Common Frillwort vs common sea hare

Fossombronia pusilla compared with Aplysia punctata

Key Differences

• Common Frillwort is Critically Endangered while common sea hare is Least Concern.

Taxonomic Classification

Rank	Common Frillwort	common sea hare
Kingdom	Plantae (Plants)	Animalia (Animals)
Phylum	Marchantiophyta (liverwort)	Mollusca (Mollusks)
Class	Jungermanniopsida (Jungermanniopsida)	Gastropoda (Gastropoda)
Order	Fossombroniales (Fossombroniales)	Aplysiida (Aplysiida)
Family	Fossombroniaceae	Aplysiidae
Genus	Fossombronia	Aplysia
Species	Fossombronia pusilla	Aplysia punctata

Conservation Status

Common Frillwort

CR — Critically Endangered

common sea hare

LC — Least Concern

Physical Characteristics

Attribute	Common Frillwort	common sea hare
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Frillwort

Habitat

Found across multiple habitat types including tropical and subtropical moist broadleaf forests, temperate broadleaf and mixed forests, and Mediterranean forests and woodlands spanning the Indomalayan and Palearctic realms. Populations are also found in montane and highland environments at higher elevations.

Range

Found across Asia (Taiwan) and Europe (5 countries). Currently classified as Critically Endangered on the IUCN Red List, this species faces significant conservation challenges across its range.

common sea hare

Habitat

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

Range

Distributed across Denmark, Norway, Portugal, and Sweden.

Common Frillwort

<em>Fossombronia pusilla</em>, commonly known as the common frillwort, is a small liverwort belonging to the family Fossombroniaceae within the division Marchantiophyta. This non-vascular bryophyte typically grows in moist, disturbed soils, clay banks, and damp pathways across its range in Europe and parts of Asia. The thallus is typically lobed and frilly in appearance, giving the species its common name. <em>Fossombronia pusilla</em> favors habitats with high moisture and reduced competition, often colonizing bare or sparsely vegetated ground following disturbance. Its geographic range spans temperate regions of western and central Europe into Asia, though populations have become increasingly fragmented. The species is currently assessed as Critically Endangered on the IUCN Red List, reflecting severe population declines likely driven by habitat loss, land drainage, and agricultural intensification. Biological traits such as lifespan, body size, and diet remain poorly documented for this species, as is common among many small bryophyte taxa. Like other liverworts, <em>Fossombronia pusilla</em> reproduces both sexually through spores and vegetatively. Conservation of this species depends on protecting moist, low-competition microhabitats and reducing disturbance to its specialized substrates.

common sea hare

<em>Aplysia punctata</em>, the common sea hare, is a large opisthobranch sea slug in the family Aplysiidae, order Aplysiida, found in the northeastern Atlantic Ocean and Mediterranean Sea, with confirmed records from Denmark, Norway, Portugal, and Sweden. This species typically inhabits shallow subtidal and intertidal zones with abundant macroalgae, feeding primarily on red and green algae — a diet that influences the color of the defensive purple ink it secretes when threatened. <em>Aplysia punctata</em> is a simultaneous hermaphrodite, capable of acting as both male and female during mating, and often forms mating chains involving multiple individuals. It can reach considerable size among European opisthobranch species, though body dimensions vary considerably with age and feeding conditions. The species is classified as Least Concern by the IUCN, reflecting stable populations across its coastal range. Biological traits for this species remain poorly documented in the scientific literature, including precise average data on lifespan, body length, weight, and detailed seasonal dietary patterns, though its general herbivorous feeding on macroalgae is well established.

Shared Countries

Both species can be found in 3 countries:

🇳🇴 Norway 🇵🇹 Portugal 🇸🇪 Sweden