Dave Mullins on location

Chelidonura amoena Bergh, 1905 The Chelidonura belong to the Aglajidae family (the tailed slugs) of Headshield Slugs. They are distinguished by having essentially a cylindrical body, a broad headshield usually with sensory cilia arranged on the anterior edge, well-developed parapodia that fold up over the sides of the body to meet, or almost meet, on the midline and two elongated caudal lobes or "tails" (extensions of the posterior shield) with the left being distinctly longer than the right. Chelidonura amoena exhibits all of the above features except for any obvious anterior sensory cilia. It presents with a white background colour bordered by pale yellow margins to the headshield, parapodia and posterior shield including the tails. The white background colour is overlaid with a fine grey or brown reticulum of varying intensity and distribution such that the underlying white shows through as small spots. It possesses a reduced and calcified internal shell that is basically expanded and flattened in shape. Distribution is essentially tropical Western Pacific having been recorded from Japan down through the Philippines, Malaysia, Indonesia, PNG and both east and west coasts of Australia. Diet is believed to consist of small acoel flatworms like many of the Chelidonura genus.

This characteristic of varying colour intensity has lead to the suggestion that perhaps another, more recently described species - Chelidonura electra - is actually only an extreme variant of Chelidonura amoena that lacks any of the darker overlaying pigment or that the intermediate forms are hybrids. That has not as yet been proved so until such time as DNA testing is undertaken we still have two good species.

Chelidonura pallida is another similar-looking species but it has distinctive black and gold lines around the margins of its otherwise white body and appendages.

References:

- Burn R. & Thompson T.E. (1998) Order Cephalaspidea Pp 943-959 in Beesley, P.L., Ross, G.J.B. & Wells, A. (eds) Mollusca: The Southern Synthesis. Fauna of Australia. Vol. 5. CSIRO Publishing: Melbourne, Part B.
- Rudman 1998 - 2010. Chelidonura amoena, Factsheet & Related Messages, Sea Slug Forum, Australian Museum, Sydney.
- Willan R. C. & Cattaneo-Vietti R. (1995) New Data on Chelidonura amoena Bergh, 1905. The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 1995 12: 9-18.

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