Known only from Hong Kong
Tso Wo Hang, Hong Kong. South China Sea. Depth: intertidal. April 1986.
Photo: Kathe Jensen
The body is transparent with some light brown pigmentation scattered over the dorsum and the cerata. There is a thin dark brown stripe along the anterior surface of the rhinophores which continues forward along the edge of the head on each side. There is a white stripe along the posterior surface of the rhinophores corresponding to the underlying mucous glands. There are numerous red spots scattered all over the body. The cerata are transparent but fine green tubules of the digestive gland are visible in them. The outer side of the cerata and the upper half of the inside of each ceras appears dark green from a close concentration of green digestive gland tubules.
Costasiella pallida rarely exceed 10 mm in length and feeds on the green alga Vaucheria vipera.
Jensen, K.R. (1985) Annotated checklist of Hong Kong Ascoglossa (Mollusca: Opisthobranchia), with descriptions of four new species. In: Proceedings of the 2nd International Workshop on the Malacofauna of Hong Kong and Southern China, Hong Kong, 1983. (Eds: Morton, B; Dudgeon, D) Hong Kong University Press, Hong Kong, 77-107.
Jensen, K.R. 1990. Three new species of Ascoglossa (Mollusca, Opisthobranchia) from Hong Kong, and a description of the internal anatomy of Costasiella pallida Jensen, 1985. In: The Marine Flora and Fauna of Hong Kong and Southern China (B. Morton, ed.), pp. 419-432. Hong Kong University Press.
Jensen, K.R. (1990) Feeding Behaviour of some Hong Kong Ascoglossa (Mollusca: Opisthobranchia). In: Proceedings of the Second International Marine biological workshop: The marine Flora and Fauna of Hong Kong and Southern China, Hong Kong, 1986. (Ed: Morton, B) Hong Kong University Press, Hong Kong, 961-978.
Rudman, W.B., 2005 (February 16) Costasiella pallida Jensen, 1985. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/costpall