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Colour Patterns in Nudibranchs

Research Scientist: Dr Bill Rudman

Colour patterns in animals are the result of interactions between animals and their environments. Sometimes it is very difficult to understand why a particular animal has a particular colour pattern. In molluscs the shell is an important protection against attack from predators.

The loss of the shell in sea-slugs means that they have had to evolve other means of defence. One easily recognisable way is to evolve a colour pattern which makes you invisible. Such colour patterns are usually called CAMOUFLAGE patterns and there are many remarkable examples amongst the nudibranch sea-slugs.

Species of one nudibranch family, the Chromodorids, have brilliant colour patterns. Dr Rudman's research suggests that their bright colours are a warning to fish alerting them to distasteful chemical poisons which are stored in their skin. This is known as APOSEMATIC colouration.

In south-eastern Australia groups of unrelated species have evolved almost identical colour patterns, many being white with red spots. This MIMICRY has almost certainly evolved as a more efficient way of teaching fish to leave the nudibranchs alone. If fish, instead of having to learn the colour patterns of every species of nudibranch, only have to learn to avoid red-spots, then far fewer nudibranchs will be killed during the fishes' learning period.

camouflage 1		camouflage 2		camouflage 3
camouflage 4		poison glands		bright colours 1
bright colours 2		mimicry

Publications from the project

1. Rudman, W.B. (1981b) The anatomy and biology of alcyonarian feeding aeolid opisthobranch molluscs and their development of symbiosis with zooxanthellae. Zoological Journal of the Linnean Society 72: 219-262.
   
2. Rudman, W.B. (1981c) Polyp mimicry in a new species of aeolid nudibranch mollusc. Journal of Zoology, London, 193: 421-427.
   
3. Rudman, W.B. (1982a) The taxonomy and biology of further aeolidacean and arminacean nudibranch molluscs with symbiotic zooxanthellae. Zoological Journal of the Linnean Society 74: 147-196.
   
4. Rudman, W.B. (1985) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris aureomarginata, C. verrieri and C. fidelis colour groups. Zoological Journal of the Linnean Society 83: 241-299.
   
5. Rudman, W.B. (1986b) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific:Noumea purpurea and Chromodoris decora colour groups. Zoological Journal of the Linnean Society 86(4): 309-353.
   
6. Rudman, W.B. (1986c) Nudibranchs: Nature's thieves. Australian Natural History 22(1): 2-6.
   
7. Rudman, W.B., Avern, G. (1989a) The genus Rostanga (Nudibranchia: Dorididae) in the Indo-West Pacific. Zoological Journal of the Linnean Society 96(3): 281-338.
   
8. Rudman, W.B. (1991) Purpose in Pattern: the evolution of colour in chromodorid nudibranchs. Journal of Molluscan Studies, 57, (T.E. Thompson Memorial Issue): 5-21.

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