Project description:Tardigrades are microscopic organisms, famous for their tolerance against extreme environments. The establishment of rearing systems of multiple species has allowed for comparison of tardigrade physiology, in particular in embryogenesis. Interestingly, in-lab cultures of limnic species showed smaller variation in hatching timing than terrestrial species, suggesting a hatching regulation mechanism acquired by adaptation to their habitat. To this end, we screened for coordinated gene expression during the development of two species of tardigrades, Hypsibius exemplaris and Ramazzottius varieornatus, and observed induction of the arthropod molting pathway. Exposure of ecdysteroids and juvenile hormone analog affected egg hatching but not embryonic development in only the limnic H. exemplaris. These observations suggest a hatching regulation mechanism by the molting pathway in H. exemplaris.
Project description:Limno-terrestrial tardigrades enter a state called anhydrobiosis when exposed to desiccation, and acquire tolerance against various extreme environments. The anhydrobiotic tardigrade Hypsibius dujardini, is a non-pigmented tardigrade easy to culture and RNAi method have been established, therefore making it a model tardigrade for tardigrade molecular research. Previous genome assemblies of this tardigrade had increased size due to heterozygosity. Here, we have sequenced the genome of H. dujardini using single individual Illumina DNA-Seq data and PacBio long read data, and employed a heterozygosity aware assembly method to assemble a near-complete high quality genome. In order to annotate the genome with gene predictions, we conducted RNA-Sequencing of various stages of developmental, juvenile, adult, and anhydrobiotic stage H. dujardini and Ramazzottius varieornatus, a tardigrade capable of rapid anhydrobiosis entry, and used these data for gene prediction with BRAKER v1.9 or differential gene expression analysis of the active and anhydrobiotic stages.
