Depth
Marthasterias · Echinoderms (Starfish, Urchins & Brittle Stars)

Spiny Starfish

Marthasterias glacialis

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 Echinodermata
Genus Marthasterias
Species glacialis

Echinoderm

Identification & Biology

  • IdentificationThe largest starfish in the Mediterranean. Five long, robust arms covered in rows of prominent white-tipped spines. Colour is variable: green, brown, olive, or grey with patches of lighter and darker tones. Small blue spots may be visible at the base of some spines.
  • SizeArm span up to 70 cm. By far the largest starfish species in the Mediterranean.
  • Social HabitSolitary. An active predator that can move relatively quickly for a starfish. Sometimes found in pairs during breeding. Can regenerate lost arms.
  • HabitatRocky reefs, boulder fields, seagrass meadows, and mixed substrates. Found on a wide range of habitats.
  • Depth0 to 180 m. Common between 5 and 50 m.
  • Feeds OnMussels, oysters, sea urchins, barnacles, and other invertebrates. Prises open bivalve shells using sustained arm pull, then inserts its everted stomach to digest the prey inside its own shell.
  • DistributionEastern Atlantic from Norway to West Africa, and throughout the Mediterranean Sea. Common in Maltese waters.
  • DescriptionMarthasterias glacialis is the top invertebrate predator on many Mediterranean rocky reefs. It hunts mussels and sea urchins with relentless patience, using the hydraulic power of thousands of tube feet to prise open shells. A single large specimen can consume several mussels per week, making it an important force shaping the community structure of rocky reefs. The largest individuals in Malta are impressive animals.

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.

Spiny Starfish species card

Biology

Behaviour & Diet

Behaviour & Defence

Protected by sharp spines that deter predators. Handle with care -- spines can cause injury even after death.

Defensive

Dive with diveshack

Where to Encounter in Malta

The following dive sites offer strong habitat match for Marthasterias glacialis. 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.

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