Phylum: Arthropoda, Crustacea Class: Multicrustacea, Malacostraca, Eumalacostraca Petrolisthes cinctipes Order: Eucarida, Decapoda, Pleocyemata, Anomura The flat porcelain crab Family: Galatheoidea, Porcellanidae Taxonomy: Petrolisthes cinctipes is and Eyes: The eyestalks of P. cinctipes has been a widely used name for this spe- contain neurosecretory cell bodies (z-organs) cies. There are, however, several junior that regulate regeneration, molting and oocyte synonyms including Porcellana cinctipes, maturation (Kurup 1964a). Porcellana rupicola, and Petrolisthes rupico- Antenna: Very long, and often folded lus (for all synonyms see Haig 1960; Wick- posteriorly over carapace sides (Fig. 1). First sten 2011). (basal) joint of antennal peduncle is short and not reaching upper margin of carapace. Description Mouthparts: The mouth of decapod Size: Individuals up to 24 mm in length crustaceans comprises six pairs of appendag- (carapace width) (Puls 2001; Wicksten es including one pair of mandibles (on either 2011). The illustrated specimen (from Coos side of the mouth), two pairs of maxillae and Bay) is 14 mm in length and weighs 1.7 g. three pairs of maxillipeds. The maxillae and Color: Dark blue-brown and somewhat iri- maxillipeds attach posterior to the mouth and descent (see Plate 20, Kozloff 1993). An- extend to cover the mandibles (Ruppert et al. tennae dark red, maxillipeds bright red- 2004). Second maxillipeds in P. cinctipes are orange and legs blue banded with white highly developed for filter feeding (see Food) (Schmitt 1921). White comma-like marks with long fine hairs and specialized shape for are sometimes present ventrally and cheli- channeling water currents (Fig. 4). The color peds bear a red spot at dactyl base, while of the palps of maxilliped three are of walking legs have a yellow median band on taxonomic importance: blue in P. eriomerus propodus. Dactyls yellow with narrow brown and orange in P. cinctipes (Kozloff 1993; band. Individuals near molting are blue in Kuris et al. 2007). color (Wicksten 2011). Carapace: Round with carapace front General Morphology: The body of decapod triangulate (Petrolisthes, Haig 1960). Cara- crustaceans can be divided into the cepha- pace surface is finely granulate and not lothorax (fused head and thorax) and abdo- rough. No epibranchial (anterolateral) spines men. They have a large plate-like carapace and epimera and lateral portions of carapace dorsally, beneath which are five pairs of tho- are entire (Figs. 1, 2). Carapace about as racic appendages (see chelipeds and pere- long as wide (Wicksten 2011). opods) and three pairs of maxillipeds (see Frontal Area: Triangular and strongly mouthparts). The body of the Porcellani- deflexed with conspicuous median groove dae is crab-like and convex longitudinally (Fig. 1). with small fifth legs resting on carapace (Fig. Teeth: 1) and the abdomen and associated ap- Pereopods: Waking legs 2–4 with a pendages are reduced and folded ventrally. few coarse spines on dactyl, propodus and The body and chelae of Petrolisthes are flat- carpus, but not on merus (Fig. 1). Merus of tened (Kuris et al. 2007). third leg is inflated and carpus is without setae Cephalothorax: 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. Petrolisthes cinctipes. 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. while propodus and dactyl bear setae. Fifth broad, not longer than broad as in Petrolis- legs small, elevated and rest on carapace thes. There are three local species: P. (Figs. 1, 3). holosericus, P. pubescens and P. rudis (Kuris Chelipeds: Equal (or almost), broad et al. 2007). and flattened, not thick and rough Petrolisthes species, on the other (Petrolisthes, Schmitt 1921; Kuris et al. hand, have a flattened body and chelae, che- 2007), covered with fine granules (as in lae of equal size with carpus longer than it is carapace) but without setae. Carpus almost wide. Petrolisthes cinctipes is recognizable invariably 1 1/2 times longer than wide and by characteristics of the cheliped carpus. The anterior and posterior margins converge carpus has a long anterior lobe that extends distally (Schmitt 1921; Kuris et al. 2007) more than 1/4 total carpus length, is smooth (Fig. 1). Posterior margin with ridge of and hairless and with margins that converge tubercles flanked by teeth distally. distally (Kuris et al. 2007). Five Petrolisthes Prominent lobe at inner angle (P. cinctipes, species are reported to occur from central Kuris et al. 2007) (Fig. 1). A short tuft of hair California to Oregon including P. cinctipes, P. between fingers present ventrally, but che- cabrilloi, P. eriomerus, P. manimaculis and P. lae are generally hairless (Figs. 1, 2). Merus rathbunae. with conspicuous lobe on anterior margin. Of those, P. eriomerus is superficially (Wicksten 2011). quite like P. cinctipes (Kozloff 1993). This Abdomen (Pleon): Abdomen symmetrical, crab lives under rocks in gravelly substrates short and permanently folded under thorax. and is a little smaller than P. cinctipes. The Seven abdominal plates (Petrolisthes) (Figs. carpus of the chelipeds in P. eriomerus is 1, 2). twice as long as wide (not 1 1/2 times as long) Telson & Uropods: Seventh plate of telson and the carpus margins are parallel, not con- forms tail fan (Fig. 2). Uropods attached to verging. Also, there is no prominent lobe at abdominal segment five. the inner angle and the carpus has scattered Sexual Dimorphism: Not obvious superfi- tubercules, not a finely granulated surface as cially. Inside telson, males have single pleo- in P. cintctipes. Ventrally, the outer edge of pods on abdominal plate two and females the maxillipeds in P. eriomerus is bright blue, have long, branched pleopods on plates 3–5 not red orange (Kozloff 1993; Kuris et al. (not shown). 2007). These two species exhibit a non- overlapping vertical distribution, where P. eri- Possible Misidentifications omerus occurs in the low intertidal and P. Porcelain crabs (Porcellanidae) are cinctipes is found in the mid to high intertidal flattened dorso-ventrally and are often found (Jensen and Armstrong 1991). in small cracks and crevices. Their third P. cabrilloi, P. manimaculis and P. maxillipeds bear long setae, which they use rathbunae are all reported from California: to filter feed and their fifth walking legs are Petrolisthes cabrilloi from Morro Bay, Califor- modified into brushes for grooming. There nia south to Baja California, Mexico and ap- are two genera of porcelain crabs in our ar- parently replaces populations of P. cinctipes ea, Petrolisthes and Pachycheles. Members south of Point Conception, California; P. of the Pachycheles have a thick, rough body manimaculis from Bodega Bay, California and chelae, chelae are unequal, tuberculate south to Baja California, Mexico; P. rathbunae or granular and hairy, not smooth. Further- from Monterey, California to Isla Guadalupe, more, the carpus of the chela is as long as Mexico (Wicksten 2011). 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] Ecological Information Found only at shore stations and not by Range: Type locality is erroneously indicat- dredging (San Francisco Bay, Schmitt 1921). ed as in Hawaii, but is likely to be near Mon- Associates: Associates include mussels, tu- terey, California (Wicksten 2011). Known nicates, sponges, nudibranch Onchidoris, range includes British Columbia to Point chiton Mopalia, shore crabs Hemigrapsus, Concepcion, California and also islands offs- Cancer oregonensis, predatory gastropod hore of southern California, and Baja Califor- Nucella, and the sea star Pisaster ochraceus. nia (Haig 1960). Abundance: Very common (Haig 1960) (up Local Distribution: Outer, more marine to 860 individuals per m2, Monterey, Califor- portions of large estuaries. Occurs locally in nia) (Barnard et al. 1980). When found, P. Coos Bay (e.g. Pigeon Point) and in Netarts cinctipes is usually abundant (MacGinitie and Bay. MacGinitie 1949; Kuris et al. 2007). Habitat: Protected, semi-protected rocky Life-History Information coasts under rocks and amongst mussel Reproduction: Females ovigerous every beds (Ricketts and Calvin 1971; Kuris et al. month of the year but April, May, September, 2007). Prefers open shores and clear water October and November (Haig 1960; Barnard (Haig 1960) and is not tolerant of sand and et al. 1980) and evidence shows that multiple silt (Jensen and Armstrong 1991; Wicksten males (1–3) may contribute to each brood 2011). (Toonen 2004). In Coos Bay, March is the Salinity: Collected at salinities of 30. month in which the greatest number of fema- Temperature: A mid to high intertidal spe- les are found with developing young. Eggs P. cinctipes cies, is exposed to a wide range are a little over 800 µm in diameter, deep of temperature (0–32˚C, Stillman and Som- scarlet to maroon when extruded and become ero 2000). Recent research involving physi- brownish red as they advance cal factors associated with climate change developmentally (Gonor and Gonor 1973a; P. cinctipes has used as a model organism Barnard et al. 1980). (e.g. Somero 2010). Stress by thermal vari- Larva: Petrolisthes cinctipes larvae were de- ation, more than other physical factors (e.g. scribed by Gonor and Gonor (1973a, b). De- pH, salinity), negatively effects P. cinctipes velopment proceeds via two zoeal larval stag- (Paganini et al. 2014). However, when ac- es and a filter feeding megalopa, each P. climated for a short period of time (6 hrs), marked by a molt (Puls 2001). Porcelain crab cinctipes can increase thermotolerance zoea are recognizable as larval stages by (Ronges et al.