Tardigrades of North America: New Records of Occurrence for Three Species of Green Tardigrades (Heterotardigrada, Echiniscoidea, Echiniscidae, Viridiscus)

Miller, William R.; McCowan, Penny J.; Perry, Emma S.; Schulze, Steven Louis; Shannon, Robynn K.; Henry, Charmaine B. S.

doi:10.1660/062.123.0122

Cited by 6 publications

(5 citation statements)

References 17 publications

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“…The complex of species previously known as the Echiniscus viridis group but currently classified in the recently erected genus Viridiscus has always drawn the attention of tardigrade taxonomists due to the persistence of the extraordinary green body pigmentation after mounting [ 15 – 18 , 20 , 38 ]. Despite the crucial revisions by Pilato et al [ 17 , 18 ], not all of the described Viridiscus spp.…”

Section: Discussionmentioning

confidence: 99%

The importance of being integrative: a remarkable case of synonymy in the genus Viridiscus (Heterotardigrada: Echiniscidae)

et al. 2021

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There are two predominant sources of taxonomically useful morphological variability in the diverse tardigrade family Echiniscidae: the internal structure and surface sculpture of the cuticular plates covering the dorsum (sculpturing) and the arrangement and morphology of the trunk appendages (chaetotaxy). However, since the appendages often exhibit intraspecific variation (they can be reduced or can develop asymmetrically), sculpturing has been considered more stable at the species level and descriptions of new echiniscid species based solely on morphology are still being published. Here, we present a case study in which a detailed analysis of the morphology and multiple genetic markers of several species of the genus Viridiscus shows that cuticular sculpture may also exhibit considerable intraspecific variation and lead to false taxonomic conclusions. In a population collected from the eastern Nearctic, in the type locality of the recently described species V. miraviridis, individuals with transitional morphotypes between those reported for V. viridissimus and V. miraviridis were found. Importantly, all morphotypes within the viridissimus–miraviridis spectrum were grouped in a single monospecific clade according to rapidly evolving markers (ITS-1, ITS-2 and COI). Given the morphological and genetic evidence, we establish V. miraviridis as a junior synonym of V. viridissimus. This study explicitly demonstrates that a lack of DNA data associated with morphological descriptions of new taxa jeopardizes the efforts to unclutter tardigrade systematics. Additionally, V. perviridis and V. viridissimus are reported from Lâm Đồng Province in southern Vietnam, which considerably broadens their known geographic ranges.

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Section: Discussionmentioning

confidence: 99%

The importance of being integrative: a remarkable case of synonymy in the genus Viridiscus (Heterotardigrada: Echiniscidae)

et al. 2021

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“…We update the genus phylogeny, and question the validity of V. clavispinosus , which we hypothesise to be a synonym of V. viridianus . We stress that there is no convincing evidence for the presence of V. viridis outside of the Hawaiian Archipelago 26 , and the Nearctic records 28 of this species are unreliable. The case of Viridiscus variability yet again illustrates that forming taxonomic conclusions based solely on morphology is unadvised and should be renounced 17 , especially since DNA sequence-based tools are readily available to incorporate into the systematics of these organisms.…”

Section: Introductionmentioning

confidence: 79%

“…Additional localities. North America, USA, New Mexico 23 ; the Azores, Ribeira Fria, Lages do Pico 23 , 29 , 30 ; North America, USA, New Jersey 28 ; Central America, the Lesser Antilles, Antigua 28 . Given the reported variability in the pattern of the dorsal armour, these additional localities should be verified.…”

Section: Resultsmentioning

confidence: 99%

Green armoured tardigrades (Echiniscidae: Viridiscus), including a new species from the Southern Nearctic, exemplify problems with tardigrade variability research

