Ultraviolet radiation tolerance in hydrated and desiccated eutardigrades

Abstract

So far, most studies on tardigrade resistance to extreme stresses have focused on their responses to several chemical and physical extremes, but there is still a paucity of data regarding the tardigrade responses to ultraviolet radiation. Considering also the future perspectives offered by space flights, we compared the biological responses of two eutardigrade species (Paramacrobiotus richtersi and Ramazzottius oberhaeuseri) to UV irradiation, alone or in combination with multiple stressors (temperature and air relative humidity) in two different physiological conditions (desiccated and hydrated states). Tardigrades were exposed to seven different UV doses (from 10.32 up to 87.72 kJ m )2 ) in a controlled climatic chamber. The results showed that active and anhydrobiotic tardigrades were able to withstand high doses of ultraviolet radiations. The survival rate of hydrated or desiccated specimens of both species was inversely related to the UV doses, with P. richtersi that better tolerated the increase of UV dose than R. oberhaeuseri. Surprisingly, the tolerance to physical and chemical extreme stresses is not an exclusive property of desiccated tardigrades; in certain environmental conditions (high air humidity level or low temperature), desiccated tardigrades have a lower or similar ability to withstand UV irradiation than hydrated ones. This represents a further demonstration of the uniqueness of this animal group in tolerating extreme stresses. In addition, we demonstrated that high temperatures have a strong impact on tardigrade survival during UV exposition both in hydrated and desiccated animals.

Tardigrades Use Intrinsically Disordered Proteins to Survive Desiccation

“…P. richtersi specimens were desiccated by placing each group of animals on a Whatman filter paper (25 mm 2 or 1 cm 2 ) with mineral water (9 μl or 30 μl, respectively) and exposing them initially to 80% relative humidity (RH) and 18°C for 4 hr, then to 50% RH at 18°C for 4 hr in a climatically controlled chamber, and finally to 0%–3% RH at room temperature for 12 hr (Altiero et al, 2011). At the end of this treatment animals exhibit the typical tun shape.…”

Mechanisms of animal diapause: recent developments from nematodes, crustaceans, insects, and fish

“…However, relatively little attention has been focused on maintenance of genome integrity during embryonic diapause, and how DNA damage may affect survival of dormant embryos. This is an important concept to explore, especially considering that some believe accumulated DNA damage may limit the life span of dormant anhydrobiotic organisms, such as tardigrades (139), despite their ability to withstand rather massive doses of UV radiation (2).…”

Tolerance to gamma-irradiation in eggs of the tardigrade Richtersius coronifer depends on stage of development

“…Adult tardigrades survive several thousand Gray, with an LD 50 dose of 4-6 kGy observed 1-2 days after irradiation. They also tolerate high doses of UV radiation (Altiero et al, 2011). Of particular interest is the fact that in all studies so far, including studies on X-ray, alpha, gamma and UV radiation, desiccated and hydrated tardigrades show similar survival.…”