Water bear with barbels of a catfish: A new Asian Cornechiniscus (Heterotardigrada: Echiniscidae) illuminates evolution of the genus

Abstract

Cornechiniscus Maucci & Ramazzotti, 1981 is a species-poor heterotardigrade genus with peculiar, horn-shaped appendages A. It can be found in mosses and lichens growing on dusty soils on all continents except for Australasia and Antarctica, with presumably Central Asia as the main place of species radiation. A recent, COI and ITS-1-based phylogeny elucidated phylogenetic relationships between 5 out of 10 Cornechiniscus species, and aided the integrative description of C. imperfectus Gąsiorek & Michalczyk, 2020 from mountains of Northern Kyrgyzstan. However, the other 5 species remained unplaced on the generic evolutionary tree. Using new samples from Northern Kyrgyzstan, Italy and Argentina, I extracted new representatives of the genus and updated the genus phylogeny in the frame of integrated taxonomic approach (light and scanning microscopy, DNA sequencing of four markers: 18S rRNA, 28S rRNA, ITS-1, and COI). A new Kyrgyz species is dioecious and necessitates modifying the genus diagnosis to accommodate its cirri prolongation that contrasts with bulbous peribuccal cirri typical for Cornechiniscus. Furthermore, it enhances the hypothesis on the Central Asian origin of the genus. Morphologically, C. mystacinussp. nov. most closely resembles C. tibetanus (Maucci, 1979) by its large body size (adult females ∼500 μm on average), strongly heteronych and smooth claws, and by the development of spines in the lateral positions C–E and at the posterior margin of the pseudosegmental plate IV’. I demonstrated the sister relationship between C. holmeni (Petersen, 1951) and C. imperfectus, previously hypothesised based on their morphological similarity. Cornechiniscus lobatus (Ramazzotti, 1943) can be considered a subcosmopolitan taxon since it certainly occurs in the Holarctic and Neotropics.