November 1, 1999
From: Atsushi Ono
The three individuals in the attached photos are maybe the same species, but I hope you can check them for me.
UPPER RIGHT: I think this is a juvenile, 5mm long, at 5m depth. This was found underside of dead coral. Its body color is dark pink, tip of head shield is white.
LOWER LEFT: This is 15-20mm long, at 3m depth, I have seen 3 individuals. This body color is dark brown, tip of head shield is white little. This has two round light patches on its head shield. I show this in my book.
LOWER RIGHT: This is similar to P. smaragdinus. Body color is dark green, 20mm long, at 3m depth.
Ono, A., 1999 (Nov 1) Phanerophthalmus from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1468
I suspect that Phanerophthalmus gets some of its body colour from the algae it is feeding on, which could explain some of the colour variation from pink to dark green. I am not sure though about the black forms. The white edging at the posterior tip of the headshield in both pink and black animals does suggest they are the same species. I have seen small pink animals and larger ones ranging from a translucent pale green to a dark greenish-black but never pure black ones like the one in your photo.
The only way to be sure if they are the same species is to have a look their anatomy to see if we can find any differences in the shape of their teeth or gizzard plates.
Colour variation in Phanerophthalmus from Reunion.
From: Hugues Flodrops, October 12, 2007
Another grass bed find from the Philippines
From: Charles Raabe, July 10, 2006
Phanerophthalmus smaragdinus from Reunion Island
From: Philibert Bidgrain, February 23, 2006