Winckler K, Fidhiany L
Institut für Biophysik AG Strahlenbiologie, Freie Universität Berlin.
Z Ernahrungswiss. 1998;37 Suppl 1:80-4.
In the tropics organisms have permanently adapted to deal with extremely high intensities of light, temperature and other environmental factors. Especially in coastal environments and fish farmings conditions can easily reach and exceed the tolerance limits of an organism. The UV-A band has been shown to be a potent modulator of light induced effects and general physiological functions in organisms. The biological endpoints and underlying mechanisms still have to be investigated. Our experiments were carried out with the easy to handle sub-tropical Convict-Cichlid fish (Cichlasoma nigrofasciatum) as a model organism. In our studies we observed that constant sub-lethal UV-A irradiation had a significant effect on the general metabolism and on the sensitivity towards other environmental stress factors in this fish. We found that, in addition to the depression of the general metabolism, sub-lethal UV-A irradiation in combination with elevated environmental temperature had a deleterious effect on the population. The threshold temperature for a sudden increase in mortality of the fish receiving the additional sub-lethal UV-A irradiation was 32 degree C. The fish were grown and adapted at 27-29 degrees C. A total of 78% of the fish receiving an additional UV-A irradiation died by high temperature stress while the reference population remained at a normal level (3%). The metabolic rate (MR) of the UV-A survivors during temperature stress was less than half the average value obtained in the reference population. After the environmental temperature returned below the apparent upper tolerance limit for this fish, the MR of UV-A population gradually increased to normal. Apparently a constant elevated sub-lethal dose of UV-A leads to the destabilization of an organism, making it more sensitive for other environmental stress factors. These observations seem to be important considerations in fish farming in the tropical and subtropical regions.
在热带地区，生物已经永久适应了应对极高强度的光照、温度和其他环境因素。特别是在沿海环境和养鱼场环境中，条件很容易达到并超过生物的耐受极限。UV-A波段已被证明是生物体内光诱导效应和一般生理功能的有力调节因子。其生物学终点和潜在机制仍有待研究。我们的实验以易于处理的亚热带 convict-cichlid 鱼（黑带丽体鱼）作为模式生物进行。在我们的研究中，我们观察到持续的亚致死剂量UV-A照射对这种鱼的一般新陈代谢以及对其他环境应激因素的敏感性有显著影响。我们发现，除了一般新陈代谢的抑制外，亚致死剂量的UV-A照射与环境温度升高相结合对鱼群有有害影响。接受额外亚致死剂量UV-A照射的鱼死亡率突然增加的阈值温度为32摄氏度。这些鱼在27 - 29摄氏度下生长和适应。接受额外UV-A照射的鱼中，共有78%因高温应激死亡，而对照鱼群仍保持在正常水平（3%）。UV-A存活鱼在温度应激期间的代谢率（MR）不到对照鱼群平均值的一半。当环境温度降至这种鱼明显的上限耐受极限以下后，UV-A鱼群的MR逐渐恢复正常。显然，持续升高的亚致死剂量UV-A会导致生物体内平衡的破坏，使其对其他环境应激因素更加敏感。这些观察结果似乎是热带和亚热带地区养鱼业的重要考虑因素。
