Elusive sea slug sighted in Sydney census

Published in the November 2016 issue

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A highly elusive sea slug – Macleay’s Spurilla – which has not been seen for years has been found by Southern Cross University’s Professor Stephen Smith during the second annual Sydney Sea Slug Census this month.

The Sydney Sea Slug Census, which contributes directly to Southern Cross University’s marine biodiversity research program, was organised by the Underwater Research Group, Sydney, and attracted around 24 divers.


Spurilla macleayi (Macleay’s Spurilla) – 15mm long. Photo: Professor Stephen Smith

Professor Smith, director of Southern Cross University’s National Marine Science Centre in Coffs Harbour, said at least 52 nudibranchs and other sea slugs were identified, an increase from 43 species last year.

“With rapid life cycles and a reliance on specific food sources, sea slugs have the potential to be important indicators of environmental change. Indeed, since the Sea Slug Census program commenced at Nelson Bay in 2013, the Southern Cross University team has documented substantial range extensions into subtropical and warm temperate waters for more than 20 tropical species,” Professor Smith said.

“The popularity of sea slugs, which have spectacular colours and diverse body forms, with recreational divers makes them an obvious choice for citizen science programs documenting marine biodiversity.”

This year’s census incorporated a specific search for an important and highly elusive species – Macleay’s Spurilla. Originally described from a sighting in Sydney Harbour in 1864, recent extensive searching in the region had failed to find a single specimen.

Professor Smith said he was thrilled to find specimens of Macleay’s Spurilla.

“This is an important discovery because the original specimen, from which the species was described in 1864, has been lost. Nudibranch scientists can now designate a new type specimen – a neotype – which will become the ‘gold standard’ for the species.”

The Sydney Sea Slug census was supported by Adreno Scuba and Abyss Scuba Diving.

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