Phylum: Arthropoda, Crustacea Cancer magister Class: Multicrustacea, Malacostraca, Eumalacostraca Order: Eucarida, Decapoda, Pleocyemata, Brachyura, Dungeness or market crab Eubrachyura, Heterotremata Family: Cancroidea, Cancridae Taxonomy: Recent morphological studies Antenna: Antennules folded length- have elevated the subgenus Metacarcinus wise and antennal flagella short and, more or to genus level (Schweitzer and Feldmann less, hairy (Rathbun 1930). 2000). However, molecular work does not Mouthparts: The mouth of decapod always support the monophyly of this or crustaceans is comprised of six pairs of ap- other cancrid genera (Harrison and Crespi pendages including one pair of mandibles (on 1999). Although many researchers have either side of the mouth), two pairs of maxillae switched to the name Metacarcinus magister and three pairs of maxillipeds. The maxillae (e.g. Wicksten 2011; Rasmuson and Shanks and maxillipeds attach posterior to the mouth 2014; Dunn and Young 2014), we follow and extend to cover the mandibles (Ruppert current local intertidal guides and reviews of et al. 2004). the species that retain the name Cancer Carapace: Broadly oval, uneven but magister (e.g. Kuris et al. 2007; Rasmuson not highly sculptured and with granular tex- 2013). ture. Carapace width greatest at tenth tooth (Fig. 1). Postero-lateral margin is unbroken, Description entire and without teeth. The antero-lateral Size: Carapace 120.7 mm in length, 177.8 margin meets the postero-lateral margin with mm in width. Up to 1.36 kg in weight, distinct angle (Fig. 1). though average weight of four-year old (i.e. Frontal Area: No rostrum. Narrow and fully mature) males is 0.91 kg (Rasmuson with five unequal teeth, not markedly pro- 2013). duced beyond outer orbital angles. Middle Color: Light reddish brown, darkest anterior- tooth largest and more advanced than outer ly, often light orange below (Rathbun 1930), pair. The outer pair form inner orbital angles sometimes with gray-purple mottling dorsal- (Fig. 2). ly. Inner sides of anterior dactyls and Teeth: Ten antero-lateral teeth, count- propodi crimson, but tips not darkly pigment- ing the orbital tooth. All teeth are pointed and ed (Rathbun 1930; Kuris et al. 2007). with anterior serrations. The tenth tooth is General Morphology: The body of decapod large and projecting. crustaceans can be divided into the cepha- Pereopods: Rough above, broad and lothorax (fused head and thorax) and abdo- flat (especially the propodus and dactylus of men. They have a large plate-like carapace last pair). dorsally, beneath which are five pairs of tho- Chelipeds: Dactyls not pigmented and racic appendages (see chelipeds and pere- dactyl spines on upper surface. The fixed opods) and three pairs of maxillipeds (see finger is much deflexed. The hand (propodus) mouthparts). The abdomen and associat- has six carineae on upper outer surface and ed appendages are reduced and folded ven- the wrist (carpus) has a strong inner spine trally (Decapoda, Kuris et al. 2007). (Fig. 1). Cephalothorax: Abdomen (Pleon): Abdomen narrow in male, Eyes: Eyestalks short, orbits small. 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. and L. Rasmuson. 2015. Cancer magister. 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 Biolo- gy, Charleston, OR. broad in female (Fig. 3). productus, is dark red with spots ventrally and Telson & Uropods: One feature that may with black tipped chelae. However, the be taxonomically relevant to the placement carapace width in C. antennarius is widest at of this species within Metacarcinus or Can- the eighth tooth and there are a total of 11 cer (see taxonomy) is the telson morpholo- antero-lateral teeth (Wicksten 2011). Cancer gy. The genus Metacarcinus is character- oregonensis is a small, oval crab with 12–13 ized by males with a rounded tip to the tel- total teeth. The remaining four species have son, while the males of Cancer species have nine antero-lateral teeth (sometimes ten in a more sharply pointed telson tip (Schram older specimens, Wicksten 2011). Cancer and Ng 2012). branneri is a small species (35 mm) that is Sexual Dimorphism: Male and female rare intertidally and recognizable by cheliped brachyuran crabs are easily differentiable. dactyls that are long, straight, black and The most conspicuous feature, the abdo- spiny. Cancer gracilis is also small (27 mm) men, is narrow and triangular in males while has white-tipped cheliped dactyls and C. jor- it is wide and flap-like in females (Fig. 3). dani (25 mm) has a hairy carapace and sharp Additionally, males have one large chelae curving teeth. Cancer anthonyi, the yellow and