Cancer productus Randall, 1839
Common name(s): Red rock crab, Red
crab, Red cancer crab
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Synonyms:
Platycarcinus productus,
Cancer perlatus |
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Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Subclass Eumalacostraca
Superorder Eucarida
Order Decapoda
Suborder Pleocyemata
Infraorder
Brachyura
Superfamily Cancroidea
Family
Cancridae |
Cancer productus, about 12 cm
carapace width, at Sares Head |
(Photo by: Dave Cowles
September 2005) |
Description:
This cancer crab has a dark
tip to the dactyl of the chela (photo).
The
carapace is much wider than it is long, and its dorsal surface is
nearly
smooth and not covered with large bumps or tubercles. The
propodus
of the chela usually has several tubercles (photo).
The widest point of the carapace is at the 8th (next to the last)
lateral
tooth (photo). Dorsal carapace is usually brick red, and up
to 20
cm wide in males and 17 cm in females. The series of five
points
between the eyes are nearly equal in size and extend slightly farther
out
than does that of most cancer crabs, leading to the productus
in
the name. The dactyls of the walking legs have short
setae.
The carapace color pattern of juveniles is very different from that of
adults (photo), often white
or with red and white
stripes.
How to Distinguish from
Similar Species:
The other large, common cancer crab species in the Rosario area is C.
magister, which does not have a dark tip to the
dactyl of the chela,
and its carapace is widest at the 10th and last lateral
tooth. C.
antennarius has red spots on the underside of the carapace.
Note: Species formerly in genus Cancer have been recently
subdivided into several genera (Ng
et al., 2008; Schweitzer
and Feldmann, 2010). Of our local genera, Cancer, Romaleon,
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
because Metacarcinus
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). Romaleon
can be distinguished from Cancer
and Metacarcinus
because it has a distinct tooth on the anterior third of the
posterolateral margin of the carapace while the other two genera do
not.
Geographical Range:
Alaska to San
Diego
Depth Range:
Low intertidal to 90
m
Habitat:
Rocky and soft bottoms.
Most common around rocks. Often found half-buried in sand
under rocks
during the day; more active at night.
Biology/Natural History:
Predators
include sand and kelp bass and sculpin (on juveniles) and seabirds such
as gulls and pigeon guillemots. Prey include barnacles and
smaller
crabs, amphipods, sea cucumbers, polychaetes, many other intertidal
invertebrates,
as well as dead fish. At least 42 prey species have been
noted.
Are an important threat to commercial oyster beds. Crabs
raised on
thick-shelled species such as Mytilus
californianus developed even stronger
claws. Mating occurs
in summer after a female has molted. Males will often guard a
female
who is preparing to molt, by holding her under his abdomen.
This
may last for several weeks until she molts. He then guards
her until
her exoskeleton hardens again. Gravid females may be found
from October
to June. Females may carry from 172,000 to 597,000 eggs on
the pleopods
of the abdomen. Males overwinter in shallow areas, while
females
seem to overwinter in deeper water. Red rock crabs cannot
osmoregulate
and so are not found in areas of low salinity. Near Vancouver
Island,
adults have more epibionts than do juveniles (McGraw,
2006). Common epibionts include barnacles
(especially Balanus
crenatus) on the dorsal surface, green, red, and
brown algae (especially
on the antennae), tube-dwelling polychaetes (mainly on the ventral
surfaces),
hydrozoans (mainly on ventral surfaces and limbs), bryozoans
(especially
Membranipora
membranacea) on any region of the carapace. A few
have sponge,
tunicate, or mollusk epibionts.
Dudas
et al. (2005) found that the common local cancer crabs Metacarcinus
magister (Dungeness crab) and Cancer
productus preferred
the thin-shelled introduced varnish clam Nuttallia
obscurata to the thicker-shelled clams Leukoma
staminea and Venerupis
philippinarum if access to all was equally
easy. However,
Nuttallia
obscurata typically lives deeper in the sediment
than do Leukoma
staminea or Venerupis
philippinarum. If they had to dig for
them, Metacarcinus
magister still ate more Nuttallia
obscurata than it did of the other clam species,
but C. productus'
preference switched to Leukoma
staminea and Venerupis
philippinarum.
