Phylum: Arthropoda, Crustacea Cancer productus Class: Multicrustacea, Malacostraca, Eumalacostraca Order: Eucarida, Decapoda, Pleocyemata, Brachyura, The red rock crab Eubrachyura, Heterotremata Family: Cancroidea, Cancridae Taxonomy: Despite recent confusion re- Carapace: Broadly oval, uneven and garding a variety of cancrid genera, the tax- slightly convex. Widest at ninth antero-lateral onomy of Cancer productus has remained tooth (Fig. 1) (Wicksten 2012). stably within the genus Cancer (Harrison Frontal Area: Markedly pronounced and Crespi 1999; Schweitzer and Feldmann beyond eyes, with five nearly equal teeth (Fig. 2000; Kuris et al. 2007; Wicksten 2012). 2). Teeth: Ten antero-lateral teeth Description (counting orbital tooth), nine large teeth that Size: Carapace 97–174 mm in length and become more acute posteriorly. up to 157.5 mm in width (Schmitt 1921; Pereopods: Dactyls thickly fringed Rathbun 1930). Females with carapace above and below. length up to 158 mm and males up to 200 Chelipeds: Dactyls dark-tipped and mm (Puls 2001). hands rough dorsally. Carpus wrinkled, with Color: Dark red dorsally, lighter ventrally, single tooth at inner angle (Queen 1930). legs mottled red and juveniles striped (Fig. Abdomen (Pleon): Abdomen narrow in male, 3). broad in female (e.g. see Cancer magister, General Morphology: The body of decapod Fig. 3). crustaceans can be divided into the cepha- Telson & Uropods: lothorax (fused head and thorax) and abdo- Sexual Dimorphism: Male and female brach- men. They have a large plate-like carapace yuran crabs are easily differentiable. The dorsally, beneath which are five pairs of tho- most conspicuous feature, the abdomen, is racic appendages (see chelipeds and pere- narrow and triangular in males while it is wide opods) and three pairs of maxillipeds (see and flap-like in females. Additionally, males mouthparts). The abdomen and associated have one large chelae and two pleopod pairs appendages are reduced and folded ventral- specialized for copulation however, the third ly (Decapoda, Kuris et al. 2007). and fourth pleopods are absent. Females, on Cephalothorax: the other hand, have all four pleopod pairs, Eyes: Eyestalks short, orbits small. each with long setae for egg attachment Antenna: Antennules folded length- (Brachyura, Kuris et al. 2007). wise, antennal flagella short and hairy (Queen 1930). Possible Misidentifications Mouthparts: The mouth of decapod According to some authors, the genus crustaceans comprises six pairs of append- Cancer comprises 23 species (Harrison and ages including one pair of mandibles (on ei- Crespi 1999 but see Schweitzer and Feld- ther side of the mouth), two pairs of maxillae mann 2000). This genus is differentiated from and three pairs of maxillipeds. The maxillae other brachyuran genera by the broadly oval and maxillipeds attach posterior to the carapace, presence of five frontal teeth and mouth and extend to cover the mandibles antennules that fold back over carapace. (Ruppert et al. 2004). Characters unique to Cancer productus in- A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Hiebert, T.C. 2015. Cancer productus. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. clude ten antero-lateral teeth, carapace wid- rocky shores (Garth and Abbott 1980). est at ninth tooth, bright red color and black- Habitat: Individuals appear to prefer gravel, tipped cheliped dactyls (Kuris et al. 2007). rock, and hard bottom – C. productus does There are eight Cancer species not burrow and lacks straining apparatus for known locally (Kuris et al. 2007). The most sand removal (Ricketts and Calvin 1971). Al- morphologically similar to C. productus is C. so found in rocky tidepools and among magister, which also has 10 antero-lateral eelgrass (Ricketts and Calvin 1971; Garth and teeth and five subequal frontal teeth (Kuris Abbott 1980). Adults tend to bury themselves et al. 2007). However, the carapace of C. into soft sand as is seen in C. magister, magister is widest at the tenth tooth, is more although less frequently (McGaw 2004). subtly pigmented and does not have black Salinity: Collected at 30. In San Francisco tipped dactyls (Wicksten 2012). The two Bay salinity tolerance ranges from 21.7 to species are often collected together in crab 33.3 (Schmitt 1921). pots. Cancer antennarius, like C. productus, Temperature: Collected at 11–17°C in the is dark red with spots ventrally and with San Francisco Bay area (Schmitt 1921). black tipped chelae. However the carapace Tidal Level: Intertidal to about 79 m and oc- width in C. antennarius is widest at the curs closer to shore than C. magister (Puls eighth tooth and there are a total of 11 2001). antero-lateral teeth (Wicksten 2012). Associates: Cancer oregonensis