The Losey Lab Research: Using UV
Dascyllus aruanus and Dascyllus reticulatus are two species of damselfish that live together in small branching coral heads on the Great Barrier Reef. As you can see in the pictures below, both species have very similar markings, and indeed, are hard to tell apart with our eyes. In the UV however, where both these fish can see, things are different. They may be distinguishing between species with the special UV-markings they display. These photos were taken from video shot with our ultraviolet videocamera system in 40 feet of water at Mermaid Cove on Lizard Island, Great Barrier Reef. We also got great footage of these little guys from the Quicksilver platform on Agincourt reef.
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These three frames were taken with the 400 nm filter, 360 nm filter, and 340 nm filter (L-R). A= D. aruanus, R= D. reticulatus. The bright area on D. aruanus at 400nm is likely due to downwelling light being 'bounced' off the fish, making it appear bright. This cannot be the case with the bright spot on reticulatus at 340nm, however, as the bright spot you see is on the vertical surface of the dorsal fin. The differences between the species may be due to the reflecting properties of the pigments which form the white areas in D. aruanus vs the pale yellow of D. reticulatus. Dascyllus aruanus may disappear at 340 due to the absorbing compounds found in its mucus. For more information on mucus absorption, look at our coping with UV pages.