Americorophium Spinicorne Class: Malacostraca Order: Amphipoda, Gammaridea Family: Corophiiadae

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Phylum: Arthropoda, Crustacea Americorophium spinicorne Class: Malacostraca Order: Amphipoda, Gammaridea Family: Corophiiadae

Taxonomy: Corophium spinicorne was Eyes: among the first corophiid amphipods Antenna 1: Reaching to the middle of described in North America by Stimpson the fifth segment of the second antenna. 1857. It was transferred to the genus Flagellum with 11 (female) or 14–16 joints Americorophium in 1997 based on (male). Female may have one to three spines morphological characters (Bousfield and on the first and second peduncular joints (Fig. Hoover 1997) (see Possible 5). Misidentifications). Not all researchers have Antenna 2: Long as or longer than followed this transition in other body in males. Fourth joint with large distal Americorophium species (e.g. Lester and half-moon tooth and no small accessory Clark 2002; Sakamaki and Richardson 2009), tooth. Fifth joint with distal spine and but we follow the nomenclature used in other proximal spine, which is well within tooth current local intertidal guides (Chapman when joint is flexed (Fig. 1). Females have 2007). similar toothed fourth joint (Fig. 5), with spines also on the fifth joint. The fifth joint has a Description proximal spine that opposes the large half- Size: Largest species of Americorophium on moon tooth when the joint is flexed. Both the west coast with females 8–10 mm, in sexes have prominent gland cones on the length (South Slough of Coos Bay) and males second article (Figs. 1, 5), but that of the 6 mm in length (Shoemaker 1949). female is acute and curves forward sharply Color: Clear, with dark brown markings on (Fig. 5). antennae and thoracic segments. Mouthparts: General Morphology: The body of Pereon: amphipod crustaceans can be divided into Coxae: Setose lamellae (pairs of three major regions. The cephalon (head) brood plates attached to bases of coxae) (Fig. includes antennules, antennae, mandibles, 6) are present in females only. Do not maxillae and maxillipeds (collectively the confuse with fleshy gills that are present on mouthparts). Posterior to the cephalon is the both sexes. pereon (thorax) with seven pairs of Gnathopod 1: pereopods attached to pereonites followed by Gnathopod 2: Filtering type, with fine the pleon (abdomen) with six segments long setae, present in both sexes, comprising three pleonites (together the morphology as in other Americorophium pleosome), three urosomites (together the species. urosome), and finally a telson at the animal Pereopods 3 through 7: posterior (see Plate 254, Chapman 2007). In Pleon: members of the genus Americorophium, the Pleonites: body is flattened dorso-ventrally and rarely Urosomites: Urosome and third exceeds 1 cm in total length (including uropod morphology as in other antennae) in local specimens (see Fig 46, Americorophium species (see A. brevis, Figs. Kozloff 1993). 3, 4). Cephalon: Epimera: Rostrum: Rounded in both sexes Telson: (Fig. 3b, 4), but male rostra are sometimes Sexual Dimorphism: Sexes share a more straight (Fig. 3a) (Shoemaker 1949). similar morphology,than other Americorophium species.

