Integrative redescription of a common Arctic water bear Pilatobius recamieri (Richters, 1911)

• Published in: Polar Biology
• Main Authors: Gąsiorek, Piotr, Zawierucha, Krzysztof, Stec, Daniel, Michalczyk, Łukasz
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: biodiversity; Hypsibiidae; microfauna; Pilatobius secchii nom. inq; Svalbard; Tardigrada; Arctic; Polar Biology; Tundra; Tardigrade; water bear
• Online Access: https://ruj.uj.edu.pl/xmlui/handle/item/46714; https://doi.org/10.1007/s00300-017-2137-9

Tardigrada are a group of microscopic metazoans that inhabit a variety of ecosystems throughout the world, including polar regions, where they are a constant element of microfauna with densities exceeding hundreds of individuals per gram of dry plant material. However, despite a long history of research and their ubiquity in tundra ecosystems, the majority of tardigrade species have limited and outdated diagnoses. One such example is Pilatobius recamieri, a common tardigrade that is widely distributed in the Arctic. The aim of this study is to redescribe this species using new material from the type locality and tools of integrative taxonomy, viz. by combining classical imaging and morphometry by light microscopy and scanning electron microscopy imaging with DNA sequencing of four markers with various mutation rates: three nuclear (18S rRNA, 28S rRNA, and ITS-2) and one mitochondrial (COI). The sequences of the three latter markers are also the first to be presented for the genus Pilatobius. This study therefore provides the first necessary step towards the verification of the geographic range of P. recamieri, which is currently assumed to be very broad. A detailed comparison of P. recamieri with Pilatobius secchii (Bertolani and Rebecchi, 1996) from Italy revealed no morphological or morphometric differences between the two species, thus we designate P. secchii as a nomen inquirendum until molecular data for the taxon become available. Finally, we propose to replace the term "lunula" in the superfamilies Hypsibioidea and Isohypsibioidea with the more appropriate "pseudolunula" to differentiate it from the true lunula in other parachelans.