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**Summary:**

A recent study published in *eLife* reveals that Antarctic krill ( *Euphausia superba*) possess a robust circadian rhythm that persists even when exposed to constant darkness, mimicking conditions of disrupted day/night cycles. Researchers used a device called AMAZE to track the diel vertical migration (DVM) patterns of krill collected from the Southern Ocean. The study found that krill’s DVM, the daily movement between surface and deeper waters, is tied to the timing of daylight and darkness, rather than fixed hours, and this pattern continues even in the absence of light. This research provides insight into how krill, a keystone species in the Southern Ocean ecosystem, adapt to their environment and respond to environmental changes, especially in the face of a warming ocean.

**News Article:**

**Antarctic Krill Exhibit Unwavering Internal Clocks, Study Finds**

*By Science Correspondent*

**June 20, 2025 (The Hindu) -** A new study published in the journal *eLife* has revealed the remarkable resilience of Antarctic krill (*Euphausia superba*), tiny crustaceans that play a critical role in the Southern Ocean’s ecosystem. Researchers have discovered that these creatures possess a sophisticated internal clock, or circadian rhythm, that continues to operate even when exposed to prolonged darkness.

The study, conducted by researchers from Germany and the U.K., focused on diel vertical migration (DVM), the daily movement of krill between the surface and deeper waters of the ocean. Using a specially designed device called the Activity Monitor for Aquatic Zooplankter (AMAZE), scientists tracked the movement of krill under various light conditions, including continuous darkness.

“We know that krill move up and down in the water column each day which also has important implications on nutrient cycling and carbon sequestration, but we don’t know what mechanism governs this behaviour. This study sheds light on that, and will help us better understand and conserve this incredible species,” says Matthew Savoca, a research scientist at the Hopkins Marine Station of Stanford University and who wasn’t involved in the study.

The findings revealed that krill’s DVM patterns are linked to the timing of daylight and darkness, regardless of the actual time of day. More significantly, even in complete darkness, the krill maintained their DVM behavior, indicating a robust internal clock controlling their movements.

“The findings provide novel insights into the mechanistic underpinnings of daily and seasonal timing in Antarctic krill,” explained Lukas Hüppe, a doctoral researcher at the University of Würzburg in Germany and coauthor of the study.

The research has significant implications for understanding how krill, a crucial food source for numerous marine species including seals, penguins, and whales, adapt to their environment and respond to ongoing environmental changes, particularly the rapidly warming Southern Ocean. Understanding these mechanisms is crucial for conservation efforts in this sensitive ecosystem.

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