Dietary Photoprotective Compounds Ameliorate UV Tolerance in Shrimp (Pleoticus muelleri) through Induction of Antioxidant Activity

The aim of this study was to determine the effects of ultraviolet radiation (UVR) on bioaccumulation of UV‐absorbing compounds acquired through the diet, in larvae and postlarvae of Pleoticus muelleri, and to assess tissue antioxidant activity, survival, and development. Mysis stage I were exposed to two artificial radiation treatments: M‐PAR (photosynthetically active radiation, range = 400–700 nm) and M‐PAR + UVR (280–700 nm). The experimental larvae received a mixed dietary treatment of Artemia persimilis and the microalga Pavlova lutheri, reared under two radiation regimes: PAR (D‐PAR) and PAR + UVR (D‐PAR + UVR). Shrimp from all treatments reached 8 d postlarval stage (PL8), except those under M‐PAR + UVR treatment fed the D‐PAR‐cultured algae, which had 0% survival. Larvae in M‐PAR + UVR and M‐PAR treatments fed with D‐PAR + UVR diet presented the highest survival rates (70 and 75%, respectively), with 37 and 41% increase in PL size. UV‐absorbing compounds were detected in microalgae and PL subject to PAR + UVR treatments. Antioxidant activity, quantified by measuring the free‐radical 1,1‐diphenyl‐2‐picrylhydrazyl in homogenates of PL8, decayed drastically under radiation treatment M‐PAR + UVR fed with algae of the D‐PAR + UVR treatment. It is concluded that the bioaccumulation of UV‐absorbing compounds and the highest antioxidant activity in PL could improve the biochemical and photophysiological responses of shrimp under UVR stress.     

阳光紫外辐射对2种微藻的短期影响

为了阐明2种赤潮藻柔弱角毛藻(Chaetoceros debilis)和绿色巴夫藻(Pavlova viridis)对阳光紫外辐射(UVR, 280～400 nm)变化的响应,比较研究了它们在全波段阳光下和滤除UVR/UV-B条件下的有效光化学效率变化,同时探讨了室内无UVR的低光条件下其有效光化学效率的恢复。结果表明,阳光UVR抑制藻细胞的有效光化学效率,其抑制程度随着接受辐射处理时间的延长而增大,在10 min左右细胞内的修复与损伤速率达到平衡,抑制率不变,且阳光UVR对二种藻的抑制程度相差不大。转移到无UVR的弱光条件下,藻细胞的有效光化学效率得到恢复,但恢复过程中柔弱角毛藻恢复明显快于绿色巴夫藻,体现了不同藻细胞对阳光UVR响应的种间差异。     

紫外辐射对条斑紫菜不同部位藻体光化学效率和光合色素含量的影响

实验室条件下研究了紫外辐射(UVR)对条斑紫菜藻体不同部位最大光化学效率(Fv/Fm)和光合色素含量的影响,以探讨条斑紫菜不同部位对紫外辐射反应的差异性。在全光谱 PAB(PAR+UV-A+UV-B,280~700 nm)和滤除紫外辐射UVR(UV-A+UV-B)的有效光辐射(PAR,395~700 nm)两种处理下进行测定。实验结果表明,PAB处理后的各部位藻体最大光化学效率下降程度均高于PAR处理后,且弱光期恢复程度低、速度慢。藻体不同部位间最大光化学效率下降程度也存在差异,藻体梢部对PAB的耐受性高,恢复也较快;基部耐受性最差,恢复也较慢。藻红蛋白(phycoerythrin,PE)和藻蓝蛋白(phycocyanin,PC)对不同辐射处理较敏感,PAB辐射处理后,各藻体部位的PE、PC含量均显著上升(P<0.05),其中藻体梢部PAB处理后的PE、PC含量的均极显著升高(P<0.01)。然而不同部位藻体在PAB和PAR照射下,叶绿素a(Chl.a)和类胡萝卜素(Car)并无显著变化(P>0.05)。藻体的紫外吸收物质(MAAs)的含量从基部到梢部逐步升高,不同辐射处理前后,各藻体部位的紫外吸收物质也未显著增加(P>0.05)。总之,条斑紫菜不同部位藻体光合生理特性存在较大差异。推测条斑紫菜应对紫外辐射的策略有遮蔽作用,积累紫外吸收物质和动态光抑制作用。     

汕头南澳岛沿岸浮游植物对阳光紫外辐射响应的研究

为了阐明汕头南澳岛沿岸表层水体浮游植物群落对阳光紫外辐射(UVR,280～400nm)变化的响应,试验检测了浮游植物在全波段阳光和滤除UVR或UV-B条件下的光合固酸随光强的变化关系,同时还检测了浮游植物群落的紫外辐射作用光谱(BWF).结果表明,阳光UVR可以明显的抑制浮游植物的光合固碳,当滤除UVR后,光合固碳受到的抑制程度下降.在100％阳光辐射条件下,光合固碳受到的抑制程度最大.紫外辐射作用光谱显示,浮游植物对UV-B最敏感,其抑制程度显著大于UV-A波段.     

The impact of solar ultraviolet radiation on fish: Immunomodulation and photoprotective strategies

One of the many environmental factors affecting the health of both farmed and wild fish is exposure to solar ultraviolet radiation (UVR). These rays penetrate to biologically relevant depths in natural waters and cause changes ranging from embryo malfunction to the production of heat‐shock proteins. As suppression of cell‐mediated immunity has been shown to follow irradiation of mammals, the possibility of UVR‐induced modulation in immune responses in fish is considered in this review. It is suggested that, after adsorption of UV photons by surface chromophores, dendritic‐like cells may be activated by immune mediators, leading to the generation of T‐ and B‐cell subsets with down‐regulatory activity. A limited number of studies involving infection of irradiated fish with bacteria, nematodes and protozoa have demonstrated an increased microbial load and lack of clearance, with associated changes in a variety of immune parameters. These preliminary results indicate that exposure of fish to solar UVR leads to less effective control of infections. Strategies evolved by fish to avoid overexposure to UVR include photoenzymatic repair, nucleotide excision repair, pigments, mycosporine‐like amino acids and habitat selection. The welfare of farmed fish is of concern currently. The detrimental effects of excessive sun exposure on the health of fish require recognition, and procedures put in place to minimize such consequences.