common grey sea slug vs Compact Stonewort

Aeolidia papillosa compared with Nitella mucronata

Key Differences

• common grey sea slug is Least Concern while Compact Stonewort is Vulnerable.

Taxonomic Classification

Rank	common grey sea slug	Compact Stonewort
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Mollusca (Mollusks)	Charophyta (Charophyta)
Class	Gastropoda (Gastropoda)	Charophyceae (Charophyceae)
Order	Nudibranchia (Nudibranchia)	Charales (Charales)
Family	Aeolidiidae	Characeae
Genus	Aeolidia	Nitella
Species	Aeolidia papillosa	Nitella mucronata

Conservation Status

common grey sea slug

LC — Least Concern

Compact Stonewort

VU — Vulnerable

Physical Characteristics

Attribute	common grey sea slug	Compact Stonewort
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

common grey sea slug

Habitat

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

Range

Distributed across Belgium, Chile, Denmark, Norway, and Sweden.

Compact Stonewort

Habitat

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

Range

Widely distributed across Europe (4 countries), North America (United States), and South America (Brazil). Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

common grey sea slug

<em>Aeolidia papillosa</em>, commonly known as the common grey sea slug, is a nudibranch mollusc belonging to the genus Aeolidia within the family Aeolidiidae. Despite the species name referencing terrestrial and aquatic habitats including forests and freshwater, <em>Aeolidia papillosa</em> is primarily a marine organism. Its range includes Belgium, Chile, Denmark, Norway, and Sweden, indicating a distribution across the North Atlantic and into South American waters. Common grey sea slug is assessed as Least Concern on the IUCN Red List. The species is typically found in intertidal and subtidal zones, where it preys on sea anemones and stores stinging cells from its prey in its dorsal cerata for defense. Biological traits of this species remain poorly documented in the scientific literature.

Compact Stonewort

<em>Nitella mucronata</em>, compact stonewort, is a freshwater macroalga in the family Characeae, belonging to the charophyte lineage considered the closest algal relatives of land plants. It has been recorded from fresh and brackish water bodies in Belgium, Brazil, Denmark, Norway, Sweden, and the United States, inhabiting clear, nutrient-poor lakes, ponds, and slow-moving streams. Stoneworts of the genus Nitella are delicate, translucent plants lacking the calcium carbonate encrustation typical of the related genus Chara, growing submerged in well-lit, oligotrophic aquatic environments. They typically form dense underwater meadows that provide important habitat for invertebrates and small fish, while also stabilising sediments and contributing to water clarity through nutrient uptake. <em>Nitella mucronata</em> is classified as Vulnerable by the IUCN, reflecting sensitivity to water quality deterioration, eutrophication from agricultural runoff and sewage, and the loss of clear, unpolluted water bodies across its range in Europe and beyond. The species is particularly vulnerable to increased phosphorus and nitrogen loading, which promotes algal blooms that shade out submerged macrophytes. Biological traits including average lifespan, reproduction rates, and morphological measurements remain poorly documented compared to more widespread charophyte species. Conservation of <em>Nitella mucronata</em> depends on improving water quality in its freshwater habitats and protecting oligotrophic water bodies from nutrient pollution.

Shared Countries

Both species can be found in 4 countries:

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