Hemigrapsus
A genus of varunid crabs with Pacific origins and Atlantic invasions.
Hemigrapsus is a genus of varunid crabs. Of its fifteen recognized species, thirteen are native almost entirely to the Pacific Ocean. Two species, however, have spread to the North Atlantic. The genus’s natural range is mostly Pacific, with one exception: *Hemigrapsus affinis* lives along the Atlantic coast of South America, from Brazil’s Cape São Roque down to the San Matías Gulf in Argentina. Another species, *H. estellinensis*, is almost certainly extinct; it was found only in a hypersaline spring in the Texas Panhandle, roughly 500 miles from the sea. *H. sanguineus* has been introduced from its native East Asia to several places: it now occurs along North America’s Atlantic coast from Portland, Maine, to North Carolina, along western Europe from northern Spain to Denmark, and in the northern Adriatic and northern Black Seas. *H. takanoi*, also native to East Asia, has been introduced to western Europe, where it ranges from northern Spain to Denmark, including the westernmost Baltic Sea. The fifteen currently recognized species are: *H. affinis*, *H. crassimanus*, *H. crenulatus*, *H. estellinensis* (extinct), *H. gibbus*, *H. longitarsus*, *H. nudus*, *H. octodentatus*, *H. oregonensis*, *H. pallipes*, *H. penicillatus*, *H. sanguineus*, *H. sexdentatus*, *H. sinensis*, and *H. takanoi*.
Quick Facts
- Taxon
- Hemigrapsus
- Type Species
- Hemigrapsus crassimanus
- Type Species Authority
- Dana, 1851
Facts from the source article.
Lore & Background
The natural range of Hemigrapsus is restricted to the Pacific Ocean, with the exception of Hemigrapsus affinis, which lives along the Atlantic coasts of South America from Cape São Roque in Brazil to the San Matías Gulf in Patagonia, Argentina. Hemigrapsus estellinensis is almost certainly extinct, but was endemic to a hypersaline spring in the Texas Panhandle, 500 miles from the sea. Populations of Hemigrapsus sanguineus have been introduced from its native range in East Asia to several places, now ranging along the Atlantic coast of North America from Portland, Maine to North Carolina, along the West European coast from northern Spain to Denmark, and in the northern Adriatic Sea and northern Black Sea. Hemigrapsus takanoi, native to East Asia, has been introduced to western Europe, extending from northern Spain to Denmark, including the westernmost Baltic Sea area.
Reader's Guide
Hemigrapsus holds significance as a genus that demonstrates both endemism and invasive potential. The presence of Hemigrapsus affinis along the Atlantic coasts of South America is a notable exception to the genus's otherwise Pacific distribution, while the extinct Hemigrapsus estellinensis represents a unique adaptation to a hypersaline inland habitat far from the sea. The introductions of Hemigrapsus sanguineus and Hemigrapsus takanoi to the North Atlantic region illustrate the capacity of these crabs to establish populations across multiple continents and seas, including the Adriatic, Black, and Baltic Seas. The genus comprises fifteen currently recognized species, with Hemigrapsus estellinensis marked as almost certainly extinct. The species list includes names from various authors spanning the 19th and 20th centuries, reflecting a long history of taxonomic study. The legacy of Hemigrapsus lies in its biogeographic patterns, from isolated inland springs to widespread coastal invasions, offering insights into crab dispersal and adaptation.
Did You Know?
- Hemigrapsus sanguineus has been introduced from East Asia to the Atlantic coast of North America, western Europe, the northern Adriatic Sea, and the northern Black Sea.
- Hemigrapsus affinis is the only species in the genus native to the Atlantic Ocean, ranging from Brazil to Argentina.
- Two Hemigrapsus species have been introduced to the North Atlantic region: H. sanguineus and H. takanoi.
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