Current knowledge on Mexican tardigrades with a description of Milnesium cassandrae sp. nov. (Eutardigrada: Milnesiidae) and discussion on the taxonomic value of dorsal pseudoplates in the genus Milnesium Doyère, 1840

Abstract

Mexico is a megadiverse country, however its tardigrade fauna is poorly known and to date 44 species have been reported from this region. In the present paper, an update of the reported Mexican tardigrades is presented, increasing the number of recorded tardigrades to 55 species (11 new records). Moreover, we describe Milnesium cassandrae sp. nov. from State of Nuevo León in northern Mexico. The new species is most similar to Mil. krzysztofi Kaczmarek & Michalczyk, 2007 and Mil. beasleyi Kaczmarek, Jakubowska & Michalczyk, 2012, but it differs from them mainly by details of the dorsal sculpture and some morphometric characters. We also discuss the taxonomic value of a recently described feature, ‘pseudoplates’, for differentiating the taxa within the genus Milnesium Doyère, 1840. [Zoobank URL: urn:lsid:zoobank.org:act:0684AE18-0510-4F7B-B75D-AE5177FBF2A2]

Milnesium (Tardigrada: Apochela) in Japan: The First Confirmed Record of Milnesium tardigradum s.s. and Description of Milnesium pacificum sp. nov.

“…Milnesium pacificum sp. nov. has dorsal cuticular sculpturing characteristic of the granulatum group in this genus, which consists of the following seven species described prior to the present study: M. granulatum Ramazzotti, 1962, Milnesium reticulatum Pilato et al, 2002, Milnesium katarzynae Kaczmarek et al, 2004, Milnesium krzysztofi Kaczmarek and Michalczyk, 2007, Milnesium alabamae Wallendorf and Miller, 2009 (for the five species above, see Morek et al, 2019a), and additionally Milnesium lagniappe and Milnesium cassandrae Moreno-Talamantes et al, 2019, which should also be included in the granulatum group. We must consider that M. katarzynae, for example, was described with only two specimens, both of which might have been hatchlings (294.5 and 285.0 μm, respectively, in body length, Kaczmarek et al, 2004; also see Morek et al, 2016;Surmacz et al, 2020).…”

“…nov. show positive, negative and sexual CC changes. drae) was found in Mexico (Moreno-Talamantes et al, 2019;Fig. 13).…”

“…Moreover, M. alpigenum was integratively redescribed, which now allows for a confident identification of the species (Morek et al, 2019b). Presently, more than 40 species of the genus Milnesium have been described (Degma et al, 2019;Kaczmarek et al, 2019;Surmacz et al, 2019;Moreno-Talamantes et al, 2019).…”

Rough backs: taxonomic value of epicuticular sculpturing in the genus Milnesium Doyère, 1840 (Tardigrada: Apochela)

“…, 2004 23 ; M. krzysztofi ; M. alabamae Wallendorf & Miller, 2009 24 ; M. lagniappe Meyer, Hinton & Dupré, 2013 25 ; M. cassandrae Moreno-Talamantes et al . , 2019 26 ; and M. pacificum Sugiura et al . , 2020 27 .…”

Novel integrative data for two Milnesium Doyère, 1840 (Tardigrada: Apochela) species from Central Asia

“…Additionally, in contrast to parachelans, apochelans lack important morphological characters commonly utilised in their taxonomy, for example, placoids and septulum in the muscle pharynx or ornamented egg shells. The great majority of extant species (41 of 44) within the family Milnesiidae Ramazzotti, 1962, the only one in order Apochela, are classified within genus Milnesium Doyère, 1840(37 listed in Degma et al 2009, excluding two nomina dubia: M. dujiangensis and M. tardigradum trispinosa, but with a further four taxa described later on by Kaczmarek et al 2019, Moreno-Talamantes et al 2019, and Surmacz et al 2019. Due to the limited number of taxonomically meaningful traits the classification of this genus is challenging and, so far, has been based mostly on classical morphological data that were shown to be at least partially insufficient in resolving the taxonomy of these tardigrades, as pseudocryptic species have recently started to be recognised (e.g.…”