Description
Synonymy- This clam genus was described as Gnathodon Gray in Sowerby (in 1832) [non Goldfuss (in 1820)]; and as Rangia by Desmoulins 1832. The species was described as R. cuneata by Sowerby (in 1831), as Rangia cyrenoides by Conrad (in 1867), and Rangianella cuneata by Conrad (in 1868) (Abbott 1974; Conrad 1840; Conrad 1867)
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Mollusca | Bivalvia | Veneroida | Mactridae | Rangia |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1960 | Established | Expanding | Introduced | Regular Resident | Western Atlantic | Western Atlantic | Shipping(Ballast Water, Barge),Fisheries(Oysters-accidental) |
History of Spread
Conrad (1840) described Rangia cuneata (Gulf Wedge Clam) as 'an inhabitant of the estuaries of the Gulf of Mexico and occurring in the upper Tertiary formation in the bank of the Potomac River in Maryland and on the Neuse River, North Carolina '. Rangia cuneata is found in Pleistocene deposits ranging from NJ southward through the entire northern Gulf coast and northern South America (Hopkins and Andrews 1970). No living specimens were reported from the East Coast until about 1955 (Hopkins and Andrews 1970; Wells 1961). Prior to its discovery on the Atlantic Coast, R. cuneata was considered to range from the Gulf Coast of northern FL to TX (Fairbanks 1963). In the 1960s, it became abundant north to the Chesapeake Bay, and by 1988, it had colonized the Hudson River estuary (Carlton 1992).
A major question about this rapid range extension is whether it represents the result of anthropogenic introductions or represents the resurgence of small, previously unnoticed relict populations (Foltz et al. 1995; Hopkins and Andrews 1970), Pfitzenmeyer and Drobeck 1964), perhaps sparked by 'some unknown ecological change' (Hopkins and Andrews 1970). Given the relatively large size of this clam and the abundance of collectors on the Atlantic Coast, it seems much more likely that it was transported north by human vectors. Possible modes of introduction include transplanted seed oysters, oyster shipments, or ballast water (Carlton 1992; Pfitzenmeyer and Drobeck 1964). Gulf and Atlantic Coast populations appear to be genetically distinct at some loci, with an apparent boundary near Ocklochonee Bay (NE Gulf of Mexico) FL (Foltz et al. 1995). These data would appear to support the 'resurgence' model rather than an introduction from the Gulf of Mexico. However, the authors point out that the genetic data do not rule out other introduction scenarios, including introductions from the Gulf or Atlantic coasts of FL.
North American Records are summarized below:
Gulf of Mexico Estuaries - Conrad (1840) described this species as 'an inhabitant of the estuaries of the Gulf of Mexico.' It was reported from 'Northwest FL to TX' (Abbott 1954 cited by Pfitzenmeyer and Drobeck 1964), and from the Myakka and Peace Rivers FL in 1962 1962 (Pfitzenmeyer and Drobeck 1964).
Southeast US Atlantic Estuaries - Rangia cuneata is present on the FL coast at least as far south as the St. Lucie River FL (Foltz et al. 1995), but the history of the clam here has not been researched. The first reported Atlantic coast collections were from the Newport River NC in 1955-56 (Wells 1961). They were subsequently collected from the Altamaha River Delta, GA, 1958; and from Back Bay (the northern arm of Currituck Sound) in VA, in 1960 (Hopkins and Andrews 1970).
Chesapeake Bay records are summarized below:
Adjacent Southern Region- Living R. cuneata were found in 1960 by W. G. Hewatt in Back Bay, VA; near the NC border. (Hopkins and Andrews 1970).
James River- Rangia cuneata was first collected in 1963 (found by Jon Shidler); in 'an excellent oyster setting area from which seed oysters have been transplanted to other regions of the Chesapeake Bay and upper tributaries of the Potomac River'. 'Great quantities about three-quarters of an inch in length are being caught in the mesh of haul seine nets' (Pfitzenmeyer and Drobeck 1964).
York River- Rangia cuneata was established in the 1960s; Its range expanded downriver from river mile 20 to 10 and 15 after tropical storm 'Agnes' (Boesch et al. 1976).
Rappahannock River- Rangia cuneata was first collected in 1964 (Wass 1972), and was abundant by 1966-69 in the lower tidal-fresh oligohaline zone; between 30 and 40 mi. from the river mouth (Davies 1972).
