Fischer Janet M, Fields Peter A, Pryzbylkowski Peter G, Nicolai Jaclyn L, Neale Patrick J
Department of Biology, Franklin & Marshall College, Lancaster, PA, USA.
Photochem Photobiol. 2006 Mar-Apr;82(2):547-50. doi: 10.1562/2005-08-30-RA-664.
We examined the effects of UV radiation (UVR) on metabolic rates of the freshwater cladoceran Daphnia catawba. We exposed D. catawba to UVB for 12 h in a lamp phototron at levels of 2.08 and 4.16 kJ m(-2) both with and without concomitant exposure to UVA and visible photorepair radiation (PRR). We also included a group that received PRR only and a dark control group. Respiration rates were measured for 6 h following exposure. Respiration rates increased by 31.8% relative to the dark control at the lowest level of UVB stress (2.08 kJ m(-2) UVB with PRR), whereas respiration was inhibited by 70.3% at the highest stress level (4.16 kJ m(-2) UVB without PRR). Survival rates in the group that received PRR only and the group exposed to 2.08 kJ m(-2) and PRR were not significantly different from that in the control group; however, the survival rate was reduced for all other UVR exposures. We hypothesize that enhanced respiration rates reflect energetic costs related to repair of cellular components damaged by sublethal levels of UVR. Increases in respiration rate of the magnitude we found in our experiment could significantly reduce energetic reserves available for growth and reproduction, especially in cases where these costs are incurred repeatedly during a series of days with high levels of UVR.
我们研究了紫外线辐射（UVR）对淡水枝角类动物卡托巴水蚤代谢率的影响。我们将卡托巴水蚤置于灯控光反应箱中，使其暴露于2.08和4.16 kJ m(-2)水平的UVB下12小时，同时伴有或不伴有UVA和可见光光修复辐射（PRR）的暴露。我们还设置了仅接受PRR的组和黑暗对照组。暴露后测量6小时的呼吸速率。在最低UVB胁迫水平（2.08 kJ m(-2) UVB与PRR）下，呼吸速率相对于黑暗对照组增加了31.8%，而在最高胁迫水平（4.16 kJ m(-2) UVB无PRR）下，呼吸受到70.3%的抑制。仅接受PRR的组和暴露于2.08 kJ m(-2)及PRR的组的存活率与对照组无显著差异；然而，所有其他UVR暴露组的存活率均降低。我们推测，呼吸速率的提高反映了与修复由亚致死水平UVR损伤的细胞成分相关的能量消耗。我们在实验中发现的呼吸速率增加幅度可能会显著减少可用于生长和繁殖的能量储备，尤其是在一系列紫外线辐射水平较高的日子里反复产生这些消耗的情况下。
