Phylum: Arthropoda, Crustacea Hemigrapsus oregonensis Class: Malacostraca Order: Decapoda Section: Brachyura A hairy shore crab Family: Varunidae Taxonomy: The brachyuran family and associated appendages are reduced and Grapsidae, the shore crabs, was a very large folded ventrally (Decapoda, Kuris et al. 2007). family with several subfamilies and little Cephalothorax: taxonomic scrutiny, until recently. Based on Eyes: Eyestalks and orbits molecular and morphological evidence, moderately sized (Rathbun 1918) and eyes at authors (von Sternberg and Cumberlidge antero-lateral angle (Fig. 2). 2000; Schubart et al. 2000; de Grave et al. Antennae: 2009; Schubart 2011) elevated all grapsid Mouthparts: The mouth of decapod subfamilies to family level, reducing the crustaceans comprises six pairs of number of species formally within the appendages including one pair of mandibles Grapsidae. Recent molecular evidence has (on either side of the mouth), two pairs of placed Hemigrapsus species within the maxillae and three pairs of maxillipeds. The Varunidae, but this is currently debated where maxillae and maxillipeds attach posterior to some authors still refer to them as members the mouth and extend to cover the mandibles of the Grapsidae sensu lato (Ng et al. 2008; (Ruppert et al. 2004). Wicksten 2012) and others have adopted the Carapace: Rectangular or square in new familial designation (e.g. Kuris et al. shape and wider than long with rounded 2007). Besides the higher taxonomic antero-lateral margins. Carapace surface is classifications, the known specific synonym smooth and bears three teeth (two lateral that for H. oregonensis is Pseudograpsus are posterior to postorbital) (Wicksten 2012) oregonensis (Wicksten 2012), which is not on antero-lateral margin, no transverse lines currently used. (Fig. 1). Frontal Area: Less than half the Description width of the carapace with two prominent Size: Carapace 34.7 mm in width and 28.4 frontal lobes and deep median sinus mm in length (Rathbun 1918; Wicksten 2012) (Wicksten 2012). Frontal margin without teeth (Fig. 1). The carapace of reproductive (Hemigrapsus, Kuris et al. 2007). individuals measures approximately 50 mm Teeth: Two lateral carapace teeth, (Puls 2001). with deep sinuses, below outer orbital tooth Color: Dull brownish green, gray to uniform (Fig. 2). light gray or muddy yellow with no red spots Pereopods: More or less hairy on chelipeds (compare H. nudus, Plate 21, (compare to H. nudus) (Fig. 1). Kozloff 1993; Kuris et al. 2007). Nearly white Chelipeds: Stout and equal or almost or yellow forms of both Hemigrapsus species equal in size. Dactyls hollowed in shallow have been reported (Ricketts and Calvin groove and male with mat of fine hair on 1971; Wicksten 2012). propodus. General Morphology: The body of decapod Abdomen (Pleon): Females with wide crustaceans can be divided into the abdomen and male H. oregonensis have cephalothorax (fused head and thorax) and narrow abdomens that exposes the sternum abdomen. They have a large plate-like at the base (see Sexual Dimorphism, Fig. 3). carapace dorsally, beneath which are five Telson & Uropods: pairs of thoracic appendages (see chelipeds Sexual Dimorphism: Male and female and pereopods) and three pairs of brachyuran crabs are easily differentiable. maxillipeds (see mouthparts). The abdomen The most conspicuous feature, the abdomen, Hiebert, T.C. 2015. Hemigrapsus oregonensis. 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/1794/12711 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to [email protected] is narrow and triangular in males while it is cyaneus, is a pelagic species that is only wide and flap-like in females (Brachyura, found washed ashore on drift logs with Kuris et al. 2007). Male H. oregonensis have gooseneck barnacles (Kuris et al. 2007). a narrow abdomen that exposes the sternum Rhithropanopeus harrisii, an introduced (Fig. 3) and hairy chelipeds. Females have a xanthid (Panopeidae) mud crab, is sometimes wide abdomen and ho hairy patch on palm found with H. oregonensis. It has a slightly (only a few bristles). convergent sides, strong dorsal ridges on its carapace and three sharp carapace teeth. Possible Misidentifications Hemigrapsus species were formally members Ecological Information of the Grapsidae, a family characterized by Range: Type locality is Puget Sound, the carpus of the third maxilliped not Washington. Known range includes Alaska to articulating near the anterior merus angle and Baja California, Mexico (Wicksten 2012). by lateral