Krill, reproduction, and daylight

The Australian Antarctic Division released the results of research demonstrating that light exposure plays a critical role in determining when krill spawn. During the Antarctic winter (June to September), krill are in darkness, and they are unable to reproduce. A few months after winter ends and light returns, they spawn again. It was previously thought that internal cues govern this process, since some experiments showed that krill kept in total darkness or light had the same reproductive cycle as those that lived under a more natural cycle. But this new research indicates that it is a change in light conditions that governs their reproduction. According to the press release:

The third group of krill experienced one month of the natural Antarctic light cycle, followed by two months of darkness, and nine months of light (the 'light 1' treatment). These krill reached sexual maturity three months earlier than the other groups – observed by changes in their exoskeleton (shell), which they shed as they grow.

'This study has shown that the transition from light to dark to light is important in controlling the timing of spawning under laboratory conditions,' Dr Kawaguchi says.

This kind of research is very important as it adds to our understanding of the krill life cycle. Although krill are the subject of many research projects, we still don't know a lot about them, and the gaps in knowledge may complicate efforts to ensure a balance between commercial fishing and the needs of the Antarctic ecosystem.