Two new species of Tardigrada from moss cushions (Grimmia sp.) in a xerothermic habitat in northeast Tennessee (USA, North America), with the first identification of males in the genus Viridiscus

Abstract

Background The phylum Tardigrada consists of over 1,300 species that inhabit terrestrial, freshwater and marine environments throughout the world. In terrestrial habitats they live primarily in mosses, lichens, leaf litter and soil, whereas tardigrades in freshwater and marine environments are mainly found in sediments and on aquatic plants. More than 65 species have been previously reported in the state of Tennessee, USA. Methods Tardigrades present in moss cushions (Grimmia sp.) collected from a xerothermic habitat on the East Tennessee State University campus, Johnson City, TN, USA, were extracted, mounted on slides, identified, and counted. Additional samples of fresh dried moss were used for integrative analyses, including morphological analysis with phase contrast (PCM) and scanning electron microscopy (SEM), as well as molecular analyses of COI, 18S rRNA, 28S rRNA, and ITS-2 of the Macrobiotus and Milnesium species. Results Five species were found, including two species new to science: Viridiscus miraviridis sp. nov. and Macrobiotus basiatus sp. nov. Viridiscus miraviridis sp. nov. differs from other members of the genus mainly by having a different type of dorsal cuticle and some other, more subtle, morphometric characters. In addition to the two new species, Viridiscus perviridis and Viridiscus viridissimus were present, and males of Vir. viridissimus were found for the first time, the first record of males in the genus Viridiscus. Macrobiotus basiatus sp. nov. is most similar to Macrobiotus nelsonae, but it differs from Mac. nelsonae mainly by the stylet supports being situated in a more anterior position, shorter and narrower egg processes, and a smaller number of areoles around the egg processes. Moreover, the identification of Milnesium inceptum was confirmed as the first record for the USA by analysis of COI.

“Everything is not everywhere”: Time‐calibrated phylogeography of the genus Milnesium (Tardigrada)

“…Interestingly, M . inceptum seems to be an example of a cosmopolitan taxon, as it has been reported from five continents and an oceanic island (Europe and Far East Asia in Morek, Suzuki, et al, 2019 ; Australia in Morek & Michalczyk, 2020 ; North America in Nelson et al, 2020 ; and South Africa and New Zealand in the present contribution). In all five cases, M .…”

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

“…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.…”

“…Individuals with such long cirri may have prompted Maucci [ 39 ] to identify North American Viridiscus specimens as V. perviridis . Likewise, Nelson et al [ 20 ] identified Tennessee specimens with long cirri as V. perviridis . However, given that the Tennessee specimens analyzed in this study with perviridis -like long cirri exhibited viridianus -like sculpturing, we identified them as V. aff.…”

“…In the redescription of the type species Viridiscus viridis [ 19 ], Pilato et al [ 18 ] highlighted morphological differences in dorsal sculpturing between the known representatives of Viridiscus . Last year, a new Nearctic species, Viridiscus miraviridis, was described based on its extraordinarily developed epicuticular layer forming sclerotized ridges, a character previously unknown in the genus [ 20 ]. However, attempts to obtain DNA barcode data were unsuccessful, so the original description was based solely on morphological characters.…”

Integrative descriptions of two new Macrobiotus species (Tardigrada, Eutardigrada, Macrobiotidae) from Mississippi (USA) and Crete (Greece)

“…Faunistic and taxonomic studies on the tardigrades of North America are numerous and both local and continental species lists have been compiled (Meyer 2013;Kaczmarek et al 2016). It is, however, clear from new species in the USA being described (see for example Nelson et al 2020a), that we are still far from a complete knowledge of the taxonomic diversity of tardigrades in this country. In particular, the tardigrade fauna in the state of Mississippi (USA) has been investigated only once by Hinton and Meyer (2009) who reported only 9 species (from 20 samples).…”