mouth margins that are parallel or Local Distribution: Common in many convergent (Wicksten 2012). The genus Oregon bays including Yaquina, Siletz, Hemigrapsus may now be a member of the Tillamook, Netarts, Coos and Coquille family Varunidae (see Taxonomy) (Ricketts and Calvin 1971). characterized by chelae morphology, gaping Habitat: Quiet water, rocky habitats within third maxillipeds and setose walking legs (Ng estuaries, gravel shores but prefers muddy et al. 2008). Two Hemigrapsus species occur habitats (Ricketts and Calvin 1971) and salt locally, H. oregonensis and H. nudus. marshes. On muddy bottoms of estuaries Hemigrapsus nudus, the purple shore crab, is and on eelgrass and amongst Enteromorpha. larger than H. oregonensis, is “naked” (i.e. not Also in muddy spots on the open rocky coast. hairy) on its walking legs and has chelipeds The two Hemigrapsus species can co-occur, with conspicuous red spots. Hemigrapsus but one usually finds one or the other and H. nudus lives mostly on the rocky open coast, oregonensis prefers quieter water than does but is also found in salt marshes (Knudsen H. nudus (Kozloff 1993). 1964). Hemigrapsus oregonensis has been Salinity: Hemigrapsus oregonensis tolerates called a small, bleached edition of H. nudus salinity ranging from 17.5–31.6 (San (Ricketts and Calvin 1971). The following Francisco, California), likes freshwater seeps features are particularly useful in (Garth and Abbott 1980) and cannot tolerate differentiating the two Hemigrapsus species: much desiccation. 1) H. oregonensis has a marked frontal notch Temperature: Small animals most tolerant to where H. nudus has a shallow depression, 2) temperature extremes (Todd and Dehnel the lateral spines of H. oregonensis are sharp 1960). and distinctly separated from the side but H. Tidal Level: Found at very high and very low nudus spines are not, 3) The dactyls of tide levels, but usually lower intertidal than H. walking legs 1–3 are long in H. oregonensis nudus (Todd and Dehnel 1960). Individuals and short in H. nudus and 4) the dactyl of the can be found at higher tidal reaches of the fourth walking leg is round in H. oregonensis mudflats (Ricketts and Calvin 1971) and mid and flat in H. nudus (Kuris et al. 2007). The to low intertidal of bays as well as sublittorally final varunid crab that occurs locally is the (Kuris et al. 2007). introduced Chinese mitten crab, Eriocheir Associates: Hemigrapsus oregonensis has sinensis, but this species is very large and many associates. In gravel, isopods Idotea easily differentiable from either Hemigrapsus and Gnorimosphaeroma, and occasionally H. species. nudus (Kozloff 1993). Alga Ulva Pachygrapsus crassipes, a member of (sublittorally), and pickleweed, Salicornia (in the Grapsidae, is a dark green crab with marshes) (Kuris et al. 2007; Wicksten 2012). many transverse dark red striations on its legs The parasitic castrating isopod, Portunion and carapace (H. oregonensis is smooth), its conformis, is sometimes within the frontal margin is straight and it has one lateral perivisceral cavity of H. oregonensis (Garth tooth, not two (Symons 1964). The only other and Abbott 1980) with infection rates up to locally occurring grapsid crab, Planes 40% (Jaffe et al. 1987; Kuris et al. 2007). Hiebert, T.C. 2015. Hemigrapsus oregonensis. 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. Hemigrapsus oregonensis, H. nudus and P. second and third segments (Puls 2001). The crassipes can all be host to the nemertean larvae of H. oregonensis are also a bit smaller egg predator, Carcinonemertes epialti, which and more slender than that of the closely can negatively impact brood mortality in these related H. nudus (Jaffe et al. 1987). The zoea species (Shields and Kuris 1988). These of Hemigrapsus species and P. crassipes can three species can also serve as intermediate be differentiated by body and eye size hosts for a variety of parasites including (Schlotterbeck 1976). Hemigrapsus trematode metacercariae, larval oregonensis megalopae are rectangular and trypanorhynch tapeworms, as well as can be recognized by a posterior telson Polymorphus acanthocephalan and nematode without setae (other than uropod setae) and a (Ascarophis) larvae (Kuris et al. 2007). carapace that is 1.4–1.7 mm in length and Abundance: In great numbers, benthically, 1.1–1.3 mm in width. The first in-star stage is in estuaries and usually common on gravelly reached after approximately 4–5 weeks (Puls substrates (Wicksten 2012). 2001). Juvenile: Very small animals have a marked