Understanding the mechanistic bases of marine clocks and rhythms in the Antarctic key species Euphausia superba

地球上几乎所有的生物都表现出每日和季节性的节律。这些节律是由内源性时钟产生的，这使得生物体，包括人类，能够将日常和季节性的生命周期功能与其环境的节律变化同步。相比之下，我们对海洋生物的内源性时钟以及它们如何与环境周期相互作用知之甚少。对于海洋生态的关键物种，如南极磷虾（Euphausia superba）来说尤其如此，南极磷虾是南大洋特有的，南大洋是一个高纬度地区，其特点是不同季节的极端环境变化（日照长度、光照强度、食物供应）。这些极地地区正在经历地球上最快的变暖，环境改变和生态系统的转变，导致营养相互作用和营养/能量通量的深刻变化。这些经过数百万年演变的精细调整的相互作用可能会因这些地区的快速气候变化而异相。因此，我们的首要目标是确定规则的环境线索（日/夜周期，光周期）如何产生分子节奏振荡，使极地海洋生物，如南极磷虾，以预期其环境中的节奏变化，并相应地预先调整其生命周期功能。为了实现这一目标，我们的目标是进一步调查参与内源性时钟到中央生命周期功能在南极磷虾，通过使用季节性行为实验沿着与时钟和代谢标记基因的基因表达分析。此外，我们的目标是表征的位置和解剖的主昼夜节律钟在大脑中的E。木荷通过使用荧光原位杂交和免疫细胞化学研究，以了解分子和神经元的机制，内源性时钟的基础。最后，我们将通过实验来操纵生物钟，以揭示内源性节律和不断变化的环境在多大程度上决定了南极磷虾的行为和生理。因此，我们希望进一步深入了解磷虾适应极端环境条件的机制，以及其对南大洋生态系统持续变化的可塑性。

Virtually all living beings on our planet exhibit daily and seasonal rhythms. These rhythms are generated by endogenous clocks, which allow organisms, including humans to synchronize daily and seasonal life cycle functions with rhythmic changes of their environment However, our current molecular understanding of biological rhythms and clocks is mostly restricted to land model species. By contrast, we know very little about the endogenous clocks of marine organisms, and how they interact with environmental cycles. This is particularly true for marine ecological keystone species like Antarctic krill (Euphausia superba), endemic to the Southern Ocean, a high latitude region which is characterized by extreme environmental changes across seasons (day length, light intensity, food availability). These polar regions are experiencing the fastest warming on the planet, with environmental alterations and ecosystem shifts, resulting in profound changes in trophic interactions and nutrient/energy fluxes. These finely tuned interactions, which have evolved over millions of years, are likely to going out of phase by the rapid climate change in these regions. Therefore, our overarching objective is to identify how regular environmental cues (day/night cycle, photoperiod) generate molecular rhythmic oscillations that allow polar marine organisms like Antarctic krill to anticipate the rhythmic changes in their environment, and to pre-adjust their life cycle functions accordingly. To achieve this, we aim to further investigate the involvement of endogenous clocks into central life cycle functions in Antarctic krill, by use of seasonal behavioural experiments along with gene expression analysis of clock and metabolic marker genes. In addition, we aim to characterize the location and anatomy of the master circadian clock in the brain of E. superba by use of fluorescent in-situ hybridization and immunocytochemical studies to understand the molecular and neuronal mechanisms that underly the endogenous clock. Finally, we will experimentally manipulate the circadian clock to reveal to which extent the endogenous rhythm and the changing environment determine the behavior and physiology of Antarctic krill. We thus hope to get further insights into the mechanisms that underly krill’s adaptation to extreme environmental conditions and into its plasticity towards ongoing changes in the Southern Ocean ecosystem.