Possible Misidentifications fourth article of the second antenna, but The gammarid family Corophiidae is without the small accessory tooth. characterized by individuals that build U- Americorophium spinicorne is also strongly shaped tubes in both soft sediments and on euryhaline and often found in fresh-water hard surfaces, sometimes forming dense habitats. Segments of urosome are aggregations. Species can be dramatically separate and no fused in A. spinicorne and sexually dimorphic and and, although males males and females can be distinguished by may be easier to identify with taxonomically the second antennal features (see Antenna relevant characters including the rostrum 2) and by the presence of lamellae and/or and peduncle of second antennae, most eggs in females. females can be reliably identified to species Males: Of the Americorophium as well (Chapman 2007). Five corophiid species in which males have urosome genera occur locally, Americorophium, segments dissimilar to females, A. Corophium, Crassicorophium, stimpsoni, A. brevis, and A. salmonis all Laticorophium and Monocorophium. The have a half-moon and accessory tooth on three common estuarine species in this the fourth article of the second antenna. guide (A. brevis, A. salmonis, A. spinicorne) Americorophium brevis and A. salmonis were previously members of the genus often have similar rostrums, but that of A. Corophium (see Shoemaker 1949), but stimpsoni has a prominent central lobe were transferred to the genus nearly as long as the ocular lobes. In A. Americorophium in 1997 (Bousfield and salmonis the first antenna reaches only to Hoover 1997). the middle of the fourth article. All Americorophium species have Americorophium brevis does not have the filtering-type second gnathopods and long flat expanded first articles of the first setae on the third uropods. Of the four local antenna and A. salmonis usually has 14–16 Americorophium species, sexual articles in the flagellum, (though occasional dimorphism is strong in the three species A. specimens will have 11–12). In A. brevis, brevis, A. salmonis, and A. stimpsoni. In the males have about 11 articles in the particular, the second antenna and fourth flagellum of the first antenna. The uropods segment differ between males and females of A. salmonis and A. brevis are quite (Shoemaker 1949). This is not the case, dissimilar. In A. salmonis, the peduncle of however, for the fourth Americorophium the first uropod is armed on the outside species, A. spinicorne, where male and edge with three to six long, slender spines female morphologies are similar. Additional and at the distal edge with two to three characteristics that differ between species short, blunt spines. Americorophium brevis (particularly A. brevis and A. salmonis) has instead only eight short, blunt spines. include first antenna, telson, first uropods The third uropods of A. salmonis have many and third uropods. more and longer setae than those of A. Americorophium stimpsoni, brevis. The telson shape and spination of principally a northern California species, the two species are also quite different does not seem to occur in Oregon. Its chief (compare Figs. 4, A. brevis, and Fig. 5, A. key characteristic is a prominent male salmonis in this guide). rostrum, almost as long as the ocular lobes. Females: A. salmonis and A. The females are much like those of A. stimpsoni females are very much alike, salmonis. with no strong distinguishing Americorophium spinicorne, another characteristics, so the species should not prominent northwest species, has less be differentiated solely by female sexual dimorphism that other specimens. The only Americorophium Americorophium species. Both males and female of this group to have the half-moon females have a half-moon tooth on the hook is A. spinicorne, so this species is

Hiebert, T.C. 2015. Americorophium spinicorne. 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. easily distinguished from others. of the San Joaquin river estuary (Aldrich Americorophium brevis has three pairs of 1961). spines, as well as a spine on the gland cone, instead of having two single spines Life-History Information on the underside of the fourth article of the Reproduction: Development in most second antenna. The first antenna has amphipods is direct, lacking a larval stage, eight joints in the flagellum, while that of A. and little is known about the reproduction and salmonis has ten. development in A. spinicorne. Ovigerous females have been observed in February, Ecological Information March, May and December (Eriksen 1968). Range: Type locality is San Francisco, In the European species, Corophium California (Bousfield and Hoover 1997). volulator, breeding occurs in February (over- Known range includes estuaries and brackish wintering population) and again in July– waters from Santa Cruz, California to Alaska August. Young remain in brood pouch four (Chapman 2007). Additionally, A. spinicorne weeks and females produce up to four broods has been reported from two locations along per year (Green 1968). the Snake River in Idaho (Lester and Clark Larva: Since most amphipods develop 2002). directly, they lack a definite larval stage. Local Distribution: Oregon estuaries and Instead the young developmental stage lakes including South Slough of Coos Bay, resembles small adults (e.g. Fig. 39.1, Wolff Tillamook Bay and Floras Lake. 2014). Habitat: Members of the Corophiidae inhabit Juvenile: small U-shaped tubes in soft sediments, or on Longevity: hard surfaces (Chapman 2007). Muddy Growth Rate: Amphipod growth occurs in substrates as well as sandy beaches conjunction with molting where the (Barnard 1954), gravel and clay (Aldrich exoskeleton is shed and replaced. Post-molt 1961). Individuals occur in areas of heavy individual will have soft shells as the cuticle silting (Kozloff 1993), but prefers sand gradually hardens (Ruppert et al. 2004). (Eriksen 1968). Comparisons of macrofaunal Food: A detritovore, ingesting particulate communities within and outside of Dendraster organic matter (Sakamaki and Richardson excentricus beds found Americorophium 2009), A. spinicorne sorts material with species to be more prevalent where sand filtering gnathopods. Abdominal appendages dollars were not present (Smith 1981). create a water current that is filtered by the Corophiid amphipods are frequently used in fine hairs on the gnathopods, and the filtrate tests of sediment toxicity and/or water quality is then scraped off and ingested (Miller 1984; (e.g. fluoranthene, Swartz et al. 1990). Kozloff 1993). Salinity: Brackish to freshwater where Predators: The tidewater goby, Eucyclogius salinities range from 0.02–33.6 (Eriksen newberryi (Swenson and McCray 1996), 1968). young Chinook salmon (Forsberg et al. 1977; Temperature: 10–22.8°C (Eriksen 1968). Busby and Barnhart 1995) and white sturgeon Tidal Level: (Acipenser transmontanus, McCabe et al. Associates: 1993) all feed on A. spinicorne. Avery and Abundance: Populations often very dense Hawkinson (1992) also found that grey whale and easily observed or collected in the field. populations exhibited greater feeding activity The abundance of Americorophium species in areas with high density of corophid tube was measured in the Campbell River Estuary mats and dominated by the species A. and ranged from zero to ~15,000–31,000 per spinicorne, in northern California. square meter in July (Raymond et al. 1985). Behavior: Abundances in excess of 100 individuals per square meter have also been documented Bibliography (Eriksen 1968). Americorophium spinicorne is the dominant invertebrate in the river bottom 1. ALDRICH, F. A. 1961. Seasonal variations in the benthic invertebrate

