Eogammarus Confervicolus Class: Malacostraca Order: Amphipoda, Gammaridea Family: Anisogammaridae

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Phylum: Arthropoda, Crustacea Eogammarus confervicolus Class: Malacostraca Order: Amphipoda, Gammaridea Family: Anisogammaridae

Taxonomy: Originally described as Maera second antenna and with posterodistal spine confervicolus, E. confervicolus has undergone on peduncle (Fig. 1) (Eogammarus, Bousfield various generic designations including 1979). Posterodistal setae on article one Gammarus and, most recently, spiniform (Tomikawa et al. 2006). Anisogammarus. In 1979, Bousfield revised Antenna 2: Stout, shorter than first the family Anisogammaridae and promoted and with 14 articles (Fig. 1). Peduncles four Eogammarus to generic rank comprising 10 and five with two (rarely three) posterior species (including E. confervicolus, Tomikawa marginal groups of setae (in addition to et al. 2006). Species within this genus remain terminal group) (Bousfield 1979; Tomikawa et difficult to identify, however, because original al. 2006). descriptions often lack sufficient detail. Mouthparts: Mandible with palp, molar large and bears rasping surface. No Description palp setae on the first article of maxilla one Size: Individuals up to 19 mm. Male (Tomikawa et al. 2006). specimens range locally from 12 mm (South Pereon: Slough of Coos Bay) to 16 mm in length Coxae: First four coxal plates (Siuslaw Estuary). become gradually larger and the fourth is Color: White with dark brown mottling and rounded (Fig. 1) while plates 5–7 are quite brown stripes on the first and second small. antennae. Gnathopod 1: Slightly smaller than General Morphology: The body of second gnathopod. Article six with palm amphipod crustaceans can be divided into oblique, nine peg-like teeth and dactyl curved three major regions. The cephalon (head) or (Fig. 2a). cephalothorax includes antennules, antennae, Gnathopod 2: Much like the first mandibles, maxillae and maxillipeds gnathopod, but larger and palm with seven (collectively the mouthparts). Posterior to stout pegs (Fig. 2b). the cephalon is the pereon (thorax) with Pereopods 3 through 7: Strong, seven pairs of pereopods attached to becoming larger posteriorly and spinous but pereonites followed by the pleon (abdomen) without plumose setae on margins of basis with six pairs of pleopods. The first three sets and carpus (Tomikawa et al. 2006). of pleopods are generally used for swimming, Pleon: while the last three are simpler and surround Pleonites: No dorsal spines and only the telson at the animal posterior. Amphipods 0–2 posterior marginal setae (Fig. 1). in the Gammaroidea (including Gammaridae Urosomites: Urosome one with four and Anisogammaridae) display weak sexual dorsal groups of three spines each. Urosome dimorphism (Chapman 2007). (For detailed two with dorsal spines in two groups and no key and description of E. confervicolus see prominent median tooth (Fig. 3) (key Figs. 14–17 Tomikawa et al. 2006). taxonomic character, Bousfield 1979). Cephalon: Uropods one and two with 2–4 groups of Rostrum: Rostrum vestigial. spines. Uropod two with rami extending Eyes: beyond peduncle of uropod three (Fig. 1) Antenna 1: Almost equal to ½ body (Bousfield 1979). The inner margin of the length and with an accessory flagellum of five outer ramus in uropod three usually with four articles (Fig. 1). Longer than (or equal to) groups of strong spines, but less than 10 isolated plumose setae. The inner ramus is