Potomac River- Rangia cuneata was first collected in 1960-61. ' The point of introduction appears to have been in the upper Potomac area; probably Nanjemoy Creek or Port Tobacco River, if it was transported in with seed oysters. The State of Maryland has not planted seed oysters from the James River nor are there any private plantings in the Potomac river. The oldest specimens, probably four years of age, were found only in Nanjemoy Creek. ...The rate of dispersion during the first two years seems to have been slow but since 1963 the increase has been near phenomenal. Prior to the summer of 1963 they (R. cuneata) were unknown to the local watermen in this region but since then they have been becoming increasingly abundant. At the present time, great quantities about three-quarters of an inch in length are being caught in the mesh of haul seine nets.' (Pfitzenmeyer and Drobeck 1964, cited in Hopkins and Andrews 1970). By early 1970's this clam was found downriver as far as the Wicomico River ( Lippson 1973).
Upper Bay and Tributaries - Rangia cuneata was present in upper Bay by 1967, and abundant by 1968-1969 in the Northeast, Sassafras, Elk Rivers, and by 1969 in the Chesapeake and Delaware Canal; (Gallagher and Wells 1969). It is now abundant on the Susquehanna Flats in tidal fresh water (Posey et al. 1993) to the mouth of Patapsco, and northernmost edge of mouth of Chester River; confined to subestuaries further south (Lippson 1973). Depending on winter cold, and on ambient salinity, it is occasionally abundant in the Rhode River (Smithsonian Environmental Research Center, Edgewater MD) (Ruiz and Hines, unpublished data).
Delaware Bay - The first collection of R. cuneata was in 1971, at Oakwood Beach, NJ. It was considered abundant by 1974 between St. Jones River and Woodland Beach (Maurer et al. 1974). In 1979, R. cuneata was found at Delaware City, New Castle County, DE in the water system of the Getty Oil refinery, which it probably entered by way of the Chesapeake and Delaware Canal (Counts 1980).
Hudson River estuary- In 1988 R. cuneata was discovered in Haverstraw Bay NY. Possible modes of transport include ballast water, transport with oyster plantings, or ship's ballast water (Carlton 1992; Mills et al. 1997).
In 2005-2006, large numbers of small bivalves were discovered in the Scheldt estuary, Antwerp, Belgium, in bottom sediments and clogging the inlet pipes of a power-plant. These clams were identified as Rangia cuneata, probably transported as larvae in ballast water. This species now appears to be established in Belgium (Verween et al. 2006). In 2010, the Gulf Wedge Clam was discovered in the Vistula Lagoon, shared between Poland and the Kaliningrad Oblast of Russia . This population is increasing rapidly (Rudinskaya and Gusev 2010).
History References - Boesch et al. 1976; Carlton 1992; Conrad 1840; Counts 1980; Davies 1972; Foltz et al. 1995; Gallagher and Wells 1969; Hopkins and Andrews 1970; Lippson 1973; Maurer et al. 1974; Mills et al. 1997; Pfitzenmeyer and Drobeck 1964; Verween et al. 2006; Wass 1972; Wells 1961
Invasion Comments
Invasion Status - We consider a recent introduction of this species to Chesapeake Bay to be much more likely than a sudden resurgence of relict populations, given the rapidity of its spread in the Bay and northwards.
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | 1.0 | 34.7 | 18.0 | 32.0 |
| Salinity (‰) | 0.0 | 33.0 | 2.5 | 14.0 |
| Oxygen | well-oxygenated | |||
| pH | ||||
| Salinity Range | fresh-meso |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 17.0 | 17.0 |
| Typical Adult Size (mm) | 48.0 | 48.0 |
| Maximum Adult Size (mm) | 75.0 | 75.0 |
| Maximum Longevity (yrs) | 8.0 | 8.0 |
| Typical Longevity (yrs | 4.0 | 4.0 |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
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| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
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| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Rangia cuneata (Gulf Wedge Clam) is now abundant and widespread in oligohaline and mesohaline waters of Chesapeake Bay.
Fisheries - Rangia cuneata is important as a food resource for commercially important species [Callinectes sapidus (Blue Crab); Leiostomus xanthurus (Spot); Micropogonias undulatus (Atalntic Croaker); Pogonias cromis (Black Drum)] and for waterfowl (Cain 1972; Elbersole and Kennedy 1994). Rangia cuneata supports fisheries in the Gulf of Mexico and is occasionally eaten by people working in the Chesapeake oyster industry, but is not commercially utilized here. The main drawback to harvesting R. cuneata in many estuaries is that of pollution, often from domestic sewage (Cain 1972; Hines personal observation).
Industry - Rangia cuneata caused biofouling of pipes of the Getty oil refinery in Delaware City DE, clogging firehoses. This was the first report of industrial fouling associated with this species (Counts 1980).
