ (Western Sweden) in September 2007. Using linear mixed effects models and model averaging while accounting for sampling bias and potential pseudoreplication, we found evidence that: (1) meiofaunal groups with more restricted distribution are the ones with low dispersal potential; (2) meiofaunal groups with higher probability of finding new species for science are the ones with low dispersal potential; (3) the proportion of the global species pool of each meiofaunal group present in each area at the regional scale is negatively related to body size, and positively related to their occurrence in the endobenthic habitat.

    Conclusion/Significance: Our macroecological analysis of meiofauna, in the framework of the ubiquity hypothesis for microscopic organisms, indicates that not only body size but mostly dispersal ability and also occurrence in the endobenthic habitat are important correlates of diversity for these understudied animals, with different importance at different spatial scales. Furthermore, since the Western Mediterranean is one of the best-studied areas in the world, the large number of undescribed species (37%) highlights that the census of marine meiofauna is still very far from being complete. 

  • 2.
    Kånneby, Tobias
    et al.
    The Swedish Museum of Natural History .
    Todaro, M. Antonio
    Jondelius, Ulf
    The Swedish Museum of Natural History.
    A Phylogenetic approach to species delimitation in freshwater Gastrotricha from Sweden2012In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 683, no 1, p. 185-202Article in journal (Refereed)
    Abstract [en]

    Gastrotricha is a cosmopolitan group of aquatic invertebrates. To date approximately 765 species have been described. This study is the first to deal with species delimitation and cryptic species of freshwater Gastrotricha. Three commonly encountered species, Heterolepidoderma ocellatum, Lepidochaetus zelinkai and Lepidodermella squamata, are investigated for cryptic speciation. Most of the material is based on Swedish specimens but closely related species from other parts of the world are also included. Taxonomic revisions are supported by phylogenies based on 18S rRNA, 28S rRNA and COI mtDNA of freshwater Chaetonotidae from several genera and inferred from Bayesian and maximum likelihood approaches. Heterolepidoderma ocellatum f. sphagnophilum is raised to species level, becoming H. acidophilum n. sp. Moreover, genetic data based on COI indicates high variation between two morphologically very similar groups of Lepidodermella squamata. The extent of cryptic speciation in L. zelinkai appears low. Based on the phylogenetic hypothesis presented in this paper the new species, Lepidodermella intermedia n. sp., from northernSweden is also described. The phylogenetic hypothesis generated show that Chaetonotidae is a non-monophyletic group.  

  • 3.
    Kånneby, Tobias
    et al.
    Naturhistoriska riksmuseet, Enheten för evertebratzoologi.
    Todaro, M. Antonio
    Jondelius, Ulf
    Naturhistoriska riksmuseet, enheten för evertebratzoologi.
    One new species and records of Ichthydium Ehrenberg, 1830 (Gastrotricha: Chaetonotida) from Sweden with a key to the genus2009In: Zootaxa, ISSN 1175-5326, E-ISSN 1175-5334, no 2278, p. 26-46Article in journal (Refereed)
    Abstract [en]

    The freshwater gastrotrich fauna of Sweden is poorly known. Only seven species of freshwater gastrotrichs have been reported so far. This paper is the first in a series of contributions about the Swedish freshwater gastrotrich fauna. Here we describe one new species, Ichthydium skandicum n. sp., from Jamtland, northern Sweden. The new species falls within the boundary of the subgenus Forficulichthys and is morphologically closest to Ichthydium tanytrichum from which it can be differentiated based on the presence of four pairs of dorsal, keeled scales in the posterior trunk region. Moreover, we provide morphometric data for three additional Ichthydium species: I. diacanthum, I. squamigerum and I. tanytrichum, Italian species all of which are reported for the first time outside Italy. Considering the accompanying fauna, a total of thirteen freshwater Gastrotricha are reported for the first time from Sweden. Finally we present a dichotomous key for Ichthydium along with distributional data of the species considered.

