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You are viewing an archived site. The Chesapeake Bay Introduced Species Database project ended in 2020 and the database is no longer receiving updates. Learn more…
Image of Cyrenoida floridana

Cyrenoida floridana

Mollusks-Bivalves

Florida Marsh Clam

Florida Marsh Clams live in decaying marsh vegetation. This habitat, and their small size (19mm max), means that they are easily overlooked and uncommon in shell collections. They were first described in Florida in 1889 and there range was thought to extend from Brunswick, GA south to the Everglades, and northward to Charlotte Harbor, FL on the Gulf coast. In the 1950s and 1960s the clam was discovered in Chesapeake Bay, Delaware, and Beaufort NC. But due to their small size and habitat there was some uncertainty as to whether or not these northern populations were introduced. In 1982 a study was conducted that found that these northern populations were poorly adapted to the northern climate. Their reproductive cycle was out of sync and they have high winter mortality, suggesting that this clam was a recent immigrant. We believe these clams were transported in rafted marsh grass or mud on the decks of barges or coastal ships, or in mud on canal dredges coming through the Intracoastal Waterway.

Image Credit: shellsfromchina.com

Taxonomy Invasion History Ecology Impacts References

Description

Taxonomy

Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Cyrenoidacea Cyrenoididae Cyrenoida

Synonyms

Cyrenoidea floridana; Cyrenoides floridana; Cyrenella floridana

Invasion History

Chesapeake Bay Status

First Record Population Range Introduction Residency Source Region Native Region Vectors
1952 Established Stable Introduced Regular Resident Western Atlantic Western Atlantic Shipping(Dry Ballast,Barge)

History of Spread

Cyrenoida floridana (Florida Marsh Clam) was described from FL by Dall in 1889, and was believed to range from Brunswick GA south to the Everglades, and northward to Charlotte Harbor FL on the Gulf coast (Dall 1896). In 1952-53, J. P. E. Morrison collected it in Chesapeake Bay and DE (Morrison 1954). Abbott (1974) does not mention populations of this clam north of GA. The northern populations of C. floridana appeared to be disjunct. However, C. floridana was collected subsequently near Beaufort NC in 1966 (United States National Museum of Natural History Collections). Because of their small size, and their habitat among decaying marsh vegetation, 'it is easy to understand why they are so easily overlooked, and why they are so uncommon in shell collections' (Morrison 1954). P. Kat (1982), studying a DE population, concluded that maladaptive features of this species' reproductive cycle (starting an unsuccessful period of gamogenesis in the fall, as well as high winter mortality) suggested that this clam was a recent immigrant to the mid-Atlantic region. 'This relatively recent range expansion seems coincident with, and probably can be attributed to, the construction of the Intracoastal Waterway. This series of canals probably also provides avenues of dispersal for juveniles to peripheral areas subsequent to local extinctions caused by periods of severe climate.'

Chesapeake records are listed below:

Upper Bay - Cyrenoida floridana was collected in 1952-1954 in Grasonville MD (Eastern Bay), Deale MD (Herring Bay), and Dailsville MD (Little Choptank River) (Wass 1972).

Patuxent River - Cyrenoida floridana was collected in 1952-1954 in Sollers MD (Wass 1972).

Rappahannock River - Cyrenoida floridana was collected in 1952-1954 in Mollusk VA (Wass 1972).

Lower Bay - Cyrenoida floridana was collected in 1952-1954 in Greenvale Creek MD (Pocomoke Sound), Saxis VA (Pocomoke Sound); (Accomack County), and Bayford VA (Northampton County)/VA (1952-54) (Wass1972).

Delaware Bay- Cyrenoida floridana was collected in 1952-1954 in Bombay Hook National Wildlife Refuge DE and Cumberland County; NJ (1952-54) (Morrison 1954; P. Kat 1982), and in Canary Creek Marsh, Lewes DE (1975) (Leathem et al. 1976; P. Kat 1982).

Barnegat Bay- Angradi et al. (2001) collected Cyrenoida floridana in the estuary of the Mullica River, flowing into Barnegat Bay.

Recent Chesapeake collections of this clam have been scarce. However, Prezant et al. (2002) collected it on Assateague Island MD-VA, and Posey et al. (2003) reported it from two marsh areas (on Chester River and Prospect Bay, Queen Anne's County) on MD's Eastern Shore.

