2026/03/14 by Marc Mapalo, Suhrid Ghosh, Elizabeth A Gavrilov +2 · 1 voice
Agricultural and Biological Sciences · Physics and Astronomy · Environmental Science · #Tardigrade Biology and Ecology #Laser-Plasma Interactions and Diagnostics #Polar Research and Ecology
paper · doi:10.1093/zoolinnean/zlag056
openalex publication_date 2026/03/14 · openalex created_date 2026/04/16 · openalex updated_date 2026/06/22
Abstract Tardigrades are microinvertebrates, whose body plan consists of a head region followed by four segments, each bearing a pair of lobe-like legs. Most tardigrades lack a posterior extension or tail beyond the last pair of legs. However, studies of the eutardigrade Hypsibius exemplaris Gąsiorek, Stec, Morek & Michalczyk, 2018 indicate that embryos show evidence for a tail region that disappears during development. Here, we determined the gene expression patterns of the posterior marker caudal (cad) and the gut marker forkhead (fkh) in H. exemplaris to understand the identity and fate of this disappearing region. Results showed that cad is expressed in the tail region when this structure is still visible in the embryo; however, cad expression appears more anteriorly when the tail disappears at a later stage. A similar pattern was observed with the posterior end of fkh expression. These observations are consistent with the hypothesis that the posterior extension develops into the hindgut. We hypothesize that the anterior migration of this region might be associated with the repositioning of the last pair of legs, potentially contributing to their rotated phenotype. Comparisons with the other panarthropods suggest that their common ancestor had a tail-like posterior extension, and the tail of H. exemplaris embryos might represent a remnant structure of its deep evolutionary history.