  • 4.
    Kånneby, Tobias
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology.
    Todaro, M. Antonio
    Jondelius, Ulf
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology.
    Phylogeny of Chaetonotidae (Gastrotricha) inferred from nuclear and mitochondrial genesManuscript (preprint) (Other academic)
    Abstract [en]

    Chaetonotidae is the largest family within Gastrotricha with almost 400 nominal species, represented in both freshwater and marine habitats. The group is probably non-monophyletic and suffers from a troubled taxonomy. Current classification is to a great extent based on shape and distribution of cuticular structures, characters that are highly variable. We present the most densely sampled molecular study so far where 17 out of 31 genera belonging to Chaetonotida are represented. Bayesian and maximum likelihood approaches based on 18S rDNA, 28S rDNA and COI mtDNA are used to reconstruct relationships within Chaetonotidae. The use of cuticular structures for supra-specific classification within the group is evaluated and the question of dispersal between marine and freshwater habitats is addressed. Moreover the subgeneric classification of Chaetonotus is tested in a phylogenetic context. Our results show high support for a clade containing Dasydytidae nested within Chaetonotidae. Within this clade only 3 genera are monophyletic following current classification. Genera containing both marine and freshwater species never form monophyletic clades and group with other species according to habitat. Marine members of Aspidiophorus appear to be the sister group of all other Chaetonotidae and Dasydytidae, indicating a marine origin of the clade. Halichaetonotus and marine Heterolepidoderma form a monophyletic group in a sister group relationship to freshwater species, pointing towards a secondary invasion to marine environments of these taxa. Our study shows the problems of current classification based on cuticular structures, characters that show homoplasy for deeper relationships.

  • 5.
    Meyer-Wachsmuth, Inga
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology. Swedish Museum of Natural History, Sweden.
    Curini Galletti, Marco
    Jondelius, Ulf
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology. Swedish Museum of Natural History, Sweden.
    Hyper-Cryptic Marine Meiofauna: Species Complexes in Nemertodermatida2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 9, article id e107688Article in journal (Refereed)
    Abstract [en]

    Nemertodermatida are microscopically small, benthic marine worms. Specimens of two nominal species, Sterreria psammicola and Nemertinoides elongatus from 33 locations worldwide were sequenced for three molecular markers. Species delimitation and validation was done using gene trees, haplotype networks and multilocus Bayesian analysis. We found 20 supported species of which nine: Nemertinoides glandulosum n.sp., N. wolfgangi n.sp., Sterreria boucheti n.sp., S. lundini n.sp., S. martindalei n.sp., S. monolithes n.sp., S. papuensis n.sp., S. variabilis n.sp. and S. ylvae n.sp., are described including nucleotide-based diagnoses. The distribution patterns indicate transoceanic dispersal in some of the species. Sympatric species were found in many cases. The high level of cryptic diversity in this meiofauna group implies that marine diversity may be higher than previously estimated. 

  • 6.
    Meyer-Wachsmuth, Inga
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology. Naturhistoriska riksmuseet, Enheten för zoologi; Swedish Museum of Natural History, Department of Zoology.
    Jondelius, Ulf
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology. Naturhistoriska riksmuseet, Enheten för zoologi; Swedish Museum of Natural History, Department of Zoology.
    A multigene molecular assessment reveals deep divergence in the phylogeny of NemertodermatidaManuscript (preprint) (Other academic)
    Abstract [en]

    Here we present a comprehensive phylogeny of Nemertodermatida, a taxon of microscopic marine worms, based for the first on molecular marker with consideration of morphological characters. Our dataset comprises three nuclear genes and most nominal and putative species including recently described cryptic species; only species of the genus Ascoparia could not be obtained. We show that the two families of Nemertodermatida, Ascopariidae and Nemertodermatidae, are retrieved as separate clusters, although not in all analyses as sister groups. We also validate sequences published before 2013 against our dataset; some sequences are shown to be chimeric and have falsified prior hypotheses about nemertodermatid phylogeny, other sequences should be assigned new names. We also show that the genus Nemertoderma needs revision. 

