LAUSR

Research on heterobranch sea slug diversity in Hong Kong was flourishing in the 1980-90s, with the first checklist and guidebook published and many new species and records documented later. This golden era of sea slug research ended abruptly, and no review nor any extensive collection has been done in the past 20+ years. In view of the extensive revision in heterobranch systematics in recent years, the current checklist can be considered out of date in both nomenclature and composition. Therefore, we are dedicated to providing a synthesis of the current state of knowledge on Hong Kong sea slug diversity by reviewing previous records and engagement of citizen science. An integration of previously published and unpublished records revealed the presence of 186 species, of which 107 species were documented by our citizen science programme with a further report of 71 new records. This yields a total of 257 species from 126 genera, 53 families and ten higher taxa, of which seven species have not been reported elsewhere from Hong Kong. While the present study has markedly illuminated our understanding of sea slug diversity in Hong Kong, the true biodiversity may be underestimated given the high proportion of novel records, especially when many previous records were not herein observed. Hong Kong likely harbours a greater sea slug diversity which awaits discovery from more rigorous sampling and a more inclusive citizen science programme.