Hemigrapsus Nudus Class: Malacostraca Order: Decapoda Section: Brachyura the Purple Shore Crab Family: Varunidae

Phylum: Arthropoda, Crustacea Hemigrapsus nudus Class: Malacostraca Order: Decapoda Section: Brachyura The purple shore crab Family: Varunidae

Taxonomy: The brachyuran family Cephalothorax: Grapsidae, the shore crabs, was a very large Eyes: Eyestalks and eyes of family with several subfamilies and little moderate size with eyes that are at antero- taxonomic scrutiny, until recently. Based on molecular and morphological evidence, lateral angles (Fig. 2). Grapsid species authors (von Sternberg and Cumberlidge apparently have keen vision (Wicksten 2011). 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 and 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 2011) and others have adopted the Carapace: Flat, smooth, punctate new familial designation (e.g. Kuris et al. (Schmitt 1921) and bears three teeth (two 2007). Besides the higher taxonomic lateral that are posterior to postorbital) classifications, the known specific synonym (Wicksten 2011). Square in shape, with for H. nudus is Pseudograpsus nudus rounded antero-lateral margins (Rathbun (Wicksten 2011), which is not currently used. 1918) and no transverse lines (compare to P. crassipes) (Fig. 1). Posteriorly, carapace is Description flat (Wicksten 2011) (Fig. 1). Size: Carapace 56.2 mm in width and 48 mm Frontal Area: Very slightly rounded in length (Rathbun 1918; Wicksten 2011) (Fig. and without prominent lobes (Fig. 2). 1). An adult male from Coos Bay, was 32 mm Teeth: Two carapace teeth below the in width and weighed 17.5 g (wet weight). orbital tooth, which are lateral, while the last Color: Red, purple, or whitish with chelipeds tooth is small (Fig. 2) (Wicksten 2011). that are red-spotted (compare to H. Pereopods: Naked (without hair) and oregonensis, Plate 21 Kozloff 1993; Kuris et rather short (Schmitt 1921) with short dactyls al. 2007) (Fig. 1). Although coloration is (Fig. 1) (Wicksten 2011). generally species-specific among grapsid Chelipeds: Smooth, equal or almost crabs, nearly white or yellow forms of both equal in size with curved fingers (Wicksten Hemigrapsus species have been reported 2011). Chelipeds stout, mottled above, with (Wicksten 2011). teeth on margins and with small round red General Morphology: The body of decapod spots (Fig. 1). Male with inflated palms and a crustaceans can be divided into the patch of fine hair on inner surface. cephalothorax (fused head and thorax) and Abdomen (Pleon): Females with wide abdomen. They have a large plate-like abdomen and male H. nudus have narrow carapace dorsally, beneath which are five abdomens that exposes the sternum at the pairs of thoracic appendages (see chelipeds base (see Sexual Dimorphism, Fig. 3). and pereopods) and three pairs of Telson & Uropods: maxillipeds (see mouthparts). The abdomen Sexual Dimorphism: Male and female and associated appendages are reduced and brachyuran crabs are easily differentiable. folded ventrally (Decapoda, Kuris et al. 2007). The most conspicuous feature, the abdomen,

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12710 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to [email protected] is narrow and triangular in males while it is has one lateral tooth, not two (Symons 1964). wide and flap-like in females (Brachyura, The only other, locally occurring grapsid crab, Kuris et al. 2007). Male H. nudus have a Planes cyaneus, is a pelagic species that is narrow abdomen, exposing the sternum at the only found washed ashore on drift logs with base (Fig. 3) and the palm of the male gooseneck barnacles (Kuris et al. 2007). cheliped with a patch of long, fine hair. Rhithropanopeus harrisii, an introduced Females have a wide abdomen, hiding the xanthid (Panopeidae) mud crab, is sometimes sternum (Fig. 3), and only a few isolated found with