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Lampsilis straminea (Conrad, 1834)
Rough Fatmucket
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G5
State Rank: S2
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): No
2025 SGCN Priority Tier:
Element Occurrences (EOs) in Georgia: 45
Habitat Summary for element in Georgia: Small creeks to rivers in slow to moderate current; sand, sandy mud and gravel substrates
Strongly inflated, oval or truncate shell to 119 mm. Sexually dimorphic. Anterior margin rounded, posterior margin rounded, truncate and wide in females. Posterior ridge rounded, posterior slope forming a very minimal wing. Periostracum light orange to rusty brown without obvious rays. Teeth triangular and heavy. Nacre white (Williams et al., 2008; Williams et al., 2014).
Adult L. straminea are distinct from other species in Georgia. Lampsilis floridensis and Lampsilis teres most closely resemble L. straminea; however, L. straminea is generally less elongate and more inflated as well as trending more towards brown or orange coloration as opposed to the yellow color most often seen in L. floridensis and L teres.
L. straminea is found in stable, sandy substrates in large and medium sized rivers. This species tends to prefer habitat away from the center of rivers in moderate flow. Some individuals have been found in lacustrine habitats (Williams et al., 2014) but it is generally uncommon.
The diets of unionids are poorly understood but are believed to consist of algae and/or bacteria. Some studies suggest that diets may change throughout the life of a unionid with juveniles collecting organic materials from the substrate through pedal feeding and then developing the ability to filter feed during adulthood (Vaughn and Hakenkamp, 2001).
Like all unionids, L. straminea has an obligate parasitic life cycle. Larval mussels, known as glochidia, develop in water tube present in the gills of the female mussel and are released when disturbed by an appropriate host fish. L. straminea is believed to be a long-term brooder, like other members of its genus, and is presumed to be gravid from spring to late summer. Glochidia attach to the gills, fins, and skin of the host fish and encyst as an ectoparasite. Typical glochidia infestation appears to be minimally invasive to the host fish and is not fatal. Glochidia remain attached to the host for several weeks to several months before dropping off as juvenile mussels. These juveniles hopefully land in a new, suitable location and burrow into the sand where they feed on detritus using their foot and eventually grow into filter-feeding, adult mussels. This species is a host generalist and specific host fishes for L. straminea have been identified in the family Centrarchidae (bass and sunfishes), Cyprinidae (carps and minnows), Ictaluridae (catfishes and madtoms), and Poeciliiadae (mosquitofish). Many of these hosts have been identified through laboratory inoculations, and the hosts which naturally interact with L. straminea in the wild likely differ. L. straminea has a large, elaborate mantle lure and therefore is likely to target larger fish species which feed on fish and large invertebrates. Further research is needed to identify important host fish species.
Surveyors should consider sampling during periods when female individuals are spawning or brooding as this species may have higher detection rates during this period. However, since basic life history information for many of Georgia’s unionids is lacking, sampling during periods when closely related species are spawning or brooding may increase probability of detection. Investigators should conduct tactile searches of stabilized sand and fine gravel substrates (i.e. sand around an embedded boulder or bedrock) away from the immediate margins of the river in high to moderate flows. The low number of individuals of this species that have been collected make specific survey recommendations difficult.
This species is distributed along gulf coast tributaries from the Escambia River in Florida and Alabama to the Suwannee River in Georgia and Florida. In Georgia, L. straminea is most common in the Ochlockonee and Apalachicola River basins.
Like most native freshwater mussels in Georgia, L. straminea is threatened by habitat destruction in the form of flow alteration, excessive water withdrawal, watershed land use changes, impoundments, and pollution. While the host fish requirements for L. straminea are not well understood, freshwater mussels are dependent on them to complete their life cycle, and threats to host fish or barriers to host fish movement are also serious threats.
Conservation of L. straminea will primarily rely on habitat protection in the Apalachicola and Ochlockonee River basins in the form of drainage area, riparian, and water resource management. Further research into the specific distribution, life history, host fish, and habitat requirements of this species are still needed to guide management efforts. L. straminea is most abundant in the larger portions of the rivers where it is found in Georgia and reducing disturbances in these areas will be beneficial to this species.
Vaughn C.C. and C.C. Hakenkamp. 2001. The functional role of burrowing bivalves in freshwater ecosystems. Freshwater Biology 46:1431-1446.
Williams, J.D., R.S. Butler, G.L. Warren, and N.A. Johnson. 2014. Freshwater Mussels of Florida. University of Alabama Press, Tuscaloosa, Alabama.
Matthew Rowe
1/9/2020