Atlantic Gray Seal vs common freshwater nerite

Halichoerus grypus compared with Theodoxus fluviatilis

Key Differences

• Atlantic Gray Seal is Vulnerable while common freshwater nerite is Least Concern.

Taxonomic Classification

Rank	Atlantic Gray Seal	common freshwater nerite
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum	Chordata (Chordates)	Mollusca (Mollusks)
Class	Mammalia (Mammals)	Gastropoda (Gastropoda)
Order	Pinnipedia (Seals & Sea Lions)	Cycloneritida (Cycloneritida)
Family	Phocidae (True Seals)	Neritidae
Genus	Halichoerus	Theodoxus
Species	Halichoerus grypus	Theodoxus fluviatilis

Evolutionary Relationship

Atlantic Gray Seal and common freshwater nerite share a common ancestor at the Kingdom level: Animalia. (Animals)

Conservation Status

Atlantic Gray Seal

VU — Vulnerable

common freshwater nerite

LC — Least Concern

Physical Characteristics

Attribute	Atlantic Gray Seal	common freshwater nerite
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Atlantic Gray Seal

Habitat

Typically found in diverse terrestrial and aquatic ecosystems.

Range

Distributed across Belgium, Denmark, Norway, Portugal, and Sweden. 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).

Atlantic Gray Seal

The Atlantic Gray Seal (Halichoerus grypus) is a species in the genus Halichoerus. It is currently classified as Vulnerable on the IUCN Red List. Typically found in diverse terrestrial and aquatic ecosystems.

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 4 countries:

🇧🇪 Belgium 🇩🇰 Denmark 🇳🇴 Norway 🇸🇪 Sweden