  • 7.
    Meyer-Wachsmuth, Inga
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden; Biology Centre of the Czech Academy of Sciences, Czech Republic.
    Jondelius, Ulf
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Interrelationships of Nemertodermatida2016In: Organisms Diversity & Evolution, ISSN 1439-6092, E-ISSN 1618-1077, Vol. 16, no 1, p. 73-84Article in journal (Refereed)
    Abstract [en]

    Nemertodermatida is a small taxon of microscopic marine worms, which were originally classified within Platyhelminthes. Today they are hypothesized to be either an early bilaterian lineage or the sister group to Ambulacraria within Deuterostomia. These two hypotheses indicate widely diverging evolutionary histories in this largely neglected group. Here, we analyse the phylogeny of Nemertodermatida using nucleotide sequences from the ribosomal LSU and SSU genes and the protein coding Histone 3 gene. All currently known species except Ascoparia neglecta and Ascoparia secunda were included in the study in addition to several yet undescribed species. Ascopariidae and Nemertodermatidae are retrieved as separate clades, although not in all analyses as sister groups. Non-monophyly of Nemertodermatida was rejected by the Approximately Unbiased test. Nemertodermatid nucleotide sequences deposited in Genbank before 2013 were validated against our dataset; some of them are shown to be chimeric implying falsification of prior hypotheses about nemertodermatid phylogeny: other sequences should be assigned new names. We also show that the genus Nemertoderma needs revision.

  • 8.
    Meyer-Wachsmuth, Inga
    et al.
    Department of Invertebrate Zoology, Swedish Museum of Natural History.
    Raikova, Olga I.
    Russian Academy of Sciences.
    Jondelius, Ulf
    Department of Invertebrate Zoology, Swedish Museum of Natural History.
    The muscular system of Nemertoderma westbladi and Meara stichopi (Nemertodermatida, Acoelomorpha)2013In: Zoomorphology, ISSN 0720-213X, E-ISSN 1432-234X, Vol. 132, no 3, p. 239-252Article in journal (Refereed)
    Abstract [en]

    Nemertodermatida is a small taxon of marine worm-like animals; its position in the tree of life is highly contested The musculature of Nemertoderma westbladi and Meara stichopi is studied here in detail using fluorescent phalloidin and confocal microscopy.

    In both species the musculature is composed of an outer layer of circular and an inner layer of longitudinal musculature, diagonal muscles form a distinct layer in N westbladi but in M. stichopi these fibres connect to both other layers. The supraterminally opening male pore and antrum are formed by invagination of the whole body-wall in both species and the seminal vesicle is lined by a thin net of musculature only in full male maturity. Modifications of the ventral body-wall adjacent to the mouth are small and transient in N. westbladi including no extra musculature whereas it consists of additional strong U-shaped musculature in M. stichopi. Myogenesis in N. westbladi is not finished in hatchlings and will be completed dorsally in juvenile specimens and ventrally in male mature ones, after the loss of the mouth.

    Musculature between the two species differs considerably and might give insights into the internal relationships of Nemertodermatida and might prove to be useful in studies investigating their phylogenetic position. More data of other species and developmental changes are needed.

  • 9. Raikova, Olga I.
    et al.
    Meyer-Wachsmuth, Inga
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden; Biology Centre of the Czech Academy of Sciences, Czech Republic.
    Jondelius, Ulf
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    The plastic nervous system of Nemertodermatida2016In: Organisms Diversity & Evolution, ISSN 1439-6092, E-ISSN 1618-1077, Vol. 16, no 1, p. 85-104Article in journal (Refereed)
    Abstract [en]