is a small, oval crab Abundance: Common (Carlton and Kuris with 12–13 total teeth. The remaining four 1975). species have nine antero-lateral teeth Life-History Information (sometimes ten in older specimens, Reproduction: In C. productus, mating Wicksten 2012). Cancer branneri is a small occurs June–August (Puget Sound) (Knudsen species (35 mm) that is rare intertidally and 1964; Jaffe et al. 1987). When the female is recognizable by cheliped dactyls that are about to molt, male C. productus clasps the long, straight, black and spiny. Cancer gra- female and copulation takes place after cilis is also small (27 mm) has white-tipped molting (i.e. female shell is soft). Fertilization cheliped dactyls and C. jordani (25 mm) has is internal and egg deposition occurs months a hairy carapace and sharp curving teeth. later in December–January, at which point Cancer anthonyi, the yellow rock crab, is lar- eggs are bright orange. All decapod ger than the previous three at 52 mm and crustacean females attach recently laid has black-tipped cheliped dactyls (Kuris et gelatinous egg masses to their pleopods. The al. 2007; Wicksten 2012). Populations of C. outer embryo membrane thickens and a productus, C. anthonyi (southern California) strand develops that attaches each embryo to and C. magister support commercial fishe- pleopod setae (Decapoda, Kuris et al. 2007). ries (Kuris et al. 2007). Eyespots and chromatophores are easily Ecological Information visible in advanced embryos and make them Range: Kodiak, Alaska, to Magdalena Bay, appear gray when ready to hatch. Zoea Baja California (Schmitt 1921). larvae hatch by early April (Knudsen 1964). A Local Distribution: Occurs in a variety of second brood is sometimes produced (Jaffe local Oregon estuaries including Coos, Ya- et al. 1987). quina, Umpqua, Coquille, Tillamook Larva: The larvae of C. productus have been (Gaumer et al 1973) on semi-protected described (Trask 1970; Roesijadi 1976). Lar- A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] val development proceeds via a prezoea dermis separates from the old cuticle and a (Roesijadi 1976) followed by a series of zo- dramatic increase in epidermal cell growth oc- ea (five total, telson with single lateral spine curs. Post-molt individuals will have soft at each fork, Lough 1975) and megalopae shells until a thin membranous layer is depos- stages, each marked by a molt. The zoea ited and the cuticle gradually hardens. During and megalopae of cancrid species are a molt decapods have the ability to regener- difficult to distinguish. The larvae of C. ate limbs that were previously autotomized productus, C. oregonensis and C. magister (Kuris et al. 2007). Research has shown, are morphologically similar (Puls 2001), but however, that regenerated limbs handicap C. can be differentiated (e.g. variation in setal productus foraging and predatory abilities morphology, see Trask 1970). Cancer (Brock and Smith 1998). productus zoea are planktotrophic and have Food: Cancer productus individuals are large compound eyes and four spines: one scavengers and predators on other each dorsal and rostral and two lateral (see crustaceans, especially barnacles and other Fig. 1, Trask 1970; Martin 2014), which are crabs (Knudsen 1964) as well as molluscs lacking in prezoeae (Roesijadi 1976). Larval and polychaete worms. Zoea reportedly in- size (measured from tip of rostrum to tip of gest Dendraster excentricus pluteus larvae, telson) proceeds from 2.5 mm (Zoea I and but their efficiency reduces with pluteus size telson with pair of lateral exospines) to and age (Rumrill et al. 1985). approximately 6 mm (Zoea V) (Trask 1970; Predators: Adults are commercially and rec- Puls 2001). The megalopae of C. productus reationally harvested for food. Additional are about half the size of C. magister predators include octopus, fish and birds megalopae (3.4–3.6 mm from rostrum to (Knudsen 1964). Larval forms are predated posterior carapace and approximately 2 mm by filter and plankton feeders (herring, salm- at wides point) (Trask 1970). Larvae have on, and other fishes). been observed swarming in May (Friday Behavior: Individuals are dominant and stalk Harbor, Jaffe et al. 1987). Hatching zoea to prey in tidepools at night (Ricketts and Calvin the megalopa stage requires 97 days in the 1971). They are also active in daylight and lab (Trask 1970). The megalopae of C. individuals can aggregate by sex and age, de- oregonensis and C. productus were pending on egg-laying and molting cycles described by DeBrosse et al. 1989 (see Fig. (Knudsen 1964). 1-2, 3-4, DeBrosse et al. 1989). Bibliography Juvenile: Juveniles are often brightly col- ored and possess several to many spots 1. BROCK, R. E., and L. D. SMITH. 1998.