Comprehensive Description

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Comprehensive Description

The Bay Shore Crab (Hemigrapsus oregonensis) is typically found in quiet water and rocky habitats within estuaries, especially on gravelly substrates. It is less abundant on the open coast, but does occur there, especially in coves where there is some seepage of fresh water onto the shore. Hemigrapsus oregonensis has a nearly rectangular carapace (upper shell). It tends to be grayish green, with conspicuous fringes of hairs on its legs, and lacks the purple spots on the pincers of the first pair of legs that are characteristic of the closely related H. nudus (which is usually reddish, has legs that are not especially hairy, and tends to be found in more exposed rocky situations). Hemigrapsus oregonensis feeds primarily on seaweeds, especially Ulva and related green algae. By day, these crabs remain hidden under debris or in burrows they have excavated, which may be especially conspicuous in the muddy banks of tidal ditches. This species is common in salt marshes all along the northern Pacific coast (the related Hemigrapsus nudus is scarce in California salt marshes, although it is abundant on rocky shores). (Kozloff 1993)


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© Shapiro, Leo

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