Momeni,

Gąsiorek,

Loeffelholz

et al. 2023

Sci Rep

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Ranges of tardigrade intraspecific and interspecific variability are not precisely defined, both in terms of morphology and genetics, rendering descriptions of new taxa a cumbersome task. This contribution enhances the morphological and molecular dataset available for the heterotardigrade genus Viridiscus by supplying new information on Southern Nearctic populations of V.perviridis, V.viridianus, and a new species from Tennessee. We demonstrate that, putting aside already well-documented cases of significant variability in chaetotaxy, the dorsal plate sculpturing and other useful diagnostic characters, such as morphology of clavae and pedal platelets, may also be more phenotypically plastic characters at the species level than previously assumed. As a result of our integrative analyses, V.viridianus is redescribed, V.celatus sp. nov. described, and V.clavispinosus designated as nomeninquirendum, and its junior synonymy with regard to V.viridianus suggested. Morphs of three Viridiscus species (V.perviridis, V.viridianus, and V.viridissimus) are depicted, and the implications for general echiniscid taxonomy are drawn. We emphasise that taxonomic conclusions reached solely through morphological or molecular analyses lead to a distorted view on tardigrade α-diversity.

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“…They use their piercing stylets and feeding straws (Fig. 1C, D) (32,33) for sucking up the chloroplasts inside the algae and moss protonema (3,34). These attempted cultures would invariably yield three generations of tardigrades at most before dying out.…”

Section: Resultsmentioning

confidence: 99%

How To Culture Limnoterrestrial Heterotardigrades: A Case Study In The Echiniscus, Pseudechiniscus And Viridiscus Genera

Momeni

Fuentes-González

Pienaar³

2021

Preprint

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Background: Tardigradologists have long tried to culture limnoterrestrial heterotardigrades without success. This is likely because they depend on specific conditions in their microhabitats. Most limnoterrestrial heterotardigrades are found associated with bryophytes and lichens (collectively cryptogams). In contrast to eutardigrades, many of which are easily cultured, heterotardigrades are found in cryptogams that prefer drier and sunnier habitats and that tend to grow on the vertical surfaces of boulders, cliffs, or tree trunks. By carefully observing heterotardigrades in the Echniscus and Viridiscus genera over many months, we determined that these organisms feed on chloroplasts and cytoplasm of both moss cells (typically moss protonema) and single-celled green algae associated with the moss (typically Chlorella vulgaris). We also determined that the cryptogams they associate with, and hence the heterotardigrades themselves, spend more time in a dried state than most eutardigrade species. Taking these observations into account we varied food, water, and desiccation cycle conditions with the aim of developing a culturing protocol for heterotardigrades. Results: We have maintained laboratory cultures of several generations and counting of Echiniscus, Pseudechniscus and Viridiscus genera tardigrades using the following experimentally derived protocol: Both moss and algae from their natural habitats are required as food sources and a small layer of rain or spring water is added every morning and allowed to evaporate some overnight. Furthermore, the organisms are more likely to lay eggs on a dense mat of moss protonema, grown by inserting tips of moss branches into a solidified KCM / agar medium. The medium also provides a walking substrate for the tardigrades, and possibly a source of cations. Crucially, the cultures must be allowed to dry out completely every ten days for a period of at least three days. Moss in the culture dish significantly improves the chances of the tardigrades coming out of their desiccation-resistant states successfully. Conclusions: We conclude that periodic drying out, moss and algae are all required to successfully culture heterotardigrades. Furthermore, drying must occur slowly, and the moss protonema enables this by retaining moisture thereby slowing evaporation. We suspect our protocol will work for most limnoterrestrial heterotardigrades with minor tweaking of culturing conditions.

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Tardigrades of North America: New Records of Occurrence for Three Species of Green Tardigrades (Heterotardigrada, Echiniscoidea, Echiniscidae, Viridiscus)

Cited by 6 publications

References 17 publications

The importance of being integrative: a remarkable case of synonymy in the genus Viridiscus (Heterotardigrada: Echiniscidae)

The importance of being integrative: a remarkable case of synonymy in the genus Viridiscus (Heterotardigrada: Echiniscidae)

Green armoured tardigrades (Echiniscidae: Viridiscus), including a new species from the Southern Nearctic, exemplify problems with tardigrade variability research

How To Culture Limnoterrestrial Heterotardigrades: A Case Study In The Echiniscus, Pseudechiniscus And Viridiscus Genera

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