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Let me quote the description of Thordisa sanguinea in IPN at page 170:
"The reddish orange coloration with elongate papillae distinguish this species. The mid-dorsal papillae have opaque white markings."
Robert F. Bolland compiled from Baba (1955):
"The back is covered everywhere with thick-set pointed papillae which are apt to be developed into distinct filaments at their extremities. The general ground color above is a bright orange-yellow, with 3-4, dark, ocellar markings in the middle line. The dorsal papillae are whitish, the gills and rhinophores are dark brown, and the underside of the body is more pale than is the dorsum. [Baba's description was based on a 13mm animal]." The picture of the original drawings is from his OKINAWA SLUG SITE
The IPN description does not mention the 3-4 dark mid-dorsal markings, which are present at the picture.
Thordisa cf. sanguinea is characterized by its bright orange-red colour, and by the elongate translucent papillae. The rhinophores are brownish and have translucent white tips. The gills are translucent brownish-grey It differs from Thordisa sanguinea by the lack of opaque white mid-dorsal papillae, and by the lack of 3-4 dark mid-dorsal markings.
There are some pictures of Thordisa sanguinea at umiushi-zukan.com, some of them lack the opaque white mid-dorsal papillae, others lack the dark mid-dorsal markings, watching these variations, I guess the specimens #1 and #2might turn out to be a colour variants, for now I keep them seperate.
Dr. Alicia Hermosillo-González labelled it: Dorido rojo fuzzy.JPG
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs. Sea Challengers Natural History Books.
How to cite:
Köhler, E. (2016), published 8 February 2016, Thordisa cf. sanguinea Baba, 1955
available from http://www.Philippine-Sea-Slugs.com/Nudibranchia/Euctenidiacea/Thordisa_sanguinea_cf.htm