two pleopod pairs specialized for copu- rock crab, is larger than the previous three at lation, however, the third and fourth pleo- 52 mm and has black-tipped cheliped dactyls pods are absent. Females, on the other (Kuris et al. 2007; Wicksten 2011). Popula- hand, have all four pleopod pairs, each with tions of C. productus, C. anthonyi (southern long setae for egg attachment (Brachyura, California) and C. magister support commer- Kuris et al. 2007). cial fisheries (Kuris et al. 2007). Due to the extensive commercial fishery for C. magister Possible Misidentifications (Alaska to California) there are many extensi- According to some authors, the ge- ve reviews on this species (e.g. Wild and Tas- nus Cancer comprises 23 species (Harrison to 1983; Pauley et al. 1989; Rasmuson 2013). and Crespi 1999). This genus is differentiat- ed from other brachyuran genera by the Ecological Information broadly oval carapace, presence of five Range: Type locality is San Francisco Bay frontal teeth and antennules that fold back (Schmitt 1921). Known range includes Alaska over carapace. Characters unique to Can- to Monterey Bay, California (Ricketts and Cal- cer magister include 10 antero-lateral teeth, vin 1971). carapace widest at tenth tooth and the lack Local Distribution: Most local northwest es- of black-tipped cheliped dactyls. tuaries and offshore waters. Also near shore There are eight Cancer species and within bays in summer months (Ricketts known locally (Kuris et al. 2007). Cancer and Calvin 1971). productus, the most morphologically similar Habitat: Individuals are found in many sub- to C. magister, also has 10 antero-lateral strates, from mud to sand, gravel and rock teeth and five subequal (but nearly equal) (Schmitt 1921). Cancer magister appears to frontal teeth (Kuris et al. 2007). However, its prefer sand (Weymouth 1914) and mud with cheliped dactyls are black tipped, its cara- eelgrass in bays (Kozloff 1974). Juveniles pace is widest at the ninth tooth and its body and adults tend to bury themselves into soft color can be uniformly brick red (characters sand (Jaffe et al. 1987; McGaw 2005). In par- not observed in C. magister) (Wicksten ticular, females must be buried 5–10 cm deep 2011). Cancer antennarius, like C. to attach embryos to their pleopods (Fisher 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] and Wickham 1976). ter clasp females and copulation takes place Salinity: In Coos Bay, individuals were co- over several days (Snow and Nielsen 1966; llected at salinities from 11–35 (Dunn and Rasmuson 2013). Fertilization is internal and Young 2013). Juvenile crabs are more tole- occurs after molting and egg deposition rant to low salinity (Hunter and Rudy 1975; occurs months later. Eggs are approximately Robinson and Potts 1979). Dunn and 390–420 µm in diameter and females carry Young (2013) found that the salinity toleran- broods up to 2.5 million from October to ce of adult crabs may provide them refuge December. Eyespots and chromatophores from the nemertean egg predator that is mo- are easily visible in advanced embryos (80 re prevalent in areas of high salinity. days at 10˚C, Jaffe et al. 1987; Kuris et al. Temperature: 2007). The larval duration ranges from 89– Tidal Level: 143 days (average 130), hatching occurs bet- Associates: Both male and female C. mag- ween January and March with settlement bet- ister are usually infested with the nemertean ween April and August in Oregon and Was- egg predator Carcinonemertes errans hington (Table 3.1, Rasmuson 2013). See (Wickham 1979a, b; Dunn and Young 2013). Rasmuson 2013 (Fig. 3.2) for C. magister life These worms occur all over the body of cycle. adults, particularly near the joints or ab- Larva: Larval development proceeds via a dominal flap and are transferred from males series of zoea (five total) and megalopae to females during copulation where they, stages, each marked by a molt. Cancer mag- eventually move toward the egg mass. The ister zoea are planktotrophic and have large life-cycle of this nemertean is dependent on compound eyes and four spines: one each and corresponds to that of C. magister dorsal and rostral and two lateral (see Fig. 31, (Kuris 1993). Puls 2001; Rasmuson 2013; Martin 2014). Abundance: Commercial catch in Oregon is Larval size (measured from tip of rostrum to cyclic in nature and has ranged from a high tip of telson) proceeds from 2.5 mm (Zoea I) of 15,112,000 kg (2006) to a low of 224,000 to 9 mm (Zoea V) (Puls 2001). The zoea of kg (1928) (Fig. 3.3, Rasmuson 2013). cancrid species are difficult to distinguish but Population fluctuations appear to be driven the megalopae of C.