Hemigrapsis takanoi, commonly known as the Brush-clawed Shore crab, was first described by Asakura & Watanabe in 2005. They are native to parts of Asia, from Japan, Russia, to China. They are a non-native invasive species in the UK, and were first recorded in Essex in 2014 (although was reported in 1997 in the English Channel). There are currently 399 occurrences in the UK from NBN Atlas. While worldwide, on iNautualist, there are over 600 research-grade observations, and on the Global Biodiversity Information Facility (GBIF), over 30,000 observations

This species grows to about 2.5cm and features a distinctly square-shaped carapace (shell), with a completely straight edge running between the eyes and three tooth-like structures on either side. They are covered in tiny, dark spots across their legs and shell, while their claws have white tips.

You can tell the sexes apart by looking closely at their anatomy and markings:

Abdomen: Females feature a wide, rounded abdomen, whereas males have a narrow, pointed abdomen.

Claws: Males have a distinctive patch of fuzzy fur (setae) at the base of their claws.

Hemigrapsus takanoi is morphologically very similar to another invasive species within its genus: the Asian Shore Crab (Hemigrapsus sanguineus). To accurately tell them apart, look for these two diagnostic features:

Leg markings: H. sanguineus features distinct, dark reddish-purple banding across its walking legs (not its claws). In contrast, H. takanoi lacks this banding, displaying a more uniform colour pattern on its legs.

Adult male claw characteristics: The males look completely different when you inspect the inner palm of their claws. H. takanoi males possess a patch of fuzzy fur (setae), while H. sanguineus males feature a smooth, fleshy, bulbous projection (vesicle) instead. To see male photo comparison between the two species, click here.

Habitat

Hemigrapsus takanoi prefer sheltered, low-energy environments with fine-sediment accumulation, commonly inhabiting estuaries, saltmarshes, and harbours. They are highly adaptable and often seek out artificial structures, oyster beds, or debris for cover.

The species produces free-swimming, planktonic larvae that are easily drawn into the ballast water tanks of large vessels. Transported across global shipping routes, these larvae are later released into new waters, allowing Hemigrapsus takanoi to establish and spread throughout parts of Europe and the UK.

References

Dauvin, J.-C., Tous Rius, A., and Ruellet, T. (2009) Recent expansion of two invasive crabs species Hemigrapsus sanguineus (de Haan, 1835) and H. takanoi Asakura and Watanabe 2005 along the Opal Coast, France. Aquatic Invasions 4(3): 451–465.

Epifanio, C. E. (2013) Invasion biology of the Asian shore crab Hemigrapsus sanguineus: A review. Journal of Experimental Marine Biology and Ecology 441: 33–49.

NBN Atlas (2026) Hemigrapsus takanoi Asakura & Watanabe, 2005. Available at: https://species.nbnatlas.org/species/NHMSYS0001697250 (Accessed: 24 May 2026).

Northern Ireland Environment Agency (2024) Asian Shore Crab & Brush Clawed Crab: Invasive non-native identification guide (Version 3). Invasive Species Northern Ireland. Available at: https://invasivespeciesni.co.uk/wp-content/uploads/2024/10/NIEA-ID-Guide-Hemigrapsus-spp-Asian-Shore-Crab-V3-Oct24-1.pdf (Accessed: 24 May 2026).