New to Science, Found in Singapore

Date January 23, 2021

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Phestilla fuscostriata by Nicholas Chew (2021)

By Nicholas Chew: I had seen some photos of an extremely cryptic nudibranch Phestilla viei by Chay Hoon over the last few months. It had superb camouflage, unlike anything I’d seen before. Mimicking the patterns and colours of the specific host coral Pavona explanulata, it blended in perfectly. I found it incredibly amazing and beautiful, and challenged myself to look for it whenever I was out diving.

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Photo of Phestilla viei by Toh Chay Hoon (2019) that inspired Nicholas Chew’s search.

The only clues to finding it are often the numerous crescent-shaped egg masses which it lays in bunches on the host coral. I then made it a habit to check almost every Pavona coral I came across for this amazing creature, but it just seemed to be so rare that I never encountered a single one up till now!

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The individual I found actually turned out to be a different species, Phestilla fuscostriata, which lives on the host coral Pavona decussata. At a glance, it is quite similar to Phestilla viei, but it has stripes on its body. Phestilla fuscostriata as well as Phestilla viei were only recently described in 2020, and are new to science.

The genus Phestilla currently has nine recognized species, among which, eight are obligate corallivores. Field observation and laboratory studies have revealed the specificity between Corals and their Nudibranch predators, with a particular species of Phestilla feeding on only one species or genus of Coral, which implies host shifts are associated with speciation.

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Finding it was really exciting for me, as I was not expecting it at all. My eyes just kind of drifted and landed on it, and then I went in for a closer look.

I will definitely try looking out for more such creatures in the future!

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