Redescription of Antarctic eutardigrade Dastychius improvisus (Dastych, 1984) and some remarks on phylogenetic relationships within Isohypsibioidea

Abstract

In the present paper, we examined the type material as well as newly collected specimens of the rare Antarctic eutardigrade species -Dastychius improvisus. Based on the available material, we prepared a full re-description of this species emending its description with new morphometrical characters. We conducted also phylogenetic analyses based on 18S and 28S rRNA sequence data and showed the position of the genus Dastychius in the family Isohypsibiidae. Moreover, we indicated that phylogenetic relationships within the superfamily Isohypsibioidea are still unresolved. This problem is mainly related to the relatively limited number of available sequences for the species from Isohypsibioidea and incorrectly identified sequences deposited in genetic databases, e.g. from the genus Eremobiotus. Finally, we also discussed the status of several members of Isohypsibioidea.

End of a mystery: Integrative approach reveals the phylogenetic position of an enigmatic Antarctic tardigrade genus Ramajendas (Tardigrada, Eutardigrada)

“…were clustered together with a good support in both trees (0.97 in BI). This result of present study agrees with the findings of Mioduchowska et al (2021). The subclade (Eremobiotus + (I. dastychi + D. improvisus)) was clustered with the genus Ursulinius with a good support, which also agrees with previous findings Mioduchowska et al, 2021).…”

“…The family Halobiotidae was revealed as a sister group to the Doryporibiidae + Hexapodibiidae complex by but clustered with the Isohypsibiidae in Mioduchowska et al (2021). In the latter study, the Hexapodibiidae appeared as a highly derived group within a complex of taxa constituting most of the paraphyletic group Doryphoribiidae.…”

“…The ranges of uncorrected genetic p-distances between the studied specimen of R. frigidus and other Isohypsibioidea species (see Data S1) were 17.55%-24.23% (mean 22.06%), with Thulinius stephaniae (Pilato, 1974) (EF620417, Møbjerg The results of this study were compared with the phylogenetic trees reconstructed by and Mioduchowska et al (2021). To note, while the set of the species included in the analyses in those two studies was similar, the phylogenetic trees had a different configuration (Figure 4, Alignments S2 and S3).…”

“…The family Isohypsibiidae was monophyletic with a weak support in both previous studies, but its position was very different. In , the Isohypsibiidae clade was recognized as a sister group (Clade I) to the monophyletic complex consisting of all the other Isohypsibioidea (Clade II), while in Mioduchowska et al (2021), the Isohypsibiidae clade appeared as a highly derived group closely related to the Halobiotidae. In general, the well-supported monophyletic complex ((Doryporibiidae + Hexapodibiidae) + H alobiotidae + Ramajendidae fam.…”

“…According to , Ramajendas belongs in the family Ramazzottiidae (Hypsibioidea) because of the similarity of its claw morphology with that in Ramazzottius Binda & Pilato, 1986. On the other hand, it can be attributed to the superfamily Isohypsibioidea based on the AISM structure, as proposed by Marley et al (2011) and Zawierucha et al (2018), and later accepted by Guidetti et al (2019) and Mioduchowska et al (2021).…”