Thuridilla undula
Gosliner, 1995

Order: SACOGLOSSA
Superfamily: ELYSIOIDEA
Family: Elysiidae

DISTRIBUTION

Papua New Guinea, Guam, Palau, the Philippines and the Maldives

PHOTO

near Honiara, Solomon Islands, 8m. June 2001. Photo: Bruce Potter.

Living animals are turquoise bluish green. The parapodial margin is a burnt orange colour. Below that is a narrow line of black followed by a region of vivid blue pigment. This black and blue pigment is also on the head and the mid region of the rhinophores. The tips of the rhinophores are orange while the base are the same turquoise blue-green of the body. Orange, black and blue bands are also present on the anterior margins of the foot. T. undula is similar in colour to T. neona Gosliner, 1995. Both have a turquoise body with burnt orange, black and blue undulating parapodial bands. However T. neona has additional bright orange markings on the parapodia, anterior margin of the foot and the rhinophores. In T. undula the orange, blue and black markings on the rhinophores are transverse bands, while in T. neona they are diagonal. T. undula is even closer in colour to T. lineolata (Bergh, 1905), the main difference being that the colour bands at the parapodial edge undulate in T. undula and are parallel to the edge in T. lineolata. Gosliner reports that the two species differ in the branching of the veins off the pericardium, highly branched in T. undula and only bifurcating in T. lineolata.

See Thuridilla coerulea for comparison with the similarly coloured T. undula and T. lineolata.

• Gosliner, T.M. (1995) The genus Thuridilla (Opisthobranchia: Elysiidae) from the tropical Indo-Pacific, with a revision of their phylogeny and systematics of the Elysiidae. Proceedings of the California Academy of Sciences, 49(1): 1-54.

Authorship details
Rudman, W.B., 2001 (June 9) Thuridilla undula Gosliner, 1995. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/thurundu

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