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12689 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] fauna of the San Joaquin River Columbia. University of Washington Estuary of California, with emphasis Press, Seattle, WA. on the amphipod, Corophium 11. LESTER, G. T., and W. H. CLARK. spinicorne (Stimpson). Proceedings of 2002. Occurrence of Corophium the Academy of Natural Sciences of spinicorne (Stimpson, 1857) Philadelphia. 113:21-28. (Amphipoda: Corophiidae) in Idaho, 2. AVERY, W. E., and C. HAWKINSON. USA. Western North American 1992. Gray whale feeding in a Naturalist. 62:230-233. northern California estuary. Northwest 12. MCCABE, G. T., R. L. EMMETT, and Science. 66:199-203. S. A. HINTON. 1993. Feeding ecology 3. BARNARD, J. L. 1954. Marine of juvenile white sturgeon Nacipenser amphipoda of Oregon. Allan Hancock transmontanus in the lower Columbia Foundation for Scientific Research. River. Northwest Science. 67:170-180. Contribution. 102. 13. MILLER, D. C. 1984. Mechanical post- 4. BOUSFIELD, E. L., and P. M. capture particle selection by HOOVER. 1997. The amphipod suspension feeding and deposit superfamily Corophioidea on the feeding Corophium. Journal of Pacific coast of North America. Part 5. Experimental Marine Biology and Family Corophiidae: Corophiinae, new Ecology. 82:59-76. subfamily. Systematics and 14. RAYMOND, B. A., M. M. WAYNE, and distributional ecology. Amphipacifica. J. A. MORRISON. 1985. Vegetation, 2:67-139. invertebrate distribution, and fish 5. BUSBY, M. S., and R. A. BARNHART. utilization of the Campbell River 1995. Potential food sources and Estuary, British Columbia, Canada. feeding ecology of juvenile fall chinook Canadian Manuscript Report of salmon in California's Mattole River Fisheries and Aquatic Sciences: 1-33. Lagoon. California Fish and Game. 15. RUPPERT, E.E., R.S. FOX, and R.D 81:133-146. BARNES. 2004. Invertebrate 6. CHAPMAN, J. W. 2007. Amphipoda: zoology: a functional evolutionary Gammaridea, p. 545-611. In: The approach, 7th Edition. Thomson Light and Smith manual: intertidal Brooks/Cole, Belmont, CA. invertebrates from central California to 16. SAKAMAKI, T., and J. S. Oregon. J. T. Carlton (ed.). University RICHARDSON. 2009. Dietary of California Press, Berkeley, CA. responses of tidal flat macrobenthos to 7. ERIKSEN, C. H. 1968. Aspects of the reduction of benthic microalgae: a test limno-ecology of Corophium for potential use of allochthonous spinicorne (Stimpson) (Amphipoda) organic matter. Marine Ecology and Gnorimosphaeroma oregonensis Progress Series. 386:107-113. (Dana) (Isopoda). Crustaceana. 14:1- 17. SHOEMAKER, C. R. 1949. The 12. amphipod genus Corophium on the 8. FORSBERG, B. O., J. A. JOHNSON, west coast of America. Journal of the and S. I. KLUG. 1977. Identification, Washington Academy of Sciences. distribution and notes on food habits of 89:66-82. fish and shellfish in Tillamook Bay, 18. SMITH, A. L. 1981. Comparison of Oregon. Oregon Department of Fish macrofaunal invertebrates in sand and Wildlife, s.l. dollar (Dendraster excentricus) beds 9. GREEN, J. 1968. The Biology of and in adjacent areas free of sand estuarine animals. University of dollars. Marine Biology. 65:191-198. Washington Press, Seattle. 19. SWARTZ, R. C., D. W. SCHULTS, T. 10. KOZLOFF, E. N. 1993. Seashore life H. DEWITT, G. R. DITSWORTH, and of the northern Pacific coast: an J. O. LAMBERSON. 1990. Toxicity of illustrated guide to northern California, fluoranthene in sediment to marine Oregon, Washington, and British amphipods: a test of the equilibrium