Nudibranchs are a group of soft-bodied, marine gastropod mollusks which shed their shells after
their larval stage. Nudibranchs are often casually called sea slugs.
The word "Nudibranch" comes from the Latin nudus "naked" and the Ancient Greek βράγχια
(bránkhia) "gills". Nudibranchs come in all shapes and sizes varying in adult size from
4 mm to 600 mm and occur in seas worldwide. The lifespan of Nudibranchs can range from a
few weeks to a year, depending on the species.
A pair of rhinophores on the Nudibranch's head have scent receptors that allow the Nudibranch to
smell its food or other Nudibranchs. Most Nudibranchs have the ability to withdraw the rhinophores
and gills and hide them if the Nudibranch senses danger.
They are carnivorous, so their prey includes sponges, coral, anemones, hydroids, barnacles, fish
eggs, sea slugs, and other Nudibranchs.
Currently, about 3000+ species of Nudibranchs are known of which roughly 33% have been found on the
Sunshine Coast of Australia.
Nudibranchs are hermaphroditic, thus have a set of reproductive organs for both sexes, but they
cannot fertilize themselves. Nudibranchs typically deposit their eggs within a gelatinous spiral,
which is often described as looking like a ribbon. The number of eggs can vary from as few as just 1
or 2 eggs or as many as an estimated 25 million. The eggs contain toxins from sea sponges as a means
of deterring predators.
Nudibranch laying eggs
We dive with Gary Cobb who is a citizen scientist and owns nudibranch.com.au. He has found over
500 species in the river and 1000+ on the Sunshine Coast. For more detailed information on these awesome creatures please reference Gary's site.