Atlantic Ancula vs common freshwater nerite

Ancula gibbosa compared with Theodoxus fluviatilis

Taxonomic Classification

Rank	Atlantic Ancula	common freshwater nerite
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Mollusca (Mollusks)	Mollusca (Mollusks)
Class same	Gastropoda (Gastropoda)	Gastropoda (Gastropoda)
Order	Nudibranchia (Nudibranchia)	Cycloneritida (Cycloneritida)
Family	Goniodorididae	Neritidae
Genus	Ancula	Theodoxus
Species	Ancula gibbosa	Theodoxus fluviatilis

Evolutionary Relationship

Atlantic Ancula and common freshwater nerite share a common ancestor at the Class level: Gastropoda. (Gastropoda)

Conservation Status

Atlantic Ancula

LC — Least Concern

common freshwater nerite

LC — Least Concern

Physical Characteristics

Attribute	Atlantic Ancula	common freshwater nerite
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Atlantic Ancula

Habitat

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

Range

Distributed across Denmark, Norway, and Sweden.

common freshwater nerite

Habitat

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

Range

Found across Europe (11 countries).

Atlantic Ancula

The Atlantic Ancula (Ancula gibbosa) is a species in the genus Ancula. It is currently classified as Least Concern on the IUCN Red List. Typically found in terrestrial and aquatic habitats including forests and freshwater.

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.

Shared Countries

Both species can be found in 3 countries:

🇩🇰 Denmark 🇳🇴 Norway 🇸🇪 Sweden