''Ptychobranchus subtentum'', also known as the fluted kidneyshell, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

freshwater mussel Freshwater bivalves are molluscs of the order Bivalvia that inhabit freshwater ecosystems. They are one of the two main groups of freshwater molluscs, along with freshwater snails. The majority of bivalve molluscs are saltwater species that l ...

, an

aquatic Aquatic means relating to water; living in or near water or taking place in water; does not include groundwater, as "aquatic" implies an environment where plants and animals live. Aquatic(s) may also refer to: * Aquatic animal, either vertebrate ...

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the family

Unionidae The Unionidae are a Family (biology), family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is a ...

, the river mussels. This species is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the drainages of the

Cumberland River The Cumberland River is a major waterway of the Southern United States. The U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed June 8, 2011 river drains almost of southern Kentucky and ...

and the

Tennessee River The Tennessee River is a long river located in the Southern United States, southeastern United States in the Tennessee Valley. Flowing through the states of Tennessee, Alabama, Mississippi, and Kentucky, it begins at the confluence of Fren ...

in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

Reproduction

All Unionidae are known to use the gills, fins, or skin of a host fish for nutrients during the larval

glochidia The glochidium (plural glochidia) is a microscopic larval stage of some freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels. These larvae are t ...

stage. ''Ptychobranchus subtentum'' enclose their larvae in a membranous capsule that resembles the pupae of

black flies A black fly or blackfly (sometimes called a buffalo gnat, turkey gnat, or white socks) is any member of the family Simuliidae of the Culicomorpha infraorder. It is related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. Over 2,200 speci ...

. When a fish bites the capsule bait, the ''Ptychobranchus subtentum'' larvae are forced out through the mimic capsule's "eyes" and then attach to the gills of the host fish. Host species of this bradytictic mussel include '' Etheostoma obeyense'', '' Etheostoma rufilineatum'', '' Etheostoma flabellare'', ''

Etheostoma caeruleum The rainbow darter (''Etheostoma caeruleum'') is a small species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is native to No ...

'' and '' Cottus carolinae''.

References

subtentum Endemic molluscs of the United States ESA endangered species Taxa named by Thomas Say Bivalves described in 1825 Taxonomy articles created by Polbot {{Unionidae-stub