Japan, from central Honshu to southern Hokkaido.
Closeup of head on left showing 4 lines which give the species its name. PHOTO: Yoshi Hirano.
Facelina quadrilineata is one of the commonest glaucid nudibranchs in Japan and is known from central Honshu to southern Hokkaido. It is characterised by the 4 lines on its head. Baba (1935) recognised a variety, with a slightly different colour variety which has recently been separated as a distinct species, Facelina bilineata. Apart from slight colour differences, there are significant differences in egg size and development, and the penial anatomy. In Facelina quadrilineata the vas deferens opens at the base of the penial papilla while in Facelina bilineata it runs through the papilla to open at the tip.
• Ito, M. & Hirano, Y. (1996) the spawn and embryonic development of two colour morphs of the aeolid nudibranch Facelinella quadrilineata(Baba, 1930). Venus, 55(2): 115-121.
• Hirano, Y.J. & Ito, M. (1998). 'Facelinella quadrilineata' (Baba, 1930), a pair of cryptic species of Facelina from Japan. Zoological Science, 15: 791-797.
Rudman, W.B., 1999 (June 26) Facelina quadrilineata (Baba, 1930). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/facequad