Liimina

Liimina is a small genus of freshwater mussels (Bivalvia) belonging to the family Ellipticidae. First described in 1907 by the American malacologist Edith Hodgson, the genus was erected to accommodate a distinct group of species previously assigned to the genus Lima. The type species, Liimina transversa, was collected from the upper tributaries of the Mississippi River. Subsequent phylogenetic studies based on mitochondrial DNA have supported the monophyly of Liimina, distinguishing it from closely related genera by a unique hinge ligament structure and shell microstructure.

The genus contains three recognized species: Liimina transversa, Liimina robusta, and Liimina marginata. These mussels are characterized by robust shells ranging from 35 to 70 millimeters in length, a slightly compressed profile, and an interior nacreous layer of pale pink. Their gill and digestive tract anatomy have been documented in detail in the monograph by J. K. Thompson (1953).

Liimina species are distributed across the central United States, inhabiting rivers and large streams with moderate flow and silty substrates. They are filter feeders, filtering suspended particulate matter and contributing to nutrient cycling within aquatic ecosystems. Population assessments indicate that Liimina transversa has a stable status, whereas Liimina robusta is listed as Near Threatened due to habitat degradation and water quality issues.

Conservation efforts for Liimina species focus on water quality improvement, riparian zone restoration, and monitoring of population dynamics. The genus remains a subject of taxonomic interest due to its distinct morphological characteristics and the ecological role it plays in freshwater habitats.