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12706 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] less than ½ length outer ramus (Fig. 4) marginal setae (Bousfield 1979). The only (Bousfield 1979). other species of Eogammarus in the Epimera: northeastern Pacific region is Eogammarus Telson: Split, with connected lobes each with oclairi, a pelagic estuarine form very like E. two spines, and only one spine is apical (at confervicolus. Both have robust setae on the tip) (Fig. 3). Eogammarus confervicolus article one of antenna two and no marginal and E. oclairi can be differentiated by telson setae on the palp of article one on maxilla characters, as the latter species only has one one. They can be differentiated by each spine on each lobe. However, it is currently telson lobe, which has two terminal setae, in unclear whether this feature is representative E. oclairi, not one as in E. confervicolus of two species, or if E. oclairi is simply large (Bousfield 1979). Additional characters E. confervicolus (Bousfield 1979; Chapman include the following (see Tomikawa et al. 2007). 2006): aesthetasc of flagellum on antenna Sexual Dimorphism: Sexual dimorphism is one is equal to setae in E. confervicolus and relatively weak among the Gammaroidea longer in E. oclairi; female calceoli on compared to other amphipod families. antenna two are absent in the former species Female and male E. confervicolus differ very and present in the latter; the longest setae little, if at all. Females can be smaller, have on pereopod six is half the width of the smaller gnathopods, and shorter antenna ischium in the former and shorter in the latter than do the males. species; and the robust telson setae are equal to or shorter than the slender setae in Possible Misidentifications E. confervicolus, but longer in E. oclairi Gammaroidea comprises the two amphipod (Tomikawa et al. 2006). Despite these families Anisogammaridae and Gammaridae. characters, it remains a possibility that E. The Gammaridae is characterized by confervicolus and E. oclairi are the same gnathopods of dissimilar size (males), palms species and the above variations are simply oblique and with simple spines and slender due to individual size (Chapman 2007). simple dactyls. They also have simple coxal Members of the closely related genus gills without accessory lobes and urosome Anisogammarus have first antenna shorter segments with posterodorsal spines in groups than the second (the most distinctive of three (Bousfield 1979). The character) (Bousfield 1979). In Anisogammaridae, on the other hand, have Anisogammarus, each of the urosomites has gnathopods that are morphologically a prominent median tooth and a smaller pair subsimilar, have palms with margins vertical of dorsolateral teeth, not 2–4 groups of and lined with blunt spines and massive spines as in Eogammarus. Finally, on dactyls with posterior accessory blades. They uropod three, the rami are subequal, not also have coxal gills with accessory lobes and disparate in size as in Eogammarus. urosome segments with posterodorsal spines Anisogammarus pugettensis has a in clusters of two or four (Bousfield 1979, prominent fixed median spine on its second 2001). The Gammaridae includes three urosomite and no rows of spines (Bousfield species in the genus Gammarus locally, none 2001). of which are certain to be native (Chapman Another closely related genus is 2007). The Anisogammaridae includes seven Ramellogammarus, characterized by dorsal local species including one in the genus groups of spines on its pleon segments: Anisogammarus, four in the genus groups of 1–3 on urosomes one and two; Ramellogammarus and two in Eogammarus urosome three with 1–2 posterodorsal (Chapman 2007). groups of spines; and 1–4 groups of The genus Eogammarus is posterior marginal setae on peduncle characterized by uropods one and two with segments of both first and second antennae rami linear and with apical margins spinose, (Bousfield 1979; Bousfield and Morino 1992; urosome segments one and two with 2–4 Chapman 2007). Ramellogammarus groups of spines and peduncular segments oregonensis and R. ramellus were both one and two with 2–3 groups of posterior previously members of Gammarus,

Hiebert, T.C. 2015. Eogammarus confervicolus. 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. Anisogammarus and Eogammarus. increase rapidly, as was found in Suisun Ramellogammarus oregonensis is strongly Marsh, California, where E. confervicolus armed on pleonites 1–3, while R. ramellus were introduced to a wetland pond in has a single posterior seta on pleon plate September and became a numerically three (Bousfield and Morino 1992). The two dominant member of the pond by February other species in the genus (Batzer and Resh 1992). Ramellogammarus are freshwater species, R. columbianus, and R. littoralis (Chapman Life-History Information 2007). Reproduction: Most amphipods have Ecological Information separate sexes with some sex determination Range: Type locality is in California correlated with environmental conditions (Tomikawa et al. 2006), but specific locale (Straude 1987). Females brood embryos in was not found. Known range includes San an external thoracic brood chamber and Diego, California to Alaska. irrigate embryos with a flow of water produced Local Distribution: Local distribution by pleopod movement. Development within includes sites in South Slough (e.g. Salicornia this brood chamber is direct and individuals marsh and Metcalf Preserve). Also occurs on hatch as juveniles that resemble small adults, log booms and in mud (e.g. South Slough, with no larval stage. The reproduction and Siltcoos River, Siuslaw Estuary) (Barnard development of E. confervicolus was 1954). described by Rappaport (1960). Habitat: Muddy substrates. Eogammarus Reproductive behavior and coupling occurs confervicolus gets name from the "conferva" nine days prior to mating. Females are or long green algae on which it lives. Also ovigerous from October to December and, occurs with Salicornia, Carex and Fucus again, from June to August (Bousfield 1979). (Straude 1987). Growth of E. confervicolus Brood size ranges from 10 to 75 embryos and was compared between three habitats and duration within the brood is 17 days at 10˚C ranked as follows: highest in an embankment and a salinity of 15 (Straude 1987). along the perimeter of a marsh, medium Larva: Since most amphipods are direct along the edge of a Fucus community and developing, they lack a definite larval stage. lowest in habitat dominated by woody debris Instead this young developmental stage (Stanhope and Levings 1985). Little resembles small adults (e.g. Fig. 39.1, Wolff migration occurs between different adjacent 2014). substrates, and can result in genetically Juvenile: different races (Stanhope et al. 1992; Longevity: Stanhope et al. 1993). Growth Rate: Amphipod growth occurs in Salinity: Full salt water to brackish water conjunction with molting where the (range 5–25, Stanhope et al. 1993). exoskeleton is shed and replaced. Post-molt Temperature: individuals will have soft shells as the cuticle Tidal Level: Intertidal to 30 meter depths gradually hardens (Ruppert et al. 2004). (Bousfield 1979; Chapman 2007). Occurs in Food: Detritus, particularly from algal or drainage channels in South Slough of Coos vascular plant material. Research has shown Bay (+1.4 meters). that E. confervicolus will readily ingest Associates: Associates include the isopod, Zostera marina leaves (Harrison 1982), Gnorimosphaeroma insulare, (South Slough Enteromorpha linza and Pylaiella littoralis of Coos Bay) and the amphipod, Corophium (Pomeroy and Levings 1980) and individuals slamonis (Siuslaw Estuary). are capable of ingesting up to 0.21 mg Ulva Abundance: Often occurs in great numbers per individual per day (Price and Hylleberg and is the most common gammaroidean 1982). Ingestion of different algal substrates amphipod on the Pacific coast of North (e.g. Fucus distichus and Pelvetia fastigiata) America (Bousfield 1979). Up to 25,000 can manifest distinct pheromones between individuals per m2 comprising 5% of total substrate-specific, but geographically close, benthic fauna in June and 17% in August populations (Stanhope et al. 1992). (Sixes River, Martin 1980). Populations can

