The Taming of Smeagol? A New Population and an Assessment of the Known Population of the Critically Endangered Pulmonate Gastropod Smeagol hilaris (Heterobranchia, Otinidae)

The genus Smeagol consists of five named species of air-breathing marine slugs (restricted to southern Australia and New Zealand) and three undescribed taxa from southern Japan. Only one species, S. hilaris, is known to be from New South Wales (NSW), and it previously had a known distribution limited to one site, Merry Beach on the south coast. This diminutive invertebrate is classified as critically endangered in NSW due to its extremely restricted distribution and concern about its historically declining numbers. Accordingly, the aims of this study were to survey the known population of S. hilaris at Merry Beach and to explore other potentially suitable sites, using a visual census method, to determine if further populations or species exist in NSW. The resulting quantitative surveys of the known population and a new population at Storm Bay, Kiama, NSW, are reported here. DNA barcoding of a similar to 650 bp segment of the mitochondrial cytochrome c oxidase I (COI) gene for several individuals from each population confirmed the conspecificity among the two populations. The population at Merry Beach was found to remain viable, while the discovery of the new population of S. hilaris represents a doubling of the known global populations of this species. Details of the highly-specialised niche habitat occupied by Smeagol in New South Wales and recommendations for ongoing management are documented.

Automated summary

The genus Smeagol includes five named species of air-breathing marine slugs, with restricted distribution to southern Australia, New Zealand, and southern Japan. The critically endangered S. hilaris from New South Wales has had a known distribution limited to Merry Beach. This study surveyed the known population at Merry Beach and discovered a new population at Storm Bay, doubling the known global populations of this species. DNA barcoding confirmed the conspecificity among the populations and recommendations for ongoing management are provided.