    Nemertodermatida are microscopic marine worms likely to be the sister group to acoels, forming with them the earliest extant branch of bilaterian animals, although their phylogenetic position is debated. The nervous system of Flagellophora cf. apelti, Sterreria spp. and Nemertoderma cf. westbladi has been investigated by immunohistochemistry and confocal microscopy using anti-tubulin, anti-5-HT and anti-FMRFamide antibodies. The nervous system of F. cf. apelti is composed of a large neuropile and a loose brain at the level of the statocysts with several nerve fibres surrounding them and innervating the broom organ. Sterreria spp. shows a commissural-like brain and several neurite bundles going frontad and caudad from this. At the level of the statocysts there is also a thicker aggregation of immunoreactive fibres. The nervous system of N. cf. westbladi consists of a nerve ring lying outside the body wall musculature at the level of the statocyst and a pair of ventro-lateral neurite bundles, from which extend thinner fibres innervating the ventral side of the animal. Numerous bottle-shaped glands were observed, innervated by fibres starting both from the brain and the neurite bundles. The nervous system of the nemertodermatids studied to date displays no common pattern; instead, there is considerable plasticity in the general morphology of the nervous system. In addition, the musculature of Sterreria spp. has been studied by phalloidin staining. It shows diagonal muscles in the anterior quarter of the body and a simple orthogonal grid in the posterior three quarters, being simpler than that of the other nemertodermatids. High-resolution differential interference contrast microscopy permitted to better visualize some morphological characters of the species studied, such as statocysts, sperm and glands and, in combination with anti-tubulin staining, describe in detail the broom organ in F. cf. apelti. Finally, we note an apparent absence of innervation of the gut in Nemertodermatida similar to the condition in Xenoturbella.

  • 10. Todaro, M. Antonio
    et al.
    Kånneby, Tobias
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology.
    Dal Zotto, Matteo
    Jondelius, Ulf
    Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology.
    Phylogeny of Thaumastodermatidae (Gastrotricha: Macrodasyida) Inferred from Nuclear and Mitochondrial Sequence Data2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 3, p. e17892-Article in journal (Refereed)
    Abstract [en]

    Background

    Phylogenetic relationships within Gastrotricha are poorly known. Attempts to shed light on this subject using morphological traits have led to hypotheses lacking satisfactory statistical support; it seemed therefore that a different approach was needed.

    Methodology/Principal Findings

    In this paper we attempt to elucidate the relationships within the taxonomically vast family Thaumastodermatidae (Macrodasyida) using molecular sequence data. The study includes representatives of all the extant genera of the family and for the first time uses a multi-gene approach to infer evolutionary liaisons within Gastrotricha. The final data set comprises sequences of three genes (18S, 28S rDNA and COI mtDNA) from 41 species, including 29 thaumastodermatids, 11 non-thaumastodermatid macrodasyidans and a single chaetonotidan. Molecular data was analyzed as a combined set of 3 genes and as individual genes, using Bayesian and maximum likelihood approaches. Two different outgroups were used: Xenotrichula intermedia (Chaetonotida) and members of the putative basal Dactylopodola (Macrodasyida). Thaumastodermatidae and all other sampled macrodasyidan families were found monophyletic except for Cephalodasyidae. Within Thaumastodermatidae Diplodasyinae and Thaumastodermatinae are monophyletic and so are most genera. Oregodasys turns out to be the most basal group within Thaumastodermatinae in analyses of the concatenated data set as well as in analyses of the nuclear genes. Thaumastoderma appears as the sister taxon to the remaining species. Surprisingly, Tetranchyroderma is non-monophyletic in our analyses as one group of species clusters with Ptychostomella while another appears as the sister group of Pseudostomella.

    Conclusions/Significance

    Results in general agree with the current classification; however, a revision of the more derived thaumastodermatid taxa seems necessary. We also found that the ostensible COI sequences from several species do not conform to the general invertebrate or any other published mitochondrial genetic code; they may be mitochondrially derived nuclear genes (numts), or one or more modifications of the mitochondrial genetic code within Gastrotricha.

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