Phyllodesmium kabiranum from Palawan, Philippines

February 17, 2007
From: Michael Jimenez

Hi Bill,

I found this Phyllodesmium kabiranum on my last dive off the southern island of Palawan in the Philippines. Sorry for the quality. It was underneath a large table coral and I had to maneuver my camera and strobe through a maze of staghorns to get to it. Being towards the tail-end of the dive, I wasn't able to fire off many shots. It's a very interesting slug and I noticed that this particular one is more "blue" in color than the ones posted. I wonder why?

Locality:  Isla Blanca, Depth: 50 ft, Palawan, Philippines. Sulu Sea, Length: 3 inches. 1 April 2005. Reef dominated by table and staghorn corals. Photographer: Michael Jimenez

Mike

mpj17@pacbell.net

Jimenez, M., 2007 (Feb 17) Phyllodesmium kabiranum from Palawan, Philippines. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13553

Dear Mike,

These milky blue colours are often structural colours rather than pigment colours -that is the difference between the colour of paint on your house and the colours produced by light on an opal or diamond. I am not sure if that is the case here, but in Pteraeolidia ianthina, the darker brown the background colour is, the more noticeable is the blue colouration on the animal. Interestingly, Pteraeolidia is a solar-powered slug, and the darkness of the brown in its body is a measure of the number of the single-celled plants [zooxanthellae] it has in its tissues. For some reason the white surface pigments seem to reflect blue light better if there is a dark layer beneath them. Interestingly. P. kabiranum also harbours photosynthetic zooxanthellae.  Perhaps Ingo Burghardt, or one of the other researchers at present working on these fascinating zooxanthellae symbioses, can 'throw some light' on this.

At the top of your photo there are some similar coloured anemone-like polyps of the xeniid soft coral (Xenia or Heteroxenia), which your Phyllodesmium was probably eating.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Feb 17). Comment on Phyllodesmium kabiranum from Palawan, Philippines by Michael Jimenez. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13553

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