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Search is on for elusive Sydney sea slug


Brigid Veale
17 November 2016

A search of a very different kind will be under way in Sydney’s waterways this weekend, to find a highly elusive sea slug – Macleay’s Spurilla.

The search is part of the second annual Sydney Sea Slug Census, which contributes directly to Southern Cross University’s marine biodiversity research program. The event is being organised by the Underwater Research Group, Sydney, with generous support from Adreno Scuba and Abyss Scuba Diving.

Volunteer divers will have 24 hours to search for nudibranchs and other sea slugs in a quest to photograph the largest number of species and become the best spotter for 2016.

Professor Steve Smith, director of Southern Cross University’s National Marine Science Centre in Coffs Harbour, has been co-ordinating sea slug censuses in locations along the east coast since 2013.

“With rapid life cycles and a reliance on specific food sources, seas 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.

“Because of their spectacular colours and diverse body forms, sea slugs are very popular subjects for underwater photographers, making them an obvious choice for citizen science programs documenting marine biodiversity.”

This year the census will incorporate a specific search for an important and highly elusive species – Macleay’s Spurilla. Originally described from Sydney Harbour in 1864, this species is being sought by Australia’s senior nudibranch expert, Dr Richard Willan, to “solve a 152-year-old ‘cold case’ in the world of nudibranchs”.

“This species lives in intertidal boulder-fields, but recent, extensive searching in the region has so far failed to find a single specimen. We are hoping that this local species has not become a casualty of the rapid spread of another member of the genus, Spurilla braziliana, which was recorded in Australia for the first time in 2006 and is now the most common boulder-field nudibranch in many parts of the NSW coast,” Professor Smith said.

Bare Island will be the main location for the Sydney Sea Slug Census.

Photo: Macleay's Spurilla.