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12706 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Predators: Fish (e.g. juvenile salmonids, salmon. In: Federal Aid Progress Parsons 1985), birds and mallards (Batzer et Reports: Fisheries Research and al. 1993). Development Section. Behavior: 10. PARSONS, T. R., J. C. SHARP, and W. K. W. LI. 1985. The cultivation of Bibliography marine amphipods and their use as food for young salmonids. Zeitschrift 1. BARNARD, J. L. 1954. Marine fuer Angewandte Ichthyologie. 1:77- amphipoda of Oregon. Oregon State 84. Monographs, Studies in Zoology. No. 11. POMEROY, W. M., and C. D. 8:1-103. LEVINGS. 1980. Association and 2. BATZER, D. P., M. MCGEE, V. H. feeding relationships between RESH, and R. R. SMITH. 1993. Eogammarus confervicolus Characteristics of invertebrates (Amphipoda: Gammaridae) and consumed by mallards and prey benthic algae on Sturgeon and response to wetland flooding Robert's Banks, Fraser River Estuary. schedules. Wetlands. 13:41-49. Canadian Journal of Fisheries and 3. BATZER, D. P., and V. H. RESH. Aquatic Sciences. 37:1-10. 1992. Macroinvertebrates of California 12. PRICE, L. H., and J. HYLLEBERG. seasonal wetland and responses to 1982. Algal-faunal interaction in a mat experimental habitat manipulation. of Ulva fenestrata in False Bay, Wetlands. 12:1-7. Washington. Ophelia. 21:75-88. 4. BOUSFIELD, E. L. 1979. The 13. RAPPAPORT, R. 1960. The origin and amphipod superfamily Gammaroidea formation of blastoderm cells of in the northeastern Pacific region: gammarid crustacea. Journal of systematics and distributional ecology. Experimental Zoology. 144:43-59. Bulletin of the Biological Society of 14. RUPPERT, E.E., R.S. FOX, and R.D Washington. 3:297-357. BARNES. 2004. Invertebrate 5. —. 2001. The amphipod genus zoology: a functional evolutionary th Anisogammarus (Gammaroidea: approach, 7 Edition. Thomson Anisogammaridae) on the Pacific Brooks/Cole, Belmont, CA. coast of North America. 15. STANHOPE, M. J., M. M. Amphipacifica. 3:29-47. CONNELLY, and B. HARTWICK. 6. BOUSFIELD, E. L., and H. MORINO. 1992. Evolution of a crustacean 1992. The amphipod genus chemical communication channel: Ramellogammarus in fresh waters of behavioral and ecological genetic western North America: systematics evidence for a habitat modified, race and distributional ecology. Royal specific pheromone. Journal of British Columbia Museum. Chemical Ecology. 18:1871-1887. 7. CHAPMAN, J. W. 2007. Amphipoda: 16. STANHOPE, M. J., B. HARTWICK, Gammaridea, p. 545-611. In: The and D. BAILLIE. 1993. Molecular Light and Smith manual: intertidal phylogeographic evidence for multiple invertebrates from central California to shifts in habitat preference in the Oregon. J. T. Carlton (ed.). University diversification of an amphipod species. of California Press, Berkeley, CA. Molecular Ecology. 2:99-112. 8. HARRISON, P. G. 1982. Control of 17. STANHOPE, M. J., and C. D. microbial growth and of amphipod LEVINGS. 1985. Growth and grazing by water soluble compounds production of Eogammarus from leaves of Zostera marina. Marine confervicolus (Amphipoda: Biology. 67:225-230. Anisogammaridae) at a log storage 9. MARTIN, J. T. 1980. Oregon site and in areas on undisturbed Department of Fish and Wildlife habitat within the Squamish Estuary, studies of Oregon coastal chinook British Columbia. Canadian Journal of