As with all Cancer crabs,
this species has 5 teeth between the eyes. Its carapace
is widest at the 9th tooth lateral to the eyes, and behind this point
is a distinct 10th tooth. The tips of the chelae
are white (photo), and there
are no spiny ridges
on the carpus,
of the chelae
(although there are two blunt teeth on the dorsal ridge of the propodus)
(photo). The carapace
is slightly convex dorsally. The dactyls
of the pereopods
(walking legs) are cylindrical. The dorsal surface of the
of the legs is purple in many individuals. Carapace
width to 11.5 cm (males) or 10.6 cm (females) but usually not over 6
Metacarcinus gracilis (Dana,
Schweitzer and Feldmann, 2000
Common name(s): Graceful rock
Graceful crab, Slender
|Metacarcinus gracilis, about 5
width, from 100 m depth, San Juan Channel
|(Photo by: Dave
How to Distinguish
magister has a carapace
widest at the 10th tooth, with no teeth behind that point, and also has
spiny ridges on the carpus, propodus,
of the chela.
It also has more flattened dactyls
on the pereopods
and the dorsal surface of the upper parts of the legs is not purple.
Note: Species formerly in genus Cancer have been
subdivided into several genera (Ng
et al., 2008; Schweitzer
and Feldmann, 2010). Of our local genera, Cancer and Metacarcinus have a
carapace wider than long plus only scattered setae on the carapace
margins and legs while Glebocarcinus
has a carapace of approximately equal length and width, often with
granular regions and with setae along the edges; and setae on the outer
surface of the chela as well as on the legs. Metacarcinus can be
distinguished from Cancer
has anterolateral carapace teeth which are distinct and sharp plus the
male has a rounded tip to the telson, while Cancer
has anterolateral carapace teeth which are low and lobed, separated by
deep fissures plus the male has a sharply pointed telson (Schram
and Ng, 2012).
Sound, Alaska to Baja California, Mexico
Intertidal to 174 m
Mainly subtidal on sand and
mud, sometimes near eelgrass beds. May be on pilings.
is a scavenger, or eats small invertebrates. Predators
sculpin, starry flounder, the seastar Astropecten verrelli,
the giant octopus Enteroctopus
dofleini. Females usually are found
buried in the mud.
Seasonally found in bays but cannot osmoregulate and does not tolerate
brackish conditions. In Puget Sound eggs were borne from
to April. Males protect females after mating.
juveniles often cling to large jellyfish such as Pelagia
and Fairbanks, 1966
and Carlton, 1975
and Snook, 1955
et al., 1980
and O'Clair, 1998
General Notes and
Observations: Locations, abundances,
The tips of the chelae
are white. There are no spiny ridges on the carpus,
of the chelae,
though there are two spines or tubercles
on the dorsal ridge of the dactyl.
The appendages seen covering the mouth are the maxillipeds,
which are found in all crabs. The white objects between the maxillipeds
are the hardened tips of the mandibles.
|This female C. gracilis, 8.5
width, was found at March Point. She appears to be gravid
eggs). The eggs, however, are much smaller and
crab eggs usually are, leading me to suspect that she may be
by a rhizocephalan
sacculinid barnacle. However, the "eggs"
did not form a
sac-like structure as usually seen in rhizocephalans.
||Raising the abdomen shows the dark gray and black
The female was docile and made little attempt to escape or to pinch.
||A view through the microscope shows the mass is
composed of a large
number of tiny, slightly flattened, egg-like objects attached to her
Note the tip of her chela
at the top right for size. I will have to watch for more
to see whether these tiny, dirty-looking eggs are the norm for Cancer
gracilis. Photos by Dave Cowles July 2007
This view of a Padilla Bay crab shows the purple legs seen in many
individuals. Photo by Dave Cowles July 2008
This squeak-clean individual I found in the Rosario Seawater System
reservoir tank before starting up the seawater system in June 2016.
To get there, the crab would have had to pass through the
intake filter (maximum clearance 1 mm) the previous summer, be pumped
up the hill to the reservoit, remain in the tank 5-10 cm of water in
the bottom of the tank while the rest of the water drained out at the
end of the summer, and then survive and grow to this size in the
perhaps 1-2 cm deep coating of silt on
the bottom of the tank in total darkness for over 9 months
until we opened the seawater system again. No doubt the crab
is so clean because it has never had to deal with algal overgrowth in
the darkness. Carapace
width is 4 cm.
Authors and Editors of Page:
Dave Cowles (2006): Created original page