Research breakthrough: Krill uses their internal clock for migrations that are essential for their survival!

Research breakthrough: Krill uses their internal clock for migrations that are essential for their survival!

The Antarctic krill (Euphausia superba) plays a crucial role in the marine ecosystem of the South Atlantic and is the primary food source for numerous predators. Up to 6 cm long and weighing approximately 2 g, these crustaceans are found in the waters surrounding Antarctica, including the Ross Sea, the Amundsen Sea and the Weddell Sea, to name a few. As part of a current study conducted by a research team at Julius Maximilian University of Würzburg The behavior of the krill was examined in more detail.

The study focused on “daily vertical migration in the water column.” It turned out that krill feed on the sea surface at night and retreat to deeper layers during the day to protect themselves from predators. Despite decades of research, the precise mechanisms of krill migratory behavior are not fully understood. To shed more light on this, the scientists used a new activity monitor that records the swimming activity of individual krill.

Krill internal clock

What was particularly surprising was that the results of the study showed how krill are able to adapt to the changing length of the nights. Even in constant darkness conditions, krill maintain a daily rhythm of activity. This suggests that krill have an internal clock that allows them to flexibly synchronize their behavior to the extreme lighting conditions in the polar regions.

The importance of this research extends far beyond the krill themselves. The Southern Ocean acts as a central carbon sink, and changes in krill populations can have serious impacts on the entire ecosystem. These findings were published in the publication “A circadian clock drives behavioral activity in Antarctic krill (Euphausia superba) and provides a potential mechanism for seasonal timing,” which appeared in the journal eLife at the end of April 2025.

Ecological significance and challenges

The biomass of Antarctic krill is estimated at around 500 million tonnes, making it one of the most successful species and an important part of the marine food chain. There can be up to 30,000 krill shrimp in one cubic meter of water. This high population density is crucial because a humpback whale can eat 5 to 7 tons of krill every day. However, krill are increasingly at risk of declining populations due to global warming and the loss of ice.

In addition to its ecological role, krill is also a popular frozen food for aquarium animals and is valued in the aquarium hobby. The krill-like organism also uses light pulses for communication and partner recognition, thereby supporting social behavior within its swarms. This multifaceted biology of krill shows the importance of ongoing research into their lifestyle and the impact that environmental changes can have on them.

In future projects, the researchers will Julius Maximilian University of Würzburg and other institutions continue to investigate krill's internal clock and its influence on reproduction and overwintering strategies. Antarctic krill therefore remains a central research topic that is not only of great interest to science, but also has far-reaching implications for the climate and the global ecosystem.