Figure 2.

Intensity of fluorescence signal emitted by storage cells of the tardigrade Paramacrobiotus spatialis as a marker of ROS production, detected 3 h and 12 h after the rehydration process (R) in animals kept in a desiccated state (D) for 1 day and 20 days, using the fluorescent probe 2,7-dichlorodihydrofluorescein diacetate (DCFH₂-DA). (a) Hydrated animals (control). (b) Animals kept in a desiccated state for 1 day (3 h after rehydration process). (c) Animals kept in a desiccated state for 1 day (12 h after rehydration process). (d) Animals kept in a desiccated state for 20 days (3 h after rehydration process). (e) Animals kept in a desiccated state for 20 days (12 h after rehydration process). (a–e) Scale bars = 10 µm. (f) Each column represents the mean value of the fluorescence intensity emitted by the storage cells for each experimental group. The total number (n) of measured cells is: Ctr, n = 138; D 1 R 3, n = 46; D 1 R 12, n = 78; D 20 R 3, n = 78; D 20 R 12, n = 36 (see (see Table S1). The bar on each column represents standard deviation. Different letters above each column indicate significant differences in the fluorescence signals among the different experimental conditions. a.u. = arbitrary unit. D 1 = animals kept in a desiccated state for 1 day, D 20 = animals kept in a desiccated state for 20 days, R 3 = 3 h after the rehydration process, R 12 = 12 h after the rehydration process, Ctr = control animals. The storage cells of desiccated animals always emitted an intense fluorescence signal, while those of control ones emitted a faint spotted fluorescence signal (Fig. 2). The intensity of the fluorescence signal emitted by the storage cells of desiccated animals was always significantly higher than the fluorescence intensity detected in cells of control animals (Fig. 2; Table 1; one-way ANOVA: n = 485; p < 0.001). Moreover, the intensity of the fluorescence signal was at its highest level in the coelomocytes of animals kept desiccated for 20 days, while the lowest signal was recorded in cells of tardigrades kept desiccated for 1 day (Fig. 2; Table 1).