Phylum Tardigrada

Nelson, Diane R.

doi:10.1016/b978-0-12-385026-3.00017-6

Cited by 146 publications

(73 citation statements)

References 54 publications

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“…Tardigrades, also known as water bears, are a phylum of microscopic invertebrates that dwell in marine, freshwater and terrestrial ecosystems (Nelson et al 2015). The first formal descriptions of tardigrade species were published in the first half of the XIX century.…”

Section: Introductionmentioning

confidence: 99%

Redescription of Milnesium alpigenum Ehrenberg, 1853 (Tardigrada: Apochela) and a description of Milnesium inceptum sp. nov., a tardigrade laboratory model

Morek

Suzuki

Schill

et al. 2019

Zootaxa

759

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Intra- and interspecific variability, being at the very core of alpha taxonomy, has been a long-standing topic of debate among tardigrade taxonomists. Early studies tended to assume that tardigrades exhibit wide intraspecific variation. However, with more careful morphological studies, especially those incorporating molecular tools that allow for an independent verification of species identifications based on phenotypic traits, we now recognise that ranges of tardigrade intraspecific variability are narrower, and that differences between species may be more subtle than previously assumed. The taxonomic history of the genus Milnesium, and more specifically that of the nominal species, M. tardigradum described by Doyère in 1840, is a good illustration of the evolution of views on intraspecific variability in tardigrades. The assumption of wide intraspecific variability in claw morphology led Marcus (1928) to synonymise two species with different claw configurations, M. alpigenum and M. quadrifidum, with M. tardigradum. Currently claw configuration is recognised as one of the key diagnostic traits in the genus Milnesium, and the two species suppressed by Marcus have recently been suggested to be valid. In this study, we clarify the taxonomic status of M. alpigenum, a species that for nearly a century was considered invalid. We redescribe M. alpigenum, using a population collected from the locus typicus, by the means of integrative taxonomy, i.e. including light microscopy, scanning electron microscopy, ontogenetic observations, and genetic barcoding. Moreover, the redescription of M. alpigenum allowed us to verify the uncertain taxonomic status of two popular laboratory models that were originally considered to be M. tardigradum; though one was recently reidentified as M. cf. alpigenum. Our analysis showed that both laboratory strains, despite being morphologically and morphometrically nearly identical to M. alpigenum, in fact represent a new species, M. inceptum sp. nov. The two species, being disnguishable only by statistical morphometry and/or DNA sequences, are the first example of pseudocryptic species in tardigrades.

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Section: Introductionmentioning

confidence: 99%

Redescription of Milnesium alpigenum Ehrenberg, 1853 (Tardigrada: Apochela) and a description of Milnesium inceptum sp. nov., a tardigrade laboratory model

Morek

Suzuki

Schill

et al. 2019

Zootaxa

759

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“…As an immense fraction of the world's biodiversity remains unexplored (Mora et al 2011), especially within the taxonomic groups belonging to aquatic meiofauna and limno-terrestrial microfauna, degradation of so unique ecosystems threatens many organisms. Tardigrades are micrometazoans that can be found both in sea and land habitats (Nelson et al 2015), constituting an important portion of local species…”

Section: Introductionmentioning

confidence: 99%

New Echiniscidae (Heterotardigrada) from Amber Mountain (Northern Madagascar)

Gąsiorek¹,

Vončina²

2019

EvolSyst

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A moss sample from the local biodiversity hotspot in lowland rainforest in the vicinity of Amber Mountain, Madagascar, yielded the discovery of twoEchiniscusC.A.S. Schultze, 1840 species, of which one is new to science.Echiniscussuccineussp. nov.is related to other members of thespinulosusgroup, but differs from them by the highly complicated structure of the dorsal plates, with intricately thickened parts of the armour forming ornamented pattern. The validity of the intraporal dark rings as a taxonomic trait is discussed in the context of the recovered intraspecific variability for the new taxon. Besides, rareEchiniscusafricanusMurray, 1907 is reported for the first time from the island.

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“…Among tardigrades (water bears), herbivorous species feed on bacteria and algal cells or suck fluids from plant cells, such as mosses, whereas predatory tardigrades feed on protozoa, rotifers, nematodes or even other tardigrades (Avdonina et al ., ; Nelson, Guidetti & Rebecchi, ). Most of the body of a tardigrade is filled by a gut and a gonad (especially during the advanced stages of oogenesis).…”

Section: Introductionmentioning

confidence: 99%

Ultrastructural changes in the midgut epithelium ofHypsibius dujardini(Doyère, 1840) (Tardigrada, Eutardigrada, Hypsibiidae) in relation to oogenesis

et al. 2016

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In Hypsibius dujardini (Doy ere, 1840), the endodermal region of the digestive system, which is called the midgut, spreads along the entire length of the body. Its wall is formed by a simple epithelium that is composed of digestive cells. In this paper, we present the first report on the presence of two groups of midgut regenerative cells that form two 'epithelial rings'anterior and posterior. Additionally, we observed the proliferative abilities of the midgut regenerative cells, thus confirming the statement that they play the role of midgut stem cells. The precise ultrastructure of the digestive and regenerative cells was determined using transmission electron microscopy. Changes in the digestive and regenerative cells were correlated with the different stages of oogenesis. The process of oogenesis in H. dujardini took 4 days (at a temperature of 16°C). Reserve material gradually accumulated in the cytoplasm of the digestive cells and histochemical staining showed that it primarily contained proteins, polysaccharides and a small quantity of lipids. The reserve material accumulated during vitellogenesis, and it began to decrease during choriogenesis. During the simplex stage, when the entire buccalpharyngeal apparatus was expelled from the body, the stages of oogenesis were advanced, the midgut was much reduced, and the reserve material was exploited by the animal.

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Phylum Tardigrada

Cited by 146 publications

References 54 publications

Redescription of Milnesium alpigenum Ehrenberg, 1853 (Tardigrada: Apochela) and a description of Milnesium inceptum sp. nov., a tardigrade laboratory model

Redescription of Milnesium alpigenum Ehrenberg, 1853 (Tardigrada: Apochela) and a description of Milnesium inceptum sp. nov., a tardigrade laboratory model

New Echiniscidae (Heterotardigrada) from Amber Mountain (Northern Madagascar)

Ultrastructural changes in the midgut epithelium ofHypsibius dujardini(Doyère, 1840) (Tardigrada, Eutardigrada, Hypsibiidae) in relation to oogenesis

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