Costasiella ocellifera
(Simroth, 1895)

Family: Costasiellidae




Lark Cay, Belize. Photo: Jeff Hamann

Body translucent clear, covered with black spots. The head can have orange yellow patches, and the large black eyes, close together between the rhinophores are very prominent. The rhinophores are long and tapering with the black spots increasing in density so that the upper half is almost black. Behind the rhinophores, in the midline is a characteristic blue spot, which is bordered with a thin line of black, brown or orange. The name 'ocellifera' refers to this ringed blue spot. The inflated cerata narrow to a long thin tapering tip. The ceratal wall is transparent with black spots, and the ceratal digestive gland ducts are green from being filled with green chloroplasts. There can be scattered bluish-white patches on the ceratal wall, and there is a subapical orange yellow band around the cerata, just down from the tip. The black spots become more crowded near the tip. This species was originally described from Bermuda as Doto ocellifera. Clark (1984) redescribed this species from Bermuda and reported that it was common on Avrainvillea. Redfern (2001) reports that it is also common in the Bahamas.

Clark (1984) proposes that Costasiella lilianae (Marcus & Marcus, 1969), originally described from Brasil, is a synonym. I do not know if it is important, but in the colour description of C. lilianae I can see no mention of the blue spot behind the rhinophores. Other aspects of the colour pattern are identical.

• Clark, K.B. (1984) New records and synonymies of Bermuda opisthobranchs (Gastropoda). The Nautilus, 98(2): 85-97.
• Marcus, Ev. & Marcus, Er. (1969) Euthyneure Meeresschnecken Brasiliens. (2). Beitrage zur Neotropischen Fauna, 6(1): 1-16.
• Miles, C.M. & Clark, K.B. (2002) Comparison of biochemical composition and developmental mode in two populations of Costasiella [Opisthobranchia: Ascoglossa (=Sacoglossa)]. Journal of Molluscan Studies, 68: 101-109.
• Redfern. C., 2001. Bahamian Seashells: a Thousand Species from Abaco, Bahamas
• Simroth, H., 1895. Opisthobranchia Gymnobranchia.Die Gastropoden der Plankton Expedition, 2: 1-206

Authorship details
Rudman, W.B., 2002 (October 8) Costasiella ocellifera (Simroth, 1895). [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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