Southeastern Australia: from St. Vincent Gulf to northern New South Wales.
16 mm specimen, from the low intertidal, Bundeena, Port Hacking, New South Wales, 21 June 1980. Lower photo showing anal papilla. Photo: Richard Willan.
Besides the lack of a crest and pleated bulges on the bases of the rhinophores, the genus Caldukia has fewer cerata than Janolus so that they never completely obscure the back. Caldukia affinis grows to 20 mm. The cerata, which are flattened in cross section, possess a large brown “lumpy” (never forked) diverticulum off the digestive gland at its core. The cerata cannot be cast off (autotomised) when the animal is provoked. This zephyrinid is closest to Caldukia rubiginosa from New Zealand, but it differs consistently in colouration and in the shape of the radula teeth. C. affinis has a reddish brown back that is conspicuously speckled with pale brown and silvery patches. The diverticulum is relatively “fatter” in C. affinis that is, it occupies more of the space within each ceras, and the diverticulum itself is brown and marked with a network of white lines. C. rubiginosa does not have a speckled back and the base of its cerata has a prominent white (or sky blue) band. This band, which can be only a large spot in some individuals, is very vivid and so it makes C. rubiginosa recognisable instantly. The digestive diverticulum of C. rubiginosa, which is relatively narrower than that of C. affinis, is apricot or pale fawn brown.
The generic name Caldukia has an interesting history. It is derived from the Aboriginal word “Kalduke” meaning a bunch of feathers, and is an allusion to the way the cerata are bunched on the back of living animals.
Burn, R. (1958) Further Victorian Opisthobranchia. Journal of the Malacological Society of Australia 1(2): 20-36.
Burn, R. & Miller, M.C. (1969) A new genus, Caldukia, and an extended description of the type species, Proctonotus ? affinis Burn, 1958 (Mollusca: Gastropoda: Arminacea: Antiopellidae). Journal of the Malacological Society of Australia 1(12): 23-31.
Miller, M.C. 1970. Two new species of the genus Caldukia Burn & Miller, 1969 (Mollusca: Gastropoda: Opisthobranchia) from New Zealand waters. The Veliger, 12(3): 275-289.
Burn, R. (1989) Chapter 12 Opisthobranchs (Subclass Opisthobranchia). In: Shepherd, S.A. & Thomas, I.M. (Editors) Marine Invertebrates of Southern Australia Part 2, South Australian Government Printer, Adelaide.
Willan, R.C., 2001 (June 7) Caldukia affinis (Burn, 1958). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/caldaffi