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Phylum: Arthropoda, Crustacea Eohaustorius estuarius Subphylum: Malacostraca Order: Amphipoda, Gammaridea A sand-burrowing amphipod Family: Haustoriidae Description Pereon: Size: Holotype is a female from Yaquina Bay, Coxae: Coxal plates one and two Oregon that is 4 mm in length. Paratypes are small and hidden beneath three and four (Fig. 2.0–4.5 mm in length (measured from the 1). Coxal margins rounded and not pointed. distal anterior end to the posterior telson) Gnathopod 1: Small, feeble and (Bosworth 1973). The illustrated specimens, simple with article five longer than six (Kozloff collected from the lower Columbia River, were 1987) (Fig. 1). up to 6 mm long (Fig. 1). Gnathopod 2: Feeble, small and Color: White, in life and in preservation minutely chelate (Barnard 1969) (Fig. 5). (Bosworth 1973). Pereopods 3 through 7: Pereopods General Morphology: The body of lack dactyls (i.e. have only six articles), are amphipod crustaceans can be divided into furry and fringed with long bristles three major regions. The cephalon (head) or (Eohaustorius, Kozloff 1987). Pereopod four cephalothorax includes antennules, antennae, is smaller than pereopod three and is mandibles, maxillae and maxillipeds reversed and positioned like pereopods 5–7, (collectively the mouthparts). Posterior to not like 1–3 (Barnard 1969; 1975) (Fig. 1). the cephalon is the pereon (thorax) with Pereopod five with only one fascicle (bundle) seven pairs of pereopods attached to of spines on posterior edge of article six and pereonites followed by the pleon (abdomen) with articles five and six relatively equal in with six pairs of pleopods. The first three sets length (Bosworth 1973) (Fig. 1). Pereopod of pleopods are generally used for swimming, six like pereopod seven in length and general while the last three are simpler and surround shape (i.e. not excessively long, Barnard the telson at the animal posterior. The 1975). Pereopod seven with posterior dorsal amphipod family Haustoriidae are abundant in corner of article two smoothly rounded, clean, fine sand in estuaries or marine without a cusp (arrow, Fig. 1) and with article habitats were they swim and burrow upside- five having two fascicles of spines on its down (Chapman 2007). anterior edge (Fig. 1). Cephalon: Pleon: Rostrum: Short, visor-like and Pleonites: Third pleonites with a fine pointed (Fig. 2). posterior fringe (Fig. 1). Eyes: Visible in live specimens (not Urosomites: Segments two and once preserved). Bright white in anterior three not fused, but freely articulated (Kozloff distal corners of head (Bosworth 1973). 1987). Urosomites small and hidden beneath Ovoid in shape, with irregular indentations, pleonites (Figs. 1, 6). Third uropods each not protruding above the surface. Eyes with two rami of equal length (Barnard 1969) probably not compound (Fig. 2). (Fig. 7). Antenna 1: Massive, setose and not Epimera: geniculate (i.e. bent like a knee) (Fig. 2). Telson: Thin, flattened, setose lobes that are Antenna 2: Peduncle articles large widely separated at bases by urosomites and flat, very setose and with multiarticuate (Haustoriidae, Barnard 1975) (Fig. 6). accessory flagellum (Fig. 3). Sexual Dimorphism: No obvious differences Mouthparts: Mandible with palp and between males and females (Bosworth 1973). always consisting of three articles (Haustoriidae, Barnard 1969). Palp with smooth molar (Fig. 4). Hiebert, T.C. 2015. Eohaustorius estuaris. 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/1794/12707 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Possible Misidentifications washingtonianus. Described from Puget The Phoxocephalidae and Sound, it has also been found in Coos Bay, Haustoriidae are morphologically similar Yaquina Bay, and in the lower Columbia gammarid amphipod families. Unlike the River. This species can be larger than E. latter, Phoxocephalidae have very dissimilar estuarius, to 8 mm long (Kozloff 1993). It has pereopods six and seven: six is long and a prominent crescent-shaped cusp on the seven has a broad second article (see dorsal posterior edge of article two of Eobrolgus spinosus). In the phoxocephalids, pereopod seven and there are three fascicles the fourth pereopod is not reversed as in the of spines on the posterior edge of article six, Haustoriidae, and although the rostrum is pereopod five. In the Newport area (e.g. visor-like, it is much longer. Yaquina Bay), it overlaps with E. brevicuspis The Haustoriidae have feeble intertidally, and with E. sawyeri subtidally, gnathopods, a mandible with a 3-articled palp, being found from -0.76 to +1.22 meters and spinose and setose pereopods. There (Bosworth 1973). Eohaustorius sencillus has are many genera in the family, but a first gnathopod with a sixth article that is Eohaustorius is the only genus in which all swollen and has an apical