Overview
The Ouachita rock pocketbook is a freshwater mussel inhabiting certain rivers and large creeks in or near the southern slope of the Ouachita Mountains. It has occurred in low densities from the time of its discovery, even within its preferred habitats, but has declined further in distribution and abundance in response to human modifications of its habitats, specifically construction and operation of large impoundments, channelization, water quality degradation from point sources and nonpoint sources of pollution, gravel excavation, and operation of land vehicles in streams. Additional potential threats include extreme conditions resulting from human-caused climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change and increased colonization of the Ouachita Rock Pocketbook's habitats by invasive aquatic species. The U. S. Fish and Wildlife Service has prepared a recovery plan for the Ouachita Rock Pocketbook and is working with other stakeholders to implement actions to conserve the species.
Scientific Name
Identification Numbers
Characteristics
Physical Characteristics
The outer shell layer of the Ouachita Rock Pocketbook is chestnut-brown to black with a silky luster and appears slightly iridescent when wet. The inner shell lining is usually salmon-colored in its upper reaches, white to light blue below, and has a dark prismatic border.
The shell of the Ouachita Rock Pocketbook reaches a maximum length of about 4.5 inches, is subovate (nearly egg-shaped) in outline, and moderately inflated. The posterior half of the shell typically exhibits low ridges that are crossed at times by smaller ridges. These and other distinctive details of the shell are used commonly to identify the species. The soft parts of the mussel have an anatomy typical for the subfamily to which the species belongs. Only the outer set of gills is used by the females as marsupia.
Food
Adults feed by filtering algae, other protists, microscopic animals, bacteria, and detritus from their surroundings. Larval mussels (glochidia) live on the body fluids of host fish they successfully parasitize. After metamorphosis, juveniles become free-living and use foot movements to collect bacteria, algae, and fine detritus until they become functional filter-feeders.
Life Cycle
As with most freshwater mussels, the life cycle of the Ouachita rock pocketbook includes sexual reproduction and a required parasitic stage. During spawning, males release sperm into the water column, some of which are taken into females of the species, which carry eggs in their gills. Fertilization results in larvae (known as glochidia) that are released from the females into the water column and must attach to a suitable fish host to continue development. Once metamorphosis is complete, juvenile mussels drop off the fish host and continue life in the stream bottom. Known fish hosts for this species include the golden shiner (Notemigonus crysoleucas), duskystripe shiner (Luxilus pilsbryi), and freshwater drum (Aplodinotus grunniens).
As with most freshwater mussels, the life cycle of the Ouachita rock pocketbook includes sexual reproduction and a required parasitic stage. During spawning, males release sperm into the water column, some of which are taken into females of the species, which carry eggs in their gills. Fertilization results in larvae (known as glochidia) that are released from the females into the water column and must attach to a suitable fish host to continue development. Once metamorphosis is complete, juvenile mussels drop off the fish host and continue life in the stream bottom. Known fish hosts for this species include the golden shiner (Notemigonus crysoleucas), duskystripe shiner (Luxilus pilsbryi), and freshwater drum (Aplodinotus grunniens).
Habitat
The Ouachita rock pocketbook lives in pools, backwaters, runs, and side channels of the streams where it occurs. The species inhabits stable stream bottoms containing gravel, sand, and other substrate materials. The Ouachita rock pocketbook always occurs within large, high-quality mussel beds containing a diversity of mussel species.
A natural body of running water.
Geography
The Ouachita rock pocketbook occurs in the Kiamichi River in southeastern Oklahoma, the Little River in southeastern Oklahoma and southwestern Arkansas, and the Ouachita River in central Arkansas. Shells of the species also have been recovered from Pine and Sanders creeks in northeast Texas.
Timeline
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