Depth
Dardanus · Crustaceans (Crabs, Shrimps & Lobsters)

Greater Hermit Crab

Dardanus arrosor

0-40m
Depth Range
Variable
Max Size
Mediterranean
Distribution
0-40m
Depth Range
Variable
Max Size
Reef & Open
Habitat
Carnivore
Diet
Solitary
Social
LC
IUCN Status
Kingdom Animalia
Phylum Arthropoda
Class Malacostraca
Genus Dardanus
Species arrosor

Crustacean

Identification & Biology

  • IdentificationA large hermit crab with bright red to orange legs and claws, and a soft, coiled abdomen protected inside a borrowed gastropod shell. The left claw is noticeably larger than the right. The eyes are on stalks and the antennae are prominent.
  • SizeBody length up to 12 cm (excluding shell). Occupies large shells such as those of Tonna galea or Charonia tritonis.
  • Social HabitSolitary. Regularly changes shells as it grows. The shell is often colonised by anemones (Calliactis parasitica), which provide stinging defence in exchange for transport and food scraps.
  • HabitatSandy and muddy bottoms, rocky reefs, and seagrass meadows. Found wherever suitable large gastropod shells are available.
  • Depth1 to 100 m. Common between 5 and 40 m.
  • Feeds OnDetritus, carrion, algae, and small invertebrates. A generalist scavenger and omnivore.
  • DistributionEastern Atlantic and throughout the Mediterranean Sea. Common in Maltese waters.
  • DescriptionDardanus arrosor is the largest hermit crab commonly encountered by divers in Malta. The symbiotic relationship with the parasitic anemone Calliactis parasitica is one of the best examples of mutualism in Mediterranean marine life. The anemone's stinging tentacles deter octopuses and other predators, while the anemone benefits from food scraps and being transported to new feeding grounds.

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.

Greater Hermit Crab species card

Biology

Behaviour & Diet

Feeding Strategy

Opportunistic omnivore that scavenges carrion, detritus, and small invertebrates on sandy and rocky substrates. Uses its chelipeds to tear apart food items and pass fragments to the mouthparts.

Opportunistic scavenger

Reproduction

Females carry large clutches of eggs attached to modified pleopods inside the borrowed shell. Larvae hatch as planktonic zoeae and pass through several moult stages before settling.

Egg carrier

Behaviour & Defence

Withdraws entirely into its adopted gastropod shell and blocks the opening with its oversized right claw. It will aggressively fight conspecifics over desirable shells.

Shell retreat

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Where to Encounter in Malta

The following dive sites offer strong habitat match for Dardanus arrosor. 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.

View dive site ›
5-50m
Gozo

Blue Hole

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

View dive site ›
18-36m
South Malta

Um El Faroud

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

View dive site ›
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