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的节律。这些节律是由内源性时钟产生的，内源性时钟允许包括人类在内的生物体将日常和季节性生命周期功能与其环境的节律变化同步。然而，我们目前对生物节律和时钟的分子理解主要局限于陆地模式物种。相比之下，我们对海洋生物的内源性生物钟以及它们如何与环境周期相互作用知之甚少。对于南极磷虾(Euphausia Superba)等海洋生态关键物种来说尤其如此，这种物种是南大洋特有的，是一个高纬度地区，其特点是不同季节(日长、光照强度、食物可获得性)发生极端的环境变化。随着环境变化和生态系统变化，这些极地地区正在经历地球上最快的变暖，导致营养相互作用和营养/能量通量发生深刻变化。这些微调的相互作用经过数百万年的演变，很可能会随着这些地区的快速气候变化而不同步。因此，我们的首要目标是确定常规环境信号(昼夜周期、光周期)如何产生分子节奏振荡，使南极磷虾等极地海洋生物能够预测其环境的节奏变化，并相应地预先调整它们的生命周期功能。为了实现这一目标，我们的目标是通过季节性行为实验以及时钟和代谢标记基因的基因表达分析，进一步研究内源时钟参与南极磷虾的中心生活周期功能。此外，我们的目标是通过荧光原位杂交和免疫细胞化学研究来表征大闸蟹脑内主生物钟的位置和解剖结构，以了解内源性生物钟背后的分子和神经机制。最后，我们将通过实验操作生物钟来揭示内源节奏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，以及磷虾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.