Bigeye thresher vs common freshwater nerite

Alopias pelagicus compared with Theodoxus fluviatilis

Key Differences

• Bigeye thresher is Endangered while common freshwater nerite is Least Concern.

Taxonomic Classification

Rank	Bigeye thresher	common freshwater nerite
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum	Chordata (Chordates)	Mollusca (Mollusks)
Class	Chondrichthyes (Cartilaginous Fish)	Gastropoda (Gastropoda)
Order	Lamniformes (Mackerel Sharks)	Cycloneritida (Cycloneritida)
Family	Alopiidae	Neritidae
Genus	Alopias	Theodoxus
Species	Alopias pelagicus	Theodoxus fluviatilis

Evolutionary Relationship

Bigeye thresher and common freshwater nerite share a common ancestor at the Kingdom level: Animalia. (Animals)

Conservation Status

Bigeye thresher

EN — Endangered

common freshwater nerite

LC — Least Concern

Physical Characteristics

Attribute	Bigeye thresher	common freshwater nerite
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Bigeye thresher

Habitat

Typically found in marine environments from coastal waters to deep ocean.

Range

Distributed across Colombia and Taiwan. Currently classified as Endangered 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).

Bigeye thresher

The Bigeye thresher (Alopias pelagicus) is a species in the genus Alopias. It is currently classified as Endangered on the IUCN Red List. Typically found in marine environments from coastal waters to deep ocean.

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.