History References - Abbott 1974; Angradi et al. 2001; Dall 1896; P. Kat 1982; Leathem et al. 1976; Morrison 1954; Prezant et al. 2002; Wass 1972; United States National Museum of Natural History Collections

Invasion Comments

Probable Vector into Chesapeake Bay - P. Kat (1982) considered the Intracoastal Waterway to be the likeliest route of C. floridana's colonization of the mid-Atlantic region. However, he did not discuss its mode of transport along this waterway. C. floridana lacks planktonic larvae, so that active dispersal would involve adults or juveniles. Although the salinity tolerance of this clam is unknown, extensive colonization of the freshwater habitats along the canals seems unlikely. The lack of planktonic larvae and byssi make transport by fouling or ballast water unlikely. Possibly, C. floridana could be transported in rafted marsh grass or mud on the decks of barges or coastal ships, or in mud on canal dredges.

Alternate vector into Cheapeake Bay - Nineteenth century transport in dry ballast is also a possibility.

Ecology

Environmental Tolerances

For SurvivalFor Reproduction
Minimum Maximum Minimum Maximum
Temperature (ºC)
Salinity (‰)
Oxygen
pH
Salinity Range oligo-poly

Age and Growth

Male Female
Minimum Adult Size (mm) 13.0 13.0
Typical Adult Size (mm) 16.0 16.0
Maximum Adult Size (mm) 19.0 19.0
Maximum Longevity (yrs)
Typical Longevity (yrs

Reproduction

Start Peak End
Reproductive Season
Typical Number of Young
Per Reproductive Event
Sexuality Mode(s)
Mode(s) of Asexual
Reproduction
Fertilization Type(s)
More than One Reproduction
Event per Year
Reproductive Startegy
Egg/Seed Form

Impacts

Economic Impacts in Chesapeake Bay

Cyrenoida floridana (Florida Marsh Clam) has no economic impact in Chesapeake Bay, because of the small size and apparently low abundance of this clam .

Economic Impacts Outside of Chesapeake Bay

Cyrenoida floridana (Florida Marsh Clam) has no significant economic impact over its range, except possibly as a food item for waterfowl.

Ecological Impacts on Chesapeake Native Species

Present abundance of Cyrenoida floridana (Florida Marsh Clam) in Chesapeake Bay marshes is unknown. High densities of this clam recorded in DE marshes (P. Kat 1982; Leathem et al. 1976) suggest that it might have some local importance as a detritivore. However, the pulmonate snail Melampus bidentatus (Eastern Melampus) is probably much more important in this role because of its greater abundance.

References- P. Kat 1982; Leathem et al. 1976

Ecological Impacts on Other Chesapeake Non-Native Species

Cyrenoida floridana (Florida Marsh Clam) overlaps in habitat with the probably introduced species Myosotella myosotis and the cryptogenic Melampus floridanus (Florida Melampus) and Assiminea succinea (Atlatnic Assiminea), all gastropods. However, abundances of M. myosotis and A. succinea are usually low, making competition with these species unlikely.

References

Angradi, T.R.; Hagan, S. M.; Able, K. W. (2001) Vegetation type and the intertidal macroinvertebrate fauna of the brackish marsh: Phragmites vs. Spartina., Wetlands 21: 75-92

Dall, W. H. (1896) On the American species of Cyrenoidea, Nautilus 10: 51-52

Kat, Pieter W. (1982) Reproduction in a peripheral population of Cyrenoida floridana (Bivalvia: Cyrenoididae), Malacologia 23: 47-54

Leathem, Wayne; Kinner, Pete; Maurer, Don (1974) Northern range extension of the Florida marsh clam (Cyrenoida floridana) (Superfamily Cyrenoidacea), Nautilus 90: 93-95

Lippson, Alice Jane; Lippson, Robert L. (1984) Life in the Chesapeake Bay, , Baltimore. Pp.

Morrison, J.P.E. (1954) Some zoogeographic problems among brackish water mollusks, The American Malacological Union Annual Report 20: 7-10

Posey, Martin H.; Alphin, Troy D.; Meyer, David L.; Johnson, John M. (2003) Benthic communities of common reed Phragmites australis and marsh cordgrass Spartina alterniflora marshes in Chesapeake Bay., Marine Ecology Progress Series 261: 51-61

Prezant, Robert; Counts, Clement L.; Chapman, Eric J. (2002) Mollusca of Assateague Island, Maryland and Virginia: additions to the fauna, range extensions, and gigantism., Veliger 45: 337-355

Direct questions and comments to chesnemo@si.edu.

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