New species record in Taiwan: "Broad-thumb Bayberry Crab" discovered in Little Liuqiu

Reported by You T-Ru / Comprehensive report

Broad-thumb Bayberry Crab (Actumnus digitalis) This crab was discovered by the American Fisheries Society during their 1904 expedition to investigate tropical Pacific waters, found in Tahiti. Over 100 years later, it was first discovered in Taiwan’s intertidal zone in Little Liuqiu by Coach Su Jianming, marking it as a new species record for Taiwan and increasing the island’s crab species count to 113 across 25 families.


▲ Broad-thumb Bayberry Crab (Actumnus digitalis). (Photo / Provided by Pingtung County Government)

The Broad-thumb Bayberry Crab is a small crab with a shell width of only about 6 mm, belonging to the Pilumnidae family (hairy crabs) and the Actumnus genus. It exhibits typical features of the Pilumnidae family, such as having bristly hairs and short downy fuzz scattered across its body, but lacks spines on the front edge of its carapace, which instead appears smooth with slight undulations. Its chelae (claws) are short, stout, and asymmetrical—especially the movable finger of the larger claw, which is broad like a human “thumb,” hence the name “Broad-thumb Bayberry Crab.” It is often active in tide pools and adept at hiding by burrowing into the sand. Despite its tiny size, its bright coloration makes it hard to miss. Only two individuals have been recorded in Little Liuqiu so far, making it extremely rare and precious. After being documented via video, they were released back into the intertidal zone.


▲ The Broad-thumb Bayberry Crab, skilled at hiding in the sand. (Photo / Provided by Pingtung County Government)

With an area of approximately 6.8 square kilometers and a coastline of about 12 kilometers, Little Liuqiu Island’s rich crab records indicate that it is an important marine habitat in the Western Pacific and a hotspot for marine biodiversity conservation. Given the abundant intertidal life on Little Liuqiu, visitors are encouraged to tread carefully to avoid accidentally harming these precious creatures.