Refs- Cain 1972; Counts, 1980; Elbersole and Kennedy 1994; Hines personal observation
Economic Impacts Outside of Chesapeake Bay
Rangia cuneata (Wedge Clam) is harvested in Gulf Coast states for food and the use of its shell in road building (Cain 1972).
References- Cain 1972
Ecological Impacts on Chesapeake Native Species
Rangia cuneata (Wedge Clam) is now abundant and widespread in oligohaline and mesohaline waters of Chesapeake Bay.
Food/Prey- Rangia cuneata has become a major prey item for many native aquatic predators including fishes, ducks, and Callinectes sapidus (Blue Crabs) (Cain 1972). The crabs preferred smaller clams, 1-2 cm long, because of increased handling time and energy expenditure on larger clams (Ebersole and Kennedy 1994).
Competition - Effects of R. cuneata on the native clams Mya arenaria (Softshell Clams) and Macoma balthica (Baltic Clams) are complex and subtle. Competition for food is likely; since suspension feeders can deplete plankton in the immediate vicinity. Macoma balthica, in the presence of R. cuneata switched to deposit feeding, resulting in increased rates of partial predation (siphons nipped) (Skilleter and Peterson 1994). This results in energetic costs of regeneration and could slow growth. These effects are apparently partly offset by structural refuges provided by R. cuneata (Skilleter 1994).
Habitat Change - Survivorship of the native bivalves Mya arenaris and Macoma balthica was increased in the presence of R. cuneata, but empty shells had similar effects (or greater in M. arenaria) than live clams, indicating that the shells of R. cuneata were providing a physical refuge (Skilleter 1994). The seagrass Ruppia maritima (Widgeon Grass), when present, apparently removed this protective effect, perhaps by interfering with burrowing, or by attracting predators (Skilleter 1994).
In in situ experiments, Rangia cuneata altered the composition and abundance of infaunal communities in the surrounding sediments in the Rhode River. Results are still being analyzed, and the effects appear to be complex. (R. Everett, personal communication).
The invasion of Rangia cuneata into oligohaline parts of the Bay has resulted in large biomasses of suspension feeding bivalves where previously they were scarce. This has probably affected phytoplankton distribution and planktonic and benthic foodwebs in these regions possibly in ways similar to those discussed by Phelps (1994) for Corbicula fluminea (Asian Freshwater Clam) in tidal fresh regions. In Chesapeake Bay, the large suspension-feeding biomasses of Rangia cuneata and C. fluminea have been considered as beneficial, as partially offsetting phytoplankton blooms stimulated by eutrophication, and partially compensating for the loss of the oyster biomass (Cerco et al. 2012). However, the effects of R. cuneata filtration, pseudofeces deposition, and other possible effects have not been well documented (R. Everett personal communication).
References - Cain 1972; Ebersole and Kennedy 1994; Phelps 1994; Skilleter 1994; Skilleter and Peterson 1994; R. Everett, personal communication, 1997.
Ecological Impacts on Other Chesapeake Non-Native Species
Rangia cuneata (Wedge Clam) is now abundant and widespread in oligo-and mesohaline waters of Chesapeake Bay.
Food/Prey - Rangia cuneata is eaten by Ictalurus furcatus (Blue Catfish), Lepomis microlophus (Redear Sunfish), and probably by I. punctatus (Channel Catfish), Cyprinus carpio (Common Carp) and other introduced benthivorous fishes (Cain 1972).
Competition - Competition is possible with Corbicula fluminea (Asian Freshwater Clam) in tidal fresh-oligohaline waters where their ranges overlap.
References- Cain 1972
References
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Carlton, James T. (1992) Introduced marine and estuarine mollusks of North America: An end-of-the-20th-century perspective., Journal of Shellfish Research 11: 489-505
Cerco, Carl F.; Noel, Mark R. (2010) Monitoring, modeling, and management impacts of bivalve filter feeders in the oligohaline and tidal fresh regions of the Chesapeake Bay system, Ecological Modelling 221: 1054-1064
Cooper, Rosalind B. (1981) Salinity tolerance of Rangia cuneata (Pelecypoda:Mactridae) in relation to its estuarine environment: A review, Walkerana 1: 19-31
Counts, Clement L., III (1980) Rangia cuneata in an industrial water system (Bivalvia:Mactridae), Nautilus 94: 1-2
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Rudinskaya, L. V.; Gusev, A. A. (2012) Invasion of the North American Wedge Clam Rangia cuneata (G.B. Sowerby I, 1831) (Bivalvia: Mactridae) in the Vistula Lagoon of the Baltic Sea, Russian Journal of Biological Invasions 3: 220-229
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