H. oregonensis and potentially H. bristles on the palm of the cheliped. nudus. It has a slightly convergent sides, strong dorsal ridges on its carapace and three Possible Misidentifications sharp carapace teeth. Hemigrapsus species were formally members of the Grapsidae, a family characterized by Ecological Information the carpus of the third maxilliped not Range: Type locality is Puget Sound, articulating near the anterior merus angle and Washington (Ricketts and Calvin 1971). by lateral mouth margins that are parallel or Known range includes Sitka, Alaska, to Gulf convergent (Wicksten 2011). The genus of California (Rathbun 1918). Uncommon in Hemigrapsus may now a member of the Southern California (Garth and Abbott 1980; family Varunidae (see Taxonomy) Jaffe et al. 1987; Wicksten 2011). characterized by chelae morphology, gaping Local Distribution: Coos, Siletz, and third maxillipeds and setose walking legs (Ng Tillamook Bay estuaries (and probably more et al. 2008). Two Hemigrapsus species occur Oregon estuaries) in rocky, brackish habitats. locally, H. oregonensis and H. nudus. Habitat: Semi-protected and protected rocky Hemigrapsus nudus, the purple shore crab, is coasts and bays. Prefers coarse sand to larger than H. oregonensis, is “naked” (i.e. not gravel substrates overlain with large rock hairy) on its walking legs and has chelipeds cover (Schmitt 1921; Kuris et al. 2007). In with conspicuous red spots. Hemigrapsus salt marshes, but not as commonly nudus lives mostly on the rocky open coast, encountered as H. oregonensis, and in but is also found in salt marshes (Knudsen burrows and under driftwood. Less common 1964). Hemigrapsus oregonensis has been in California salt marshes (Kozloff 1993). called a small, bleached edition of H. nudus Hemigrapsus nudus is common in mid tide (Ricketts and Calvin 1971). The following pool regions (Ricketts and Calvin 1971) and is features are particularly useful in found in areas of swift water and large differentiating the two Hemigrapsus species: boulders (Puget Sound, Knudsen 1964). 1) H. oregonensis has a marked frontal notch Hemigrapsus nudus can be found in more where H. nudus has a shallow depression, 2) exposed situations than H. oregonensis and the lateral spines of H. oregonensis are sharp withstands desiccation better (large and distinctly separated from the side but H. specimens). The two Hemigrapsus species nudus spines are not, 3) The dactyls of do co-occur, but one usually finds one or the walking legs 1–3 are long in H. oregonensis other (Kozloff 1993). and short in H. nudus and 4) the dactyl of the Salinity: Occurs in outer shore full strength fourth walking leg is round in H. oregonensis seawater, brackish and hyper-saline and flat in H. nudus (Kuris et al. 2007). The (estuarine marsh) waters. Can endure low final varunid crab that occurs locally is the salinities better at high temperatures (Todd introduced Chinese mitten crab, Eriocheir and Dehnel 1960). sinensis, but this species is very large and Temperature: Hemigrapsus nudus easily differentiable from either Hemigrapsus individuals can tolerate temperatures up to species. 33.6˚C but are more tolerant of cold than Pachygrapsus crassipes, a consistent warm temperatures and modify their behavior member of the Grapsidae, is a dark green to regulate body temperature (McGaw 2003). crab with many transverse dark red striations Survival is most poor with low temperature on its legs and carapace (H. oregonensis is combined with low salinity, but smallest smooth), its frontal margin is straight and it

