Brook Floater vs common freshwater nerite

Alasmidonta varicosa compared with Theodoxus fluviatilis

Key Differences

• Brook Floater is Vulnerable while common freshwater nerite is Least Concern.

Taxonomic Classification

Rank	Brook Floater	common freshwater nerite
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Mollusca (Mollusks)	Mollusca (Mollusks)
Class	Bivalvia (Bivalvia)	Gastropoda (Gastropoda)
Order	Unionida (Unionida)	Cycloneritida (Cycloneritida)
Family	Unionidae	Neritidae
Genus	Alasmidonta	Theodoxus
Species	Alasmidonta varicosa	Theodoxus fluviatilis

Evolutionary Relationship

Brook Floater and common freshwater nerite share a common ancestor at the Phylum level: Mollusca. (Mollusks)

Conservation Status

Brook Floater

VU — Vulnerable

common freshwater nerite

LC — Least Concern

Physical Characteristics

Attribute	Brook Floater	common freshwater nerite
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Brook Floater

Habitat

Native to North America, inhabiting ecosystems characteristic of the region.

Range

Found in United States. Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

common freshwater nerite

Habitat

Typically found in terrestrial and aquatic habitats including forests and freshwater.

Range

Found across Europe (11 countries).

Brook Floater

The Brook Floater (Alasmidonta varicosa) is a species in the genus Alasmidonta. It is currently classified as Vulnerable on the IUCN Red List. Native to North America, inhabiting ecosystems characteristic of the region.

common freshwater nerite

<em>Theodoxus fluviatilis</em>, commonly known as the common freshwater nerite, is a small aquatic gastropod mollusc belonging to the family Neritidae. This species is widely distributed across Europe, with documented occurrences in Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Hungary, Latvia, Norway, and Sweden. It typically inhabits freshwater environments, including rivers, streams, and lakes, where it grazes on algae and biofilm on hard substrates such as rocks and submerged wood. The common freshwater nerite is assessed as Least Concern on conservation metrics, reflecting its broad distribution and relatively stable populations across much of its European range. Biological traits of this species remain poorly documented in the scientific literature. <em>Theodoxus fluviatilis</em> plays an ecological role as a grazer in freshwater benthic communities, contributing to the regulation of algal growth on hard surfaces. The species typically favors clean, well-oxygenated waters and can serve as an indicator of water quality in freshwater systems. Its distinctive small, dome-shaped shell with variable patterning makes it recognizable among freshwater invertebrates.