Phylum: Arthropoda, Crustacea Pachygrapsus crassipes Class: Malacostraca Order: Decapoda The lined shore crab Section: Brachyura Family: Grapsidae Taxonomy: Until recently the brachyuran (on either side of the mouth), two pairs of family Grapsidae, the shore crabs, was very maxillae and three pairs of maxillipeds. The large with several subfamilies and little maxillae and maxillipeds attach posterior to taxonomic scrutiny. Based on molecular and the mouth and extend to cover the mandibles morphological evidence, authors (von (Ruppert et al. 2004). The third maxilliped in Sternberg and Cumberlidge 2000; Schubart P. crassipes has merus, lobate and at an et al. 2000; de Grave et al. 2009; Schubart angle (Wicksten 2011). 2011) elevated all grapsid subfamilies to the Carapace: Nearly square in shape family level, reducing the number of species and a little broader than long, transverse lines formally within the Grapsidae. Although or grooves on anterior. Lateral margins are recent molecular evidence suggest that most broad posterior to orbit (Wicksten 2011). Hemigrapsus is no longer within this family, Carapace sides nearly parallel, but arched Pachygrapsus remains one of the few (Fig. 1). members of the Grapsidae sensu stricto Frontal Area: Broad margin that is based on morphological evidence from adults, smooth, slightly arched and half as wide as larvae and molecular data (Schubart 2011). carapace. Four slight lobes present below margin with small lobes at outer corners (Fig. Description 2). Size: Carapace approximately 40 mm in Teeth: One strong lateral carapace width and males are larger than females (Hiatt tooth (below the orbital tooth) (Fig. 2). 1948) (Fig. 1). Mature individuals weighed 15 Pereopods: Merus of each leg broad g. (Gross and Marshall 1960) and measure and bearing a single tooth at each postero- 48 mm in width (Puls 2001). distal angle, except the fifth (last) pair smooth Color: Dark green carapace, with dark red or at distal end, and no sharply distinct teeth blue transverse lines and some light markings (Fig. 3) (Wicksten 2011). Leg shape broad, (Plate 21, Kozloff 1993). Chela white compressed and bristled (Rathbun 1918). ventrally and bright red dorsally (males) Dactyls spinulose (Wicksten 2011). (Wicksten 2011). Chelipeds: Usually subequal and General Morphology: The body of decapod massive. Chela almost smooth with arm and crustaceans can be divided into the wrist striated (Rathbun 1918). Male chela cephalothorax (fused head and thorax) and broad with raised line present on propodus, abdomen. They have a large plate-like fingers spooned. Female chela, on the other carapace dorsally, beneath which are five hand, less broad. pairs of thoracic appendages (see chelipeds Abdomen (Pleon): Females with wide and pereopods) and three pairs of abdomen and male H. oregonensis have maxillipeds (see mouthparts). The abdomen narrow abdomens that exposes the sternum and associated appendages are reduced and at the base (see Sexual Dimorphism, see folded ventrally (Decapoda, Kuris et al. 2007). Fig. 3, Hemigrapsus oregonensis). Cephalothorax: Telson & Uropods: Eyes: Eyes present at anterolateral Sexual Dimorphism: Male and female angle and eyestalks of moderate size with brachyuran crabs are easily differentiable. orbits deep and oblique (Fig. 2). The most conspicuous feature, the abdomen, Antennae: is narrow and triangular in males while it is Mouthparts: The mouth of decapod wide and flap-like in females (Brachyura, crustaceans comprises six pairs of Kuris et al. 2007). Male P. crassipes appendages including one pair of mandibles Hiebert, T.C. 2015. Pachygrapsus crassipes. 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. A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12727 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to [email protected] abdomen is narrow and triangular, exposing Local Distribution: Northernmost boundary sternum at sides (as in Hemigrapsus nudus is 45° N (Newport, Oregon), probably due to and H. oregonensis.) Female abdomen is cold winter temperatures found on protected rounded, wide and hiding sternum in the rocky beaches and in southern Oregon adult. Dimorphism obvious when animals estuaries. only 6 mm wide (Hiatt 1948). Habitat: Prefers hard substrates, especially rocks, jetties and boulders with crevices and Possible Misidentifications crannies covered in algal growth. Also occurs Pachygrapsus species are members of the in Salicornia marshes where Salicornia roots Grapsidae, a family characterized by the provide burrows. carpus of the third