References:
Dichotomous Keys:
Coffin,
1952
Flora
and Fairbanks, 1966
Hart,
1982
Kozloff
1987, 1996
Smith
and Carlton, 1975
Wicksten,
2009
General References:
Brusca
and Brusca, 1978
Gotshall,
1994
Gotshall
and Laurent, 1979
Harbo,
1999
Hinton,
1987
Jensen,
1995
Johnson
and Snook, 1955
Kozloff,
1993
McConnaughey
and McConnaughey, 1985
Morris
et al., 1980
Niesen,
1994
Niesen,
1997
O'Clair
and O'Clair, 1998
Ricketts
et al., 1985
Sept,
1999
Scientific Articles:
Dudas,
Sarah E., Iain J. McGaw, and John F. Dower, 2005.
Selective crab
predation on native and introduced bivalves in British
Columbia.
Journal of Experimental Marine Biology and Ecology 325:1 pp 8-17
Dufur, Peter L., Brian R. McMahon, and Charles E. Booth,
1983.
Analysis of hemolymph oxygen levels and acid-base status during
emersion
'in situ' in the red rock crab, Cancer productus.
Biological
Bulletin 165: 582-590
McGraw,
Iain J., 2006. Epibionts of sympatric species of
Cancer crabs
in Barkley Sound, British Columbia. J. Crustacean Biology
26:1 85-93
Ng,
P.K.L., D. Guinot, and P.J.F. Davie, 2008.
Systema Brachyurorum: part I. An annotated checklist of
extant
brachyuran crabs of the world. Raffles Bulletin of Zoology,
Supplement 17 pp. 1-286 (Clicking on link will load a pdf of the long
article)
Reese, J.E., and C. P. Mangum, 1994. Subunit
composition and O2
binding of the crustacean Hemocyanins: Interspecific
Relationships.
Biological Bulletin 187: 385-397
Schram,
Frederick R. and Peter K.L. Ng, 2012. What is
Cancer? Journal of Crustacean Biology 32:4 pp. 665-672
Schweitzer,
C.F. and R.M. Feldmann, 2000.
Re-evaluation of the Cancridae Latereille, 1802 (Decapoda: Brachyura)
including three new genera and three new species.
Contributions
to Zoology 69:4 pp. 223-250
Wekell, J.C., R. M. Lorenzana, M. Hogan, and H. Barnett,
1996.
Survey of paralytic shellfish poison and domoic acid in Puget Sound
predatory
gastropods. J. Shellfish Research 15(2): 231-236
Web sites:
General Notes and
Observations: Locations, abundances,
unusual behaviors:
In seawater tanks this species will readily attack most
smaller animals,
including smaller crabs, shrimp, clams, snails, hermit crabs,
etc.
They crack them into pieces with their powerful claws. This
species
should not be kept with other species.
The tip of the dactyl on the chela of Cancer productus
is dark,
and the propodus has several tubercles, some of which are usually
arranged
in longitudinal lines.
The carapace of Cancer productus has 10 teeth
lateral to the
eye. The carapace is widest at the 9th tooth.
In this individual (live) one can see the fringes of setae on the legs.
This large male is holding a smaller female, in preparation for her
molt.
Mating takes place after the female has molted.
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Some of the color patterns possible
on a Cancer productus
juvenile. Note the possible sequence of patterns from left to
right
as the crab grows larger. |
Crab from subtidal, Admiralty Beach.
Photo by Dave Cowles July 2007 |
Photo by Dave Cowles July 2006 |
Crab at Keystone Ferry jetty, July 2007.
Photo by Bethany Reiswig |
One of the color patterns possible on a Cancer
productus juvenile.
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This small juvenile Cancer
productus, found subtidally
at Admiralty Beach, often assumes an unusual defense posture with the
chelae
held lengthwise to the body when disturbed (left) rather than crosswise
to the body as is usually seen (right). Both photos are of
the same
crab, which is the same individual as the crab at left in the table
above.
Photos by Dave Cowles, July 2007
Another juvenile, found near Rosario in 2021
An underwater photo by Kirt Onthank, Jule 2007
Since the female gonopores are hard during intermolt, mating cannot
occur except during a molt. Male crabs (upper) pick up female
crabs
(lower) before they molt. The carry them underneath
themselves, protecting
them until the female molts. At that time sperm transfer
takes place.
The male continues to guard the female until after her new exoskeleton
has hardened, then releases her.
Underwater photo by Kirt Onthank, June 2007
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Authors and Editors of Page:
Dave Cowles (2005): Created original page
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