Nudibranch Mimics Soft Coral

Xenia soft coral mimic nudibranch Anna DeLoach
Video frame capture of Phyllodesmium rudmani nudibranch

November 2012 ~ Blennywatcher is still on the road and delighted to report that we’ve managed to add quite a few species to our life lists during this cruise around Batanta, Indonesia, including this nudibranch, Rudman’s Phyllodesmium (Phyllodesmium rudmani). Nudibranchs are sea slugs, shell-less marine snails; a group that includes some of the most colorful and beautiful invertebrates on the reef. This is one that we’ve long wanted to see. Our guide, Yan Alfian seemed pretty confident that we’d see one on a night dive and indeed, found one for me within 60 seconds of descending into the shallows. Here is another amazing example of mimicry: the nudibranch mimics the Xenia soft coral upon which it feeds. Its mimicry is so good that its two white rhinophores, the sensory tentacles, are about the only way to distinguish it from the coral.

Click here to see a short video from our Blenny Watcher YouTube channel or watch it at the end of this post. One of the problems I have diving at night is the plankton I attract with my video lights – I’m a moving cloud of worms and other zooplankton. I spend a lot of time hovering in the dark, waiting for them to disperse, only to find my subject has moved or worse, disappeared! I kept my lights on so I wouldn’t lose this cryptic creature so you’ll see in the video why I have so few dive buddies at night.

Phyllodesmium rudmani nudibranch Anna DeLoach
Head on: it looks more like a nudibranch (video frame capture)