Hiebert, T.C. 2015. Hemigrapsus nudus. 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. specimens are most resistant to temperature and the production of second brood is rare. extremes (Todd and Dehnel 1960). Embryos are approximately 380 µm in Tidal Level: Strictly littoral (Ricketts and diameter and become 450 µm upon hatching Calvin 1971) and found higher than H. (Jaffe et al. 1987). The reproduction and life- oregonensis, but both species are found from cycle of C. epialti is dependent on and high to low levels (Todd and Dehnel 1960). corresponds to that of its host species. Occurs is the rockweed belt, underneath However, this nemertean is not host specific rocks and is commonly found just below high- (unlike Carcinonemertes errans on Cancer tide level (Monterey, California, Hiatt 1948). magister) and occurs amongst egg masses of Hemigrapsus nudus is often found with other species including Hemigrapsus Pachygrapsus, which extends higher into the oregonensis, Pachygrapsus crassipes (Kuris intertidal and prefers larger rocks. 1993; Roe et al. 2007; Kuris et al. 2007). Associates: Territory overlaps with Larva: Larval development in H. nudus Pachygrapsus crassipes over whom it is proceeds via a series of zoea (five total) and dominant (Hiatt 1948) and occasionally with megalopa stages, each marked by a molt. H. oregonensis. Parasitic castrating isopod, The zoea are planktotrophic and have large Portunion conformis, occurs in perivisceral compound eyes and four spines: one each cavity of some individuals (Garth and Abbott dorsal and rostral and two lateral (see Fig. 32, 1980). Can be host to nemertean Puls 2001; Fig. 54.5, Martin 2014). The Carcinonemertes epialti. Hemigrapsus rostrum and dorsal spines are of equal length nudus, H. oregonensis and P. crassipes can and the two lateral spines are shorter (Puls all be host to this nemertean egg predator, 2001). The first zoea has exospines on the which can negatively impact brood mortality in telson, is approximately 1.2 mm (measured these species (Shields and Kuris 1988). from tip of rostrum to tip of telson) and has These three species can also serve as lateral knobs on the second and third intermediate hosts for a variety of parasites segments, where H. oregonensis has lateral including trematode metacercariae, larval knobs on only the second segment (Puls trypanorhynch tapeworms, as well as 2001). The larvae of H. nudus are also a bit Polymorphus acanthocephalan and nematode larger and more robust than those of closely (Ascarophis) larvae (Kuris et al. 2007). related H. oregonensis (Jaffe et al. 1987). Abundance: Locally abundant (Ricketts and The zoea of Hemigrapsus species and P. Calvin 1971) and less common south (e.g. crassipes can be differentiated by body and Morrow Bay, California, Kuris et al. 2007). eye size (Schlotterbeck 1976). Hemigrapsus nudus megalopae are rectangular and can be Life-History Information recognized by a posterior telson with setae Reproduction: In Puget Sound, Washington, (other than uropod setae) and a carapace that mating occurs between December and is 1.8 mm in length and 1.5 mm in width (Puls January and is similar to Pachygrapsus (Hiatt 2001). 1948; see Fig. 2, 3, Knudsen 1964), however Juvenile: A shallow depression is present P. crassipes exhibits peak breeding in along the frontal area, notches and lateral summer months compared to winter months spines are not terribly sharp or clearly in H. nudus (Boolootian et al. 1959). Females separated from the side. Eyes are large (Fig. ovigerous January through April, 70% 3) and dactyls are short with the dactyl of leg ovigerous in late January and 99% with four quite flat (Carlton and Kuris 1975). fertilized eggs early April. Hatching occurs Juveniles of both sexes with narrow between May and June (Puget Sound, abdomens. Washington). This timeline can be earlier Longevity: (hatching Oct–May in Monterey Bay, Growth Rate: Growth occurs in conjunction California) or later (ovigerous April–May, with molting. In pre-molting periods the British Columbia, Canada and hatching July, epidermis separates from the old cuticle and Friday Harbor, Washington) (Jaffe et al. 1987; a dramatic increase in epidermal cell growth Puls 2001) depending on water temperature. occurs. Post-molt individuals will have soft Each brood contains 400–36,000 embryos shells until a thin membranous layer is

