Biological clocks are found in almost all life forms, from bacteria to humans, and enable organisms to anticipate environmental cycles and regulate their behaviour and physiology accordingly. While the mechanistic principles of these endogenous timing mechanisms have been extensively studied in terrestrial model species (e.g. fruit fly or mouse), little is known in the marine environment, where life – and with it biological clocks – have evolved. Antarctic krill (Euphausia superba) is a key species, endemic to the Southern Ocean which is a high latitude region characterized by extreme seasonal fluctuations in environmental factors (photoperiod, sea ice extent, food availability). The life cycle of Antarctic krill is shaped by strong diel rhythms (DVM, metabolic activity), synchronized to the day-night cycle, and seasonal rhythms (growth, lipid accumulation, gene expression), synchronized to the seasonal change in photoperiod and food availability, making Antarctic krill highly adapted to a life under extreme conditions. Recent investigations suggest the involvement of an endogenous clock into both diel (DVM, metabolic activity) and seasonal (e.g. growth, enzyme activity and gene expression) processes. Moreover, in a transcriptomic study the molecular components of an endogenous clock have been characterized in E. superba. However, so far nothing is known about the underlying mechanistic principles and the neuronal architecture of this clock and how it is synchronized to the environment – key to understand diel and seasonal timing in Antarctic krill. With parts of the Southern Ocean experiencing rapid warming caused by anthropogenic driven climate change, it is of fundamental interest to understand the involvement of endogenous timing mechanisms into life cycle functions of Antarctic krill to get insights into its plasticity towards environmental change. These information are essential for model studies about krill’s population development in the future in relation to environmental changes caused by the anthropogenic warming.
Central research question: How does the involvement of the biological clock into life cycle functions of Antarctic Krill influence its plasticity towards climate change?
Objective 1: Investigate the impact of the endogenous clock in life cycle functions and their seasonal adaptations in Antarctic krill caught in the field
Objective 2: Characterize the neuronal mechanisms underlying rhythmic behaviour in Antarctic krill.
To understand how the involvement of the endogenous clock in life cycle functions of Antarctic Krill influence its plasticity towards environmental changes, the MEMAREs project combines seasonal field samplings and molecular biological methods with laboratory experiments (behaviour, metabolic activity) and field observations (acoustics).
The basis of this project are the seasonal sampling campaigns in the Southern Ocean onboard the krill fishery vessel “Antarctic Endurance”. This vessel is equipped with a novel vacuum pump system to catch krill in a gentle way and is therefore ideally suited as a platform to perform chronobiological time series samplings as well as behavioural and metabolic experiments with living krill on board.
On these field campaigns we will for the first time use a novel behavioural screening system for krill, which we developed at the Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research (AWI). This set up is based on a compressor cooled incubator which will ensure stable in-situ temperatures throughout the experiment and which is equipped with 12 so called DVM columns. Each of these columns is fitted with infra-red light barriers which detect krill vertical movements throughout the column. The detections are recorded on small single board computers attached to each column and the data can be accessed in real time without disturbing the experiment. Programmable LED light bars at the ceiling of the incubator allow to control the light spectrum and intensity and enable us to perform behavioural experiments under different light conditions. In parallel to the onboard behavioural experiments we will observe the krill behaviour in the field using the ships acoustic instruments.
In addition, we will also perform onboard oxygen consumption experiments under different light conditions and aim to characterize the underwater light climate (spectrum, irradiance) in the krill habitat using a hyperspectral light sensor.
Samples obtained from seasonal time series samplings in the field will be used subsequently in various molecular biological methods to investigate seasonal clock gene expression patterns (using quantitative real-time PCR) and to characterize the location and anatomy of the master circadian clock in the brain of Antarctic krill (using single molecule Fluorescent In Situ Hybridization and Fluorescent immunocytochemistry).
The project is funded by the priority program “1158 – Antarctic Research with Comparative Investigations in Arctic Ice Areas” of the German Science Foundation (DFG)