Comparison of the transcriptomes of two tardigrades with different hatching coordination

Yuki Yoshida,Kazuharu Arakawa,Midori Matsumoto,Kenta Sugiura,Masaru Tomita

doi:10.1186/s12861-019-0205-9

Yuki Yoshida, Kazuharu Arakawa + Show 3 more

Open Access

https://doi.org/10.1186/s12861-019-0205-9

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Abstract

BackgroundTardigrades 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.ResultsTo 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.ConclusionThese observations suggest a hatching regulation mechanism by the molting pathway in H. exemplaris.

Highlights

Tardigrades are microscopic organisms, famous for their tolerance against extreme environments
We assume that hatching related genes may be upregulated around Egg 3d and 5d in H. exemplaris and R. varieornatus, respectively
We have observed that the H. exemplaris embryo hatches in a strictly controlled manner within a short time range (4.03 ± 0.50 days) compared to the wider range observed in R. varieornatus (5.72 ± 1.13 day, see [18])

Summary

Introduction

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. 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. The establishment of rearing systems for several species has enabled various quantitative zoological and molecular analyses, mainly focused on the limnic Hypsibius exemplaris and terrestrial Ramazzottius varieornatus [14, 18]. Higher diversity in hatching timing of in-lab cultures which lack non-predictable stimuli (i.e. environmental factors) suggests that the diversity may be the result of adaptation to their living habitat

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