The Guadalupe Fatmucket is a rare mussel that is exclusively found in the Guadalupe River Basin. The mussel was originally thought to be a variation of the Texas Fatmucket, which is found in the Colorado River Basin (Inoue 2018). In September 2021, the United States Fish and Wildlife Service (USFWS) proposed that the Guadalupe Orb be listed as endangered under the ESA and designated critical habitat in the Guadalupe and San Marcos rivers. This decision was based on a completed species status assessment for six central Texas mussels that identified declining populations as a result of reduced water quality and habitat destruction. The designated critical habitat identified for this species falls within the covered area of the Guadalupe River HCP.
Federal Endangered Species Act Status:
Candidate – Under Review
State of Texas Species Conservation Status:
Kerr and Kendall counties
The Guadalupe Fatmucket is a medium sized freshwater mussel with an elongated elliptical shape and offset hinge. The mussel is commonly yellow to green or tan in color and often has green or brown lines that run from the hinge line to the margin of the shell. This mussel has different shell shapes for the males and females, with the female having a more inflated shell (Howells 2014).
The Guadalupe Fatmucket can live for at least 13 years. (Howells 2010d). The male and female mussels begin spawning during late fall and early winter, between October and February. The mussels begin holding mature glochidia (larval stage of mussels) between February and July. (Seagroves and Schwalb 2017). The mussels are long-term brooders, and may not release mature glochidia until the summer of the following year. The adult mussels lure a sunfish or bass fish host in with her mantle and subsequently releases mature glochidia that attach to the gills of a variety of sunfish fish hosts (Johnson 2012). The attached glochidia will transform into juvenile mussels after about a month and fall onto the substrate of the waterbody where they will burrow for protection and continue development into adult mussels.
Habitat and Diet:
Guadalupe Fatmucket adults are filter feeders that siphon plankton, organic matter and small organisms out of the water and sediment. The juvenile glochidia receive nourishment from the gills of a fish host. The adults are found in bank and pool habitats of small sized rivers and streams in fine substrates of mud, silt, sand and gravel. They require water temperatures of less than 28°C (82°F), and salinities of less than 3 parts per thousand (USFWS SSA 2018).
Burlakova, L., Karatayev, A., Froufe, E., Bogan, A.E., and Lopes-Lima, M. (2018). A new freshwater bivalve species of the genus Cyclonaias from Texas (Unionidae: Ambleminae: Quadrulini) The Nautilus 132(2), 45-50.
Dudding, J., Hart, M., Morton, J., Robertson, C., Conway, K., Lopez, R., and Randklev, C. (2018). Host fish association for two highly imperiled mussel species from the southwestern United States: Fusconaia mitchelli (false spike) and Cyclonaias petrina (Texas Pimpleback). Thesis submitted to Texas A&M University. College Station, Texas.
Dudding, J. Hart, M., Khan, J.M., Robertson, C.R., Lopez, R., and Randklev, C.R. (2020). Reproductive life history of 2 imperiled and 1 widely distributed freshwater mussel species from the southwestern United States. Freshwater Science, 39(1).
Howells, R.G., Neck, R.W.. and Murray, H.D. (1996). Freshwater Mussels of Texas. Texas Parks and Wildlife Department Inland Fisheries Division. Austin, Texas.
Howells, R.G. (2010d). False spike (Quadrula mitchelli): Summary of Selected Biological and Ecological Data for Texas. BioStudies, 16
Howells, R.G. (2014). Field Guide to Texas Freshwater Mussels, 2nd edition. BioStudies, Kerrville, Texas. 141
Inoue, K., A.M. Pieri, and Randklev. C.R. (2018). Summary of preliminary genetic results of Lampsilis bracteata (Texas fatmucket), Truncilla cognata (Mexican fawnsfoot), Truncilla macrodon (Texas fawnsfoot), Potamilus amphichaenus (Texas heelsplitter), and Potamilus metnecktayi (Salina mucket) in Texas. Progress Report for U.S. Fish and Wildlife Service, Austin, TX.
Johnson, M.S., Caccavale. P.D., Randklev, C.R., Gibson, J.R., (2012). New and confirmed fish host for the threatened freshwater mussel Lampsilis bracteata (Gould, 1855), the Texas Fatmucket (Bivalvia: Unionidae). The Nautilus. 126(4), 148-149.
Randklev, C. R., Johnson, N.A., Miller, T., Morton, J.M., Dudding, J., Skow, J., Boseman, B., Hart, M., Tsakiris. E.T., Inoue, K. and Lopez. R. R. (2017c). Freshwater Mussels (Unionidae): Central and West Texas Final Report. Texas A&M Institute of Renewable Natural Resources, College Station, Texas.
Seagroves, L.A., and Schwalb, A.N., (2017). Reproductive ecology of Lampsilis bracteata (Bivalvia: Unionidae). Thesis submitted to Texas State University. San Marcos, Texas
United States Fish and Wildlife Service. (2018). Species Status Assessment Report for the Central Texas Mussels: False Spike (Fusconaia mitchelli), Texas Fatmucket (Lampsilis bracteata), Texas Fawnsfoot (Truncilla macrodon), Texas Pimpleback (Cyclonaias petrina), Guadalupe Fatmucket (Lampsilis sp. Cf. bractceata), and Guadalupe orb (Cyclonaias necki). Albuquerque, New Mexico.