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The muscular system of Nemertoderma westbladi and Meara stichopi (Nemertodermatida, Acoelomorpha)
Department of Invertebrate Zoology, Swedish Museum of Natural History.ORCID iD: 0000-0001-8809-6753
Russian Academy of Sciences. (Zoological Institute)
Department of Invertebrate Zoology, Swedish Museum of Natural History.
2013 (English)In: Zoomorphology, ISSN 0720-213X, E-ISSN 1432-234X, Vol. 132, no 3, 239-252 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
New York/Heidelberg: Springer, 2013. Vol. 132, no 3, 239-252 p.
Keyword [en]
Nemertodermatida, Acoelomorpha, Musculature, Myogenesis, Phalloidin
National Category
URN: urn:nbn:se:su:diva-89583DOI: 10.1007/s00435-013-0191-6OAI: diva2:618699
Available from: 2013-04-29 Created: 2013-04-29 Last updated: 2014-10-28Bibliographically approved
In thesis
1. Through the magnifying glass - The big small world of marine meiofauna: Morphology, species and evolution in Nemertodermatida
Open this publication in new window or tab >>Through the magnifying glass - The big small world of marine meiofauna: Morphology, species and evolution in Nemertodermatida
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nemertodermatida is a group of microscopic marine worm-like animals that live as part of the marine meiofauna in sandy or muddy sediments; one species lives commensally in a holothurian. These benthic worms were thought to disperse passively with ocean currents, resulting in little speciation and thus wide or even cosmopolitan distributions. Individuals occur in low abundance and have few light microscopically available characters, which altogether may explain why only eight species had been described between the discovery of the taxon in 1930 and this thesis. We used molecular methods to address the diversity and phylogeny of this group for the first time. In a study of two nominal species with samples from all around the world, a high degree of cryptic speciation was discovered and several new species described. Diagnoses were based on molecular data complemented by morphological characters, where available. Given the patchy geographical record it can be assumed that the majority of the biodiversity of Nemertodermatida is yet to be described. A phylogenetic study including all but three known species revealed a deep divergence between the two families of Nemertodermatida but non-monophyly of the taxon was rejected by an Approximately Unbiased test.

Confocal laser scanning microscopic studies of several species show that the pattern of the body-wall musculature and the nervous system are specific for different genera. The muscular system of all species consists of a basic orthogonal grid with specific diagonal musculature and specialized muscles associated with body openings. The mouth appears to be transient feature in Nemertodermatida, developing only after hatching and being reduced again in mature worms. The nervous system is highly variable with very different ground patterns between the genera, such as an epidermal net, a centralized neuropile or a commissural brain.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2014. 41 p.
Nemertodermatida, Acoelomorpha, morphology, CLSM, Phalloidin, musculature, DNA, cryptic species, species delimitation, dispersal, taxonomy, phylogenetics, IHC, nervous system
National Category
Biological Systematics Zoology
Research subject
Systematic Zoology
urn:nbn:se:su:diva-107590 (URN)978-91-7447-986-7 (ISBN)
Public defence
2014-10-24, Stora Hörsalen, Naturhistoriska riksmuseet, Frescativägen 40, Stockholm, 13:00 (English)
Swedish Research Council, 2012-3913

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4. Manuscript.

Available from: 2014-10-02 Created: 2014-09-22 Last updated: 2014-11-18Bibliographically approved

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