Fleissner Gerta, Schuchardt Kirsten, Neumann Dietrich, Bali Geetha, Falkenberg Gerald, Fleissner Guenther
Institut für Zellbiologie and Neurowissenschaften, J W Goethe-Universität Frankfurt a M, Frankfurt a M, Germany.
Chronobiol Int. 2008 Feb;25(1):17-30. doi: 10.1080/07420520801904008.
Living in the tidal zones of the sea requires synchronization with the dominant environmental influences of tidal, solar, and lunar periodicity. Endogenous clocks anticipate those geoclimatic changes and control the respective rhythms of vital functions. But the underlying mechanisms are only partly understood. While the circadian clocks in animals are investigated employing neurobiological, molecular, and genetic approaches, clocks with a lunar periodicity have been studied with reference to development and behavior only. Sites of their pacemakers, zeitgeber receptors, and coupled endocrine components are unknown. Here, a lunar-rhythmic change of shielding pigment transparency in the larval ocelli of the intertidal midge Clunio marinus is demonstrated for the first time as a possible access to the neurobiology of lunar timing mechanisms. We studied third instar larvae (Vigo strain) throughout the lunar cycle by light- and electron-microscopy as well as by x-ray fluorescence analysis for the identification of the pigment. Moonlight detection is a prerequisite for photic synchronization of the lunar clock. The larval ocelli of Clunio putatively may function as moonlight receptors and are also controlled by the circalunar clock itself, hence being primary candidates for tracing input and output pathways of the lunar pacemaker. Additionally, the demonstration of a reversible optical change of shielding pigment transparency in Clunio is a novel finding, not reported so far in any other animal species, and reveals a mechanism to enhance photosensitivity under the condition of very dim light. It represents a remarkable change of a sense organ from an imaging device to a radiometer. Its restriction to the developmental stage susceptible to lunar timing elucidates a unique sensory strategy evolved at the level of sensory input. It also raises basic questions about the biochemistry of optically active pigments, like melanin, and their intracellular control.
生活在海洋潮间带需要与潮汐、太阳和月球周期性等主要环境影响保持同步。内源性时钟能预测这些地球气候的变化，并控制重要功能的相应节律。但其潜在机制仅被部分理解。虽然动物的昼夜节律时钟是通过神经生物学、分子和遗传学方法进行研究的，但具有月球周期性的时钟仅在发育和行为方面得到了研究。其起搏器、授时因子受体和相关内分泌成分的位置尚不清楚。在此，首次证明潮间带蠓虫海栖克洛纽虫幼虫单眼的屏蔽色素透明度存在月节律变化，这可能是了解月球计时机制神经生物学的一个切入点。我们通过光学显微镜和电子显微镜以及X射线荧光分析，对整个月周期的三龄幼虫（维哥菌株）进行了研究，以鉴定色素。月光检测是月球时钟光同步的先决条件。海栖克洛纽虫幼虫的单眼可能作为月光受体，并且也受太阴时钟本身的控制，因此是追踪月球起搏器输入和输出途径的主要候选对象。此外，海栖克洛纽虫屏蔽色素透明度存在可逆光学变化这一发现是新颖的，迄今为止在任何其他动物物种中都未报道过，它揭示了一种在极暗光条件下增强光敏感性的机制。这代表了一种感觉器官从成像装置到辐射计的显著变化。其仅限于对月球计时敏感的发育阶段，阐明了在感觉输入层面进化出的一种独特的感觉策略。这也引发了关于光学活性色素（如黑色素）的生物化学及其细胞内控制的基本问题。
