Studies have indicated an increase of ultraviolet radiation (UVR) at high elevations. Thus, aquatic invertebrates found in habitats at higher elevations are exposed to increased UVR which may negatively impact lifespan and fecundity. In response to environmental stressors, bdelloid rotifers can enter a state of anhydrobiosis by compacting cellular structures, reducing metabolic activities, and forming a xerosome. A complementary strategy is found in bdelloid rotifers, Pleuretra lineata, occurring in rock pools (huecos) located in Hueco Tanks State Park and Historic Site, El Paso Co., TX (elevation: 1375 m; have UVR intensity). This species has shown resistance to UVR likely due to red pigmentation. Under natural conditions, bdelloids are highly pigmented (HP). When cultured in the laboratory, they become moderately pigmented (MP) after 2 weeks, lightly pigmented (LP) after 6 weeks, and essentially lacking pigment (NP) after 24 weeks. This study investigates how resistance to UVR compares among rotifers with HP, MP, LP, and NP. To mimic natural conditions as rock pools dry, rotifers were desiccated for 1 or 7 days, then exposed to low (130 µW/cm2), mid (375 µW/cm2), or high (500 µW/cm2) UVR for 2 hr. Survival was assessed 48 hrs after exposure.
Results/Conclusions
Preliminary results indicated that NP rotifers desiccated for 1-day and exposed to low UVR had the highest survival (mean% ± SE: 65±5). NP rotifers desiccated for 7-days and exposed to high UVR had the lowest survival (28±5). When compared to a previous study, NP rotifers had a similar survival response to LP rotifers at: 1-day desiccation at low (NP, LP: 68.5±1.5, 68.5±1.5), mid (57.5±6, 48.4±1.2), and high (55.5±3.6, 40.1±0.8) UVR intensities. 7-day desiccation results were as follows for low (NP, LP: 61.7±2.2, 61.3±0.2), mid (44±2.9, 46.5±1.5), and high (28±2.6, 2.9±0.1) UVR. Survival decreased as desiccation time increased and as UVR intensity increased. Additional replicates are needed to provide statistical power to determine if there is a difference in recovery. The similarities in survival between NP and LP rotifers may be due to some residual pigmentation in NP. Future work will include a desiccation control (0-day) and 32-day desiccation for all pigment levels. This study will provide an understanding on how bdelloids rotifers may use pigmentation as an adaptation for protection against UVR levels; this may become increasingly important as the climate changes.