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12710 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to [email protected] deposited and the cuticle gradually California. R. H. Morris, D. P. Abbott, hardens. During a molt decapods have the and E. C. Haderlie (eds.). Stanford ability to regenerate limbs that were University Press, Stanford, CA. previously autotomized (Kuris et al. 2007). 5. HIATT, R. W. 1948. The biology of the Food: An herbivore and detritivore that lined shore crab Pachygrapsus ingests algae infrequently (Kozloff 1993). crassipes Randall. Pacific Science. Individuals forage in large numbers on the 2:135-213. tops of rocks and stomach contents reveal 6. KNUDSEN, J. W. 1964. Observations amphipods and other crustaceans provide a of the reproductive cycles and ecology small part of the diet (Knudsen 1964). of the common Brachyura and crablike Predators: Fish, raccoons and probably blue Anomura of Puget Sound, herons. Also predated by Pachygrapsus (on Washington. Pacific Science. 18:3-33. newly molted animals). 7. KOZLOFF, E. N. 1993. Seashore life Behavior: Although shore crabs are of the northern Pacific coast: an generally believed to be fast moving illustrated guide to northern California, (Wicksten 2011), H. nudus is rather sluggish Oregon, Washington, and British and sometimes feigns death when disturbed Columbia. University of Washington (Hiatt 1948; Kuris et al. 2007). Hemigrapsus Press, Seattle, WA. nudus is a nocturnal feeder (Garth and Abbott 8. KURIS, A. M. 1993. Life cycles of 1980) and males are more aggressive than nemerteans that are symbiotic egg females, fighting when attacked. Females, on predators of decapod crustacea: the other hand, autotomize easily in order to adaptations to host life histories. escape (Knudsen 1964). Hydrobiologia. 266:1-14. 9. KURIS, A. M., P. S. SADEGHIAN, J. Bibliography T. CARLTON, AND E. CAMPOS. 2007. Decapoda, p. 632-656. In: The 1. BOOLOOTIAN, R. A., A. C. GIESE, A. Light and Smith manual: intertidal FARMANFAMAIAN, AND J. TUCKER. invertebrates from central California to 1959. Reproductive cycles of five west Oregon. J. T. Carlton (ed.). University coast crabs. Physiological Zoology. of California Press, Berkeley, CA. 32:213-220. 10. MARTIN, J. W. 2014. Brachyura, p. 2. CARLTON, J. T., AND A. M. KURIS. 295-310. In: Atlas of crustacean 1975. Keys to decapod crustacea, p. larvae. J. W. Martin, J. Olesen, and J. 385-412. In: Light's manual: intertidal T. Høeg (eds.). Johns Hopkins invertebrates of the central California University Press, Baltimore, MD. coast. S. F. Light, R. I. Smith, and J. T. 11. MCGAW, I. J. 2003. Behavioral Carlton (eds.). University of California thermoregulation in Hemigrapsus Press, Berkeley. nudus, the amphibious purple shore 3. DE GRAVE, S., N. D. PENTCHEFF, crab. Biological Bulletin. 204:38-49. S. T. AHYONG, T. CHAN, K. A. 12. NG, P. K. L., D. GUINOT, AND P. J. F. CRANDALL, P. C. DWORSCHAK, D. DAVIE. 2008. Systema brachyurorum: L. FELDER, R. M. FELDMANN, C. Part I. Annotated checklist of the FRANSEN, L. Y. D. GOULDING, R. extant Brachyuran crabs of the world. LEMAITRE, M. E. Y. LOW, J. W. Raffles Bulletin of Zoology MARTIN, P. K. L. NG, C. E. Supplement. 17:1-286. SCHWEITZER, S. H. TAN, D. 13. NYBLADE, C. F. 1987. Phylum or TSHUDY, AND R. WETZER. 2009. A Subphylum Crustacea, Class classification of living and fossil Malacostraca, Order Decapoda, genera of decapod crustaceans. Anomura, p. 441-450. In: Raffles Bulletin of Zoology:1-109. Reproduction and development of 4. GARTH, J. S., AND D. P. ABBOTT. marine invertebrates of the northern 1980. Brachyura: The true crabs, p. Pacific coast. M. F. Strathmann (ed.). 594-630. In: Intertidal invertebrates of