Establishment of an isogenic strain of the desiccation-sensitive tardigradeIsohypsibius myrops(Parachela, Eutardigrada) and its life history traits

Tardigrades are aquatic micrometazoans found in various habitats. Many limno-terrestrial species can tolerate desiccation by entering a metabolically inactive dehydrated state called anhydrobiosis, whereas most species in constantly hydrated habitats, such as freshwater or marine species, cannot undergo anhydrobiosis and are susceptible to desiccation. Although comparative analyses between anhydrobiotic species and desiccation-sensitive species will lead to a better understanding of anhydrobiosis, almost all studies on anhydrobiosis have been performed only in anhydrobiotic species. In the present study, we established a rearing system and an isogenic strain of Isohypsibius myrops collected from activated sludge. This strain is highly sensitive to desiccation and cannot tolerate exposure to relative humidity (RH) of 97–98% for 2 days or 94–95% for 1 day. Life history traits revealed that this strain has a short hatching time (3.6 days) and a short lifespan (18.8 days). The strain frequently lays eggs, on average 19 eggs per oviposition at mean interval of 2.5 days, enabling their rapid proliferation. The high fecundity of desiccation-sensitive species implies a possible trade-off between anhydrobiotic ability and fecundity. The established strain provides a good experimental model of desiccation-sensitive tardigrades, especially for comparative molecular analyses of anhydrobiosis mechanisms.