Colourful defence

A nudibranch of the genus Chromodoris.
Image: Gary Cranitch


26 May 2010
The nudibranch specimen of the genus Chromodoris collected on the CReefs Ningaloo expedition may not be a new species, but it will help marine scientists better understand these amazing creatures.
Nudibranchs, sometimes called sea slugs, are soft-bodied mollusks that shed their shells after the larval stage. Nudibranchs of the superfamily Doridoidea breathe through branchial plumes clumped on their backs instead of gills: the word "nudibranch" means naked gills in Latin. The horn-like tentacles, called rhinophores, on their heads are chemical sensors that lead them to food or other members of their species. Many also have protruding structures called cerata that aid in respiration.
Nudibranchs range in size from two to 60 centimetres and can weigh up to 1.5 kilograms. Most are carnivorous, feeding on sponges, bryozoans, anemones, barnacles and even other sea slugs. Some species store algae in their outer tissues to gain energy from the algae's photosynthesis.
The bright colour of many nudibranchs warns would-be predators that they are dangerous: some species produce toxic secretions, while others store the stinging cells from anemones or bluebottles, which they eat, in sacs at the tips of their cerata and use these for defence.
This specimen of Chromodoris will be examined by Dr Arthur Anker and his colleagues at the Florida Museum of Natural History.