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Reef Fish Talk in UV

Researchers at The University of Western Australia have examined when and under what conditions juvenile damselfish develop ultraviolet facial patterns to communicate vital information to each other while remaining undetected by potential predators.

A/Prof Monica Gagliano said the study found that young fish are unable to develop the UV facial patterns unless they are surrounded by their natural environment. “These baby fish are under tremendous pressure from predators so their first ‘words’ are most likely going to be important ones, ones that enhance survival,” she said.

“Consequently, we expected that all fish would develop these UV markings at a young age and that their development was “hard-wired”, but to our surprise we found that the markings only developed when fish were exposed to their natural environment on the reef.”

Dr Martial Depczynski of the Australian Institute of Marine Science said that the study, published in Scientific Reports, put lab-based fish under a whole range of different feeding and social conditions to exclude everything else that was important to young fish at this critical stage of their lives. “The next obvious study is to see if exposure to predators in a lab-based environment is enough to trigger the markings,” he said.

“Understanding what and how much animals are able to communicate to each other is one of science’s most intriguing mysteries,” Gagliano added. “Because there are so many predators on a coral reef and life is so risky for baby fish, the ability to communicate danger is the most likely explanation for the absence of UV markings in our lab experiments and why they develop them so quickly on the reef.”

Gagliano said that the research has major implications for our understanding of the role of structural colouration in animals. “Traditionally, UV colour has been studied in the context of mate selection, but these fish are not only sexually immature, they are also all born female, suggesting that these colours have a different function at this early stage in life, one that may change as fish get older.

“Regardless, it seems that UV signalling may convey a whole range of different information, and we are just touching the tip of the iceberg with this research.”