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

Abstract

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 desiccationsensitive tardigrades, especially for comparative molecular analyses of anhydrobiosis mechanisms.

DNA Protection Protein, a Novel Mechanism of Radiation Tolerance: Lessons from Tardigrades

“…Currently, approximately 1200 species have been reported from various habitats, such as marine, fresh-water, or limno-terrestrial environments, though the real number of tardigrade species is estimated to be much higher [ 4 , 5 ]. Tardigrades were found in harsh environments such as Antarctica as well as in urban area, e.g., from activated sludge in a sewage treatment plant [ 6 , 7 , 8 ]. All tardigrades require surrounding water to grow and reproduce, but some limno-terrestrial species are able to tolerate almost complete dehydration.…”

Comparison of the transcriptomes of two tardigrades with different hatching coordination

“…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]). The small variance in H. exemplaris is similar to the limnic species Isohypsibius myrops [19]. It is worth noting that the R. varieornatus strain YOKOZUNA-1 was derived from a single individual [18], suggesting that genetic variation would not be higher than H. exemplaris , and therefore the hatching time variability is not due to the genetic variability.…”

Parallel evolution of trehalose production machinery in anhydrobiotic animals via recurrent gene loss and horizontal transfer

“…TYO ; their morphology was consistent with the descriptions of Paramacrobiotus in the literature [ 47 ]. For breeding, we reared the tardigrade individuals in a thin water layer on 1.2% agar plates at 22°C, and fed them a mixture of algae, Chlorella vulgaris (Chlorella Industry Co., Japan, or Recenttec K. K., Japan), and small monogonont rotifers, Lecane inermis, in a manner similar to that described for other tardigrades [ 48 ].…”