Aplysia · Molluscs (Octopus, Nudibranchs & Shellfish)

Depilatory Sea Hare

Aplysia depilans

0-40m

Depth Range

Variable

Max Size

Mediterranean

Distribution

Mollusc

Identification & Biology

IdentificationA large, soft-bodied sea slug with a broad, rounded body and two prominent ear-like rhinophores on the head. Dark brown to olive-green, sometimes with pale blotches. When disturbed, releases a cloud of deep purple ink as a defence mechanism.
SizeBody length up to 30 cm. Weight up to 400 g. One of the largest opisthobranch molluscs in the Mediterranean.
Social HabitMostly solitary but can form mating chains of several individuals during breeding season, with each animal acting as both male and female simultaneously.
HabitatRocky reefs, seagrass meadows, and areas with abundant algal growth. Moves slowly across the substrate grazing on algae.
Depth0 to 20 m. Primarily a shallow-water species.
Feeds OnBrown and red algae. A specialised herbivore that accumulates algal pigments in its skin.
DistributionEastern Atlantic and throughout the Mediterranean Sea. Seasonally common in Maltese shallow waters.
DescriptionAplysia depilans is one of the largest sea slugs in the Mediterranean and is named for the historical belief that touching it would cause hair loss (depilatory), which is not true. When disturbed, it releases a dramatic cloud of purple ink derived from the red algae it eats. This ink is thought to confuse predators by masking scent trails. Often seen by snorkellers in shallow, weedy areas.

Range

Habitat & Distribution

Found across the Mediterranean, inhabiting reef & open environments. Active from the surface down to 40m depth.

Where Malta divers have spotted this species

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Sightings are logged by divers using our What Did You See? dive-log tool. View the full live sightings map.

Detail

Preferred Environment

Reef & Open habitats, typically at depths of 0-40m. Most commonly encountered by divers at the shallower end of its range.

Encounter Tips

Best approached slowly and calmly. Avoid casting shadows directly over the animal. Neutral buoyancy and patience increase encounter success significantly.

Biology

Behaviour & Diet

Feeding Strategy

Grazes on red and green algae in shallow rocky habitats, ingesting pigments that give its body a characteristic brownish or purplish colour.

Herbivore

Reproduction

A simultaneous hermaphrodite that mates in chains of multiple individuals. It lays tangled strings of pink or orange eggs on algae and rock surfaces.

Hermaphrodite

Behaviour & Defence

Releases a copious purple ink from its ink gland and a separate white secretion called opaline, both of which deter predators by irritating their chemosensory organs.

Purple ink

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Where to Encounter in Malta

The following dive sites offer strong habitat match for Aplysia depilans. All are accessible on a guided dive with diveshack.

5-30m

North Malta

Cirkewwa

Rocky reef with caves, arches and ledges hosting a rich diversity of reef species.

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5-50m

Gozo

Blue Hole

One of the Med's most famous reef dive sites. Rocky walls and archways covered in life.

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18-36m

South Malta

Um El Faroud

The wreck lies on a sandy bottom surrounded by rocky reef -- a diverse habitat attracting reef species.

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IUCN Red List Least Concern

Conservation Status

This species is assessed as Least Concern on the IUCN Red List. Mediterranean populations face ongoing pressure from fishing activity, habitat degradation, and climate-driven changes to prey availability.

Source: iNaturalist Guide #888
by Lesley Clements (CC BY-SA)
diveshack Mediterranean Marine Life guide