Natural light is thought to be one of essential environmental factors dictating the ways animals live their lives. In aquatic animals, like coral larvae, the intensity and color of the light can be a crucial factor associated with swimming and moving behavior.

A new research study by a team of Japanese researchers, published in Scientific Reports, has explained how Acropora tenuis (a common reef coral) larvae move through the deep sea in response to the light intensity and color. 

Coral larvae are the free-moving life stage of corals, and they build colonies of the things that we think of as reef corals. The researchers found that these coral larvae swim slower in deeper water where there is less light, and that blue light is a particularly important cue for swimming. This is remarkable, since larvae lack eyes, yet they can still sense light intensity and color. The researchers suggest that this behavior could help the larvae locate habitat with the bright and blue wavelengths of light they need as adults. 

This behavioral phenomenon in coral larvae provides a more fundamental understanding of the early phases of larval settlement coral reefs in the natural environment.