Depth
Astroides · Cnidarians (Jellyfish, Anemones & Corals)

Star Coral

Astroides calycularis

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 Cnidaria
Genus Astroides
Species calycularis

Cnidarian

Identification & Biology

  • IdentificationA colonial stony coral that forms bright orange to red encrustations on rock surfaces. Individual polyps are small, cup-shaped, and densely packed. When the polyps extend their tentacles, the colony looks like a field of tiny orange flowers.
  • SizeIndividual polyps up to 5 mm diameter. Colonies can cover areas of 30 cm or more.
  • Social HabitColonial. Forms dense encrustations on shaded rock surfaces. Polyps feed both day and night. One of the few ahermatypic (non-reef-building) colonial stony corals in the Mediterranean.
  • HabitatShaded rocky walls, cave entrances, and overhangs. Can tolerate some direct light but prefers shaded positions.
  • Depth0 to 50 m. Most common between 5 and 30 m.
  • Feeds OnPlankton and suspended organic particles captured by the polyp tentacles.
  • DistributionMediterranean Sea and adjacent eastern Atlantic (southern Spain, Canary Islands). Present in Maltese waters.
  • DescriptionAstroides calycularis is one of the most vivid and beautiful colonial corals in the Mediterranean. Its brilliant orange colour makes it a standout on any wall or cave entrance. It is a warm-water species that has been expanding its range northward in recent decades, likely in response to warming sea temperatures. It is listed in Annex II of the Barcelona Convention as a protected species.

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.

Star Coral species card

Biology

Behaviour & Diet

Feeding Strategy

Obtains most of its energy from symbiotic zooxanthellae algae in its tissues. Polyps also extend at night to capture zooplankton and suspended particles for supplementary nutrition.

Photosynthetic

Reproduction

A gonochoric brooder that incubates larvae internally. Planula larvae are released in summer and settle on hard substrate nearby, which leads to patchy, localised colony clusters.

Internal brooding

Behaviour & Defence

The calcium carbonate skeleton provides physical armour for the polyps. Retraction into the calice offers further protection, and the symbiotic algae help sustain the colony in nutrient-poor conditions.

Skeletal armour

Dive with diveshack

Where to Encounter in Malta

The following dive sites offer strong habitat match for Astroides calycularis. 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