spine. The the pereopods (3–7) lack dactyls (Barnard seventh article on gnathopod one is quite 1969). It is also the only genus of the family long. This species lacks the cusp on article found in (and restricted to) the northern two of pereopod seven (as does E. estuarius). Pacific (Barnard 1969), where there are six Eohaustorius sencillus is found commonly species (Chapman 2007). from Monterey Bay, California (Barnard 1962) Eohaustorius is the only genus in the to southern California. Eohaustorius barnardi family Haustoriidae that occurs exclusively on is a subtidal species that occurs in fine sand, Pacific coasts (from Russia to Mexico, and is 5 mm in length (Chapman 2007). Slattery 1985; Bousfield and Hoover 1995). Six species in the genus have been found in Ecological Information Oregon and four were described by Bosworth Range: Type locality is Yaquina Bay, OR in 1973 (Eohaustorius brevicuspis, E. sawyeri, (Bosworth 1973) and known range includes E. washingtonianus and E. estuarius). the entire northeastern Pacific (Chapman Eohaustorius brevicuspis and E. sawyeri 2007). inhabit only the open coast (Bosworth 1973). Local Distribution: Local distribution at Eohaustorius brevicuspis was described from several Coos Bay sites, including the North Lost Creek Beach, south of Newport, Oregon Bend Airport extension site. Additional sites (Bosworth 1973). It has a small cusp on the in Oregon include Yaquina Bay (near the dorsal posterior margin of article two of Hatfield Marine Science Center) and lower pereopod seven and it has only two fascicles Columbia River. of spines on the posterior edge of article six Habitat: Burrows in relatively clean, medium or pereopod seven. This species is found sized sand with a fairly high proportion of high in the intertidal, from +0.6 to 3.6 meters organic material. An estuarine species, it is MLLW, and never in brackish water (Bosworth found on open coast only where there is 1973). Eohaustorius sawyeri, often found freshwater runoff (Bosworth 1973). with E. brevicuspis, lacks the cusp on the Eohaustorius estuarius is a common species seventh pereopod and has instead a bulge on used in toxicity testing (e.g. Kohn et al. 1994; the posterior edge of the second article (of the Kravitz et al. 1999; Hecht and Boese 2002; seventh pereopod). The posterior edge of the Kuo et al. 2010; Greenstein et al. 2013; Ernst sixth article of pereopod seven has four et al. 2014). It is the primary species used in fascicles of spines. This species is subtidal, the San Francisco Bay Estuary Regional marine and found from MLLW down to -0.76 Monitoring Program where it has been tested meters. It has not been found in estuarine for sensitivity to a wide variety of toxins conditions (Bosworth 1973). The species including copper, fluoranthene, chlorpyrifos, most likely to be confused with E. estuarius, permethrin, bifenthrin and cypermethrin, the and which is also found occasionally in the latter four toxins eliciting the most sensitive more marine portions of estuaries, is E. response (Anderson et al. 2008). Hiebert, T.C. 2015. Eohaustorius estuaris. 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. Eohaustorius estuarius also exhibited a Longevity: The longevity of E. estuarius is dramatic, short-term population decline not directly known, but local species in the following exposure to carbaryl, an oyster families Haustoriidae (e.g. E. sencillus) and farming pesticide (Dumbauld et al. 2001). Phoxocephalidae (e.g. Rhepoxynius fatigans, Salinity: Brackish water (e.g. salinity at type R. abronius) are on an annual cycle (Slattery locality ranges from 1–25). 1985). Temperature: Growth Rate: Amphipod growth occurs in Tidal Level: Intertidal and subtidal (up to 7 conjunction with molting where the meters deep, Bosworth 1973; Chapman exoskeleton is shed and replaced. Post-molt 2007). Some small permanent populations individuals will have soft shells as the cuticle occur in high intertidal if freshwater stream gradually hardens (Ruppert et al. 2004). runoff occurs (Bosworth 1973). Food: Associates: Does not overlap with habitats Predators: Fish, shorebirds. of other Oregon Eohaustorius species, where Behavior: Phoxocephalid and haustoriid E. estuarius is found in brackish water, E. species tend to be very mobile and efficient brevicuspis occurs mid-intertidally and E. burrowers (Slattery 1985) and E. estuarius is washingtonianus and E. sawyeri are found in a strong digger, with an impressive armament the lower intertidal (Bosworth 1973). of spines and setae used for digging. Abundance: Densest at intertidal heights (Bosworth 1973). Bibliography Life-History Information 1. ANDERSON, B. S., S. LOWE, B. M. Reproduction: Most amphipods have PHILLIPS, J. W. HUNT, J. VORHEES, separate sexes with some sex determination S. CLARK, and R. S. TJEERDEMA.

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