maxilliped not articulating Salinity: Most aspects of the biology of P. near the anterior merus angle and by lateral crassipes, in the following categories, were mouth margins that are parallel or convergent described by Hiatt (1948). Osmoregulatory (Wicksten 2011). There is only one local adaptations indicate movement toward Pachygrapsus species, but it may be terrestrial habitat and can regulate against confused with other grapsid crabs from the salt concentrations in the body during periods family Varunidae, characterized by chelae of exposure, and thus maintain a constant morphology, gaping third maxillipeds and body salinity (Jones 1941). Occurs less setose walking legs (Ng et al. 2008). frequently in brackish water than does Pachygrapsus crassipes is superficially Hemigrapsus (Hiatt 1948). similar to the slower Hemigrapsus nudus, but Temperature: Northern limit of range the latter has obvious red spots on its apparently determined by low winter chelipeds, and lacks the dark green color and temperatures and individuals can tolerate transverse striations of P. crassipes. greater temperature fluctuation than can Furthermore, the frontal margin of P. Hemigrapsus (Hiatt 1948). crassipes is straight and it has one lateral Tidal Level: Lives over an extensive vertical tooth, not two (Symons 1964). Two similar range from mean low water to + 2.5 m. shore crabs in the genus Hemigrapsus are H. Pachygrapsus crassipes is found highest in oregonensis, which is smaller, and H. nudus, intertidal of all Pacific Northwest crabs and is with two lateral teeth and a smooth, square especially abundant at the higher levels carapace. The only other species of (upper intertidal, Schmitt 1921) progressing Pachygrapsus, the smaller P. transversus, toward terrestrial habitat (Hiatt 1948). occurs only as far north as California. The However, as blood concentrations of only other locally occurring member of the potassium, calcium, and magnesium increase Grapsidae, Planes cyaneus, is a pelagic more than sodium when animal is desiccated, species that is only found washed ashore on terrestrial adaptation may be inhibited. Also, drift logs with gooseneck barnacles (Kuris et efficiency of the animal's vascular system, al. 2007). Rhithropanopeus harrisii, an affected by osmotic stress, further limits introduced xanthid (Panopeidae) mud crab, ecological range (Gross 1959). occurs locally with shore crabs. It has a Associates: Pachygrapsus crassipes occurs slightly convergent sides, strong dorsal ridges with Hemigrapsus oregonensis in bays, and on its carapace and three sharp carapace with H. nudus on rocky outer shores. , It teeth. competes with both for shelter (Hiatt 1948), but not for food. Fucus (alga) and Salicornia Ecological Information (pickleweed) often provide protection. Range: Type locality is probably Oregon Individuals can be infested by bopyrid isopods (erroneously Hawaii, Hiatt 1948; Wicksten (Southern California, Schmitt 1921). 2011). Known range includes Oregon to Gulf Hemigrapsus oregonensis, H. nudus and P. of California, however there is significant crassipes can be all be host to the nemertean genetic structuring between populations north egg predator, Carcinonemertes epialti, which and south of Pt. Conception, California can negatively impact brood mortality in these (Cassone and Boulding 2006). species (Shields and Kuris 1988). These three species can also serve as intermediate Hiebert, T.C. 2015. Pachygrapsus crassipes. 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. hosts for a variety of parasites including (Schlotterbeck 1976). In P. crassipes, the trematode metacercariae, trypanorhynch lateral spines are not present until the second tapeworm, Polymorphus acanthocephalan zoea stage. The first zoea has no exospines and Ascarophis nematode larvae (Kuris et al. on the telson, is approximately 1.0 mm 2007). (measured from tip of rostrum to tip of telson) Abundance: Ubiquitous in upper intertidal of and has lateral knobs on the second and third rocky areas (Kuris et al. 2007) and more segments, where H. oregonensis has lateral abundant on outer shores than in bays. knobs on only the second segment (Puls 2001). The zoea of Hemigrapsus species Life-History Information and P. crassipes can be differentiated by Reproduction: No pairing or exhibitionism. body and eye size (Schlotterbeck 1976). Copulation occurs when females are soft Pachygrapsus crassipes megalopae have a (post-molting) and copulatory behavior has square carapace and, at 5.6 mm in length and been described by Hiatt (1948) and Bovbjerg