Photo Observation of the Month of March - Sea Slugs Anonymous

I know I sound like a broken record, but congratulations to Erik Schogl, once again, for his amazing Photo Observation of the Month of March of the sea slug Pleurobranchus weberi at Camp Cove in Southern Sydney Harbour. Erik remains atop the leaderboard for the Marine Biodiversity of Southern Sydney Harbour project, with 890 observations and 215 species (including this sea slug). This identification was aided by Hsini Lin, the founder of the Sea Slugs of Taiwan group, and a self taught sea slug expert with a staggering 138315 iNaturalist identifications of species within this amazing group of animals.

This sea slug observation is so important because this species has only recently been recorded in Australia. In fact, there are only 13 total records on Atlas of Living Australia, 12 of those records contributed by iNaturalist citizen scientists and 1 record sourced from the Sea Slug Survey in the Gold Coast, also a citizen science led initiative. As a rundown of the ALA records: one record was contributed by co-Director of the Lizard Island Research Station Dr Anne Hoggett in 2011, two were recorded in 2023 on Queensland's Sunshine Coast, 3 were recorded on Queensland's Gold Coast (one in 2020 and two in 2023), 2 were recorded near the entrance of Lake Macquarie in New South Wales in 2023, and 5 (including our observation of the month) were recorded in Sydney Harbour. The remaining observations in Sydney Harbour were all in Chowder Bay at various points in 2022.

Previously, this species was only known from Indonesia and the Philippines, can get quite large (up to 20 cm), and can be distinguished from closely related species in the size of the mantle tubercles, placement of the white circles relative to their tubercles, and completeness of the circles. I will never say no to a new nudie!

This journal post was written by project leader and iNaturalist member, Dr Joseph DiBattista.