How to Distinguish from Similar Species: Hemigrapsus oregonensis also has 3 anterolateral teeth but no purple spots on the chelipeds and the legs have abundant setae. Pachygrapsus crassipes (Oregon and south) has transverse lines and 2 anterolateral teeth on the carapace.
Larvae in the first zoeal stage can be distinguished from zoea of H. oregonensis because H. oregonensis has lateral projections on only abdominal segment 2 while H. nudus has lateral projections on abdominal segments 2 and 3 (Lee and Ko, 2008).
Geographical Range: Yakobi Island, Alaska to Bahia de Tortuga, Mexico. Uncommon below central CA.
Depth Range: Mostly intertidal
Habitat: Under rocks and in cracks. Also high in some estuaries.
Does not live in
burrows, as Hemigrapsus oregonensis often
does. The chela
of males, as of H. oregonensis and P.
crassipes, have a prominent
tuft of hairlike setae on the palm. This species is an
and can tolerate both hypo- and hyperosmotic conditions. In
Sound feeds on diatoms, desmids, and small Ulva and
green algae scraped from rocks with the tips of the chelae.
feed on a few animal products, such as amphipods and the eggs of Nucella
and other whelks. In Puget Sound, females carrying eggs are
from January to mid-July; especially in April. Female may
400 to 36,000 eggs. This species sometimes has the pasasitic
conformis in the perivisceral cavity, and the eggs may be
by the tiny Nemertean worm Carcinonemertes epialti.
include gulls white-winged scoters, Anthopleura
anemones, and staghorn and tidepool sculpins. Nucella
lamellosa seems to be attracted to the scent of
this crab but is
not known to be a predator.
Flora and Fairbanks, 1996
Kozloff 1987, 1996
Smith and Carlton, 1975
General Notes and Observations: Locations, abundances, unusual behaviors:
This species seems to be less tolerant of hypoxia than is is H. oregonensis. In places where their range overlap it is usually found higher in the intertidal and on more sandy/less muddy substrate.
A related species, H. sanguineus (Asian shore crab) on the New England coast was shown to prefer animal prey such as small mussels and barnacles, even though it could also feed on algae. When starved or in crowded conditions it ate algae, but if given a free choice it chose invertebrates. The authors speculated that the species may have an important effect on competition and succession among intertidal attached species. Source: Brousseau, Diane J. and Jenna A. Baglivo, 2005. Laboratory investigations of food selection by the asian shore crab, Hemigrapsus sanguineus: algal versus animal preference. J. Crust. Biol. 25(1): 130-134 (abstract)
Authors and Editors of Page:
Dave Cowles (2005): Created original page