Humberg Tim-Henning, Sprecher Simon G
Department of Biology, University of FribourgFribourg, Switzerland.
Front Behav Neurosci. 2017 Apr 20;11:66. doi: 10.3389/fnbeh.2017.00066. eCollection 2017.
Animals use various environmental cues as key determinant for their behavioral decisions. Visual systems are hereby responsible to translate light-dependent stimuli into neuronal encoded information. Even though the larval eyes of the fruit fly are comparably simple, they comprise two types of photoreceptor neurons (PRs), defined by different Rhodopsin genes expressed. Recent findings support that for light avoidance Rhodopsin5 (Rh5) expressing photoreceptors are crucial, while Rhodopsin6 (Rh6) expressing photoreceptors are dispensable under laboratory conditions. However, it remains debated how animals change light preference during larval live. We show that larval negative phototaxis is age-independent as it persists in larvae from foraging to wandering developmental stages. Moreover, if spectrally different Rhodopsins are employed for the detection of different wavelength of light remains unexplored. We found that negative phototaxis can be elicit by light with wavelengths ranging from ultraviolet (UV) to green. This behavior is uniquely mediated by Rh5 expressing photoreceptors, and therefore suggest that this photoreceptor-type is able to perceive UV up to green light. In contrast to laboratory our field experiments revealed that larvae uses both types of photoreceptors under natural lighting conditions. All our results, demonstrate that larval eyes mediate avoidance of light stimuli with a wide, ecological relevant range of quantity (intensities) and quality (wavelengths). Thus, the two photoreceptor-types appear more likely to play a role in different aspects of phototaxis under natural lighting conditions, rather than color discrimination.
动物利用各种环境线索作为其行为决策的关键决定因素。视觉系统在此负责将光依赖型刺激转化为神经元编码信息。尽管果蝇的幼虫眼睛相对简单，但它们包含两种类型的光感受器神经元（PRs），由所表达的不同视紫红质基因定义。最近的研究结果支持，对于避光而言，表达视紫红质5（Rh5）的光感受器至关重要，而在实验室条件下，表达视紫红质6（Rh6）的光感受器则是可有可无的。然而，动物在幼虫期如何改变对光的偏好仍存在争议。我们发现幼虫的负趋光性与年龄无关，因为它在从觅食到化蛹前发育阶段的幼虫中都持续存在。此外，是否使用光谱不同的视紫红质来检测不同波长的光仍未得到探索。我们发现，波长范围从紫外线（UV）到绿光的光都能引发负趋光性。这种行为由表达Rh5的光感受器独特介导，因此表明这种光感受器类型能够感知从紫外线到绿光的光。与实验室情况不同，我们的野外实验表明，在自然光照条件下，幼虫会使用两种类型的光感受器。我们所有的结果表明，幼虫眼睛介导了对具有广泛生态相关数量（强度）和质量（波长）的光刺激的回避。因此，这两种光感受器类型似乎更有可能在自然光照条件下趋光性的不同方面发挥作用，而不是在颜色辨别方面。
