common hydra vs common sea hare

Hydra vulgaris compared with Aplysia punctata

Key Differences

• common hydra is Not Evaluated while common sea hare is Least Concern.

Taxonomic Classification

Rank	common hydra	common sea hare
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum	Cnidaria (Cnidarians)	Mollusca (Mollusks)
Class	Hydrozoa (Hydrozoa)	Gastropoda (Gastropoda)
Order	Anthoathecata (Anthoathecata)	Aplysiida (Aplysiida)
Family	Hydridae	Aplysiidae
Genus	Hydra	Aplysia
Species	Hydra vulgaris	Aplysia punctata

Evolutionary Relationship

common hydra and common sea hare share a common ancestor at the Kingdom level: Animalia. (Animals)

Conservation Status

common hydra

NE — Not Evaluated

common sea hare

LC — Least Concern

Physical Characteristics

Attribute	common hydra	common sea hare
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

common hydra

Habitat

Native to Europe, inhabiting ecosystems characteristic of the region.

Range

Distributed across Denmark, Norway, and Sweden.

common sea hare

Habitat

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

Range

Distributed across Denmark, Norway, Portugal, and Sweden.

common hydra

<em>Hydra vulgaris</em>, commonly known as the common hydra, is a small freshwater cnidarian in the family Hydridae. Its conservation status has not been formally evaluated by the IUCN. The species is recorded from Denmark, Norway, and Sweden, with its native range understood to encompass Europe broadly. It typically inhabits slow-moving or still freshwater bodies such as ponds, lakes, and streams, where it attaches to aquatic vegetation or submerged substrates. The common hydra is notable for its remarkable regenerative capabilities and has been the subject of substantial biological research. Diet information for this species is not available in current records. Biological traits of this species remain poorly documented in the scientific literature.

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:

🇩🇰 Denmark 🇳🇴 Norway 🇸🇪 Sweden