Depth
Pachygrapsus · Crustaceans (Crabs, Shrimps & Lobsters)

Marbled Crab

Pachygrapsus marmoratus

0-36m
Depth Range
Variable
Max Size
Mediterranean
Distribution
0-36m
Depth Range
Variable
Max Size
Rocky Reef
Habitat
Photosynthetic
Diet
Solitary
Social
LC
IUCN Status
Kingdom Animalia
Phylum Arthropoda
Class Malacostraca
Genus Pachygrapsus
Species marmoratus

Crustacean

Identification & Biology

  • IdentificationA small, flat-bodied crab with a square-shaped carapace covered in a distinctive dark marbled pattern of green, brown, and cream. The legs are banded and well adapted for gripping wet rock surfaces. Very fast-moving.
  • SizeCarapace width up to 4 cm. A small but abundant species.
  • Social HabitFound in large numbers on wave-splashed rocks. Extremely agile, running sideways at speed and jumping between rocks to escape threats. Active during the day.
  • HabitatIntertidal zone and splash zone on rocky shores. One of the most characteristic animals of Mediterranean rocky coastlines.
  • DepthIntertidal to 1 m. Rarely submerged, preferring the splash zone above the waterline.
  • Feeds OnAlgae scraped from rock surfaces, detritus, and small invertebrates. Primarily a grazer.
  • DistributionEastern Atlantic from Brittany to West Africa, and throughout the Mediterranean and Black Seas. Abundant on all Maltese rocky shores.
  • DescriptionPachygrapsus marmoratus is probably the most commonly seen crustacean in Malta, visible on virtually every rocky shoreline from the splash zone to the waterline. Its remarkable speed and agility make it difficult to catch by hand. Snorkellers and shore divers will see them scattering across the rocks at the water's edge. They play an important role in controlling algal growth on coastal rocks.

Range

Habitat & Distribution

Found across the Mediterranean, inhabiting rocky reef environments. Active from the surface down to 36m 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

Rocky Reef habitats, typically at depths of 0-36m. 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.

Marbled Crab species card

Biology

Behaviour & Diet

Feeding Strategy

Herbivorous grazer that scrapes algae and biofilm from intertidal rocks. Also scavenges on organic debris and occasionally small invertebrates in the splash zone.

Algal grazer

Reproduction

Females carry egg masses beneath the abdomen and release larvae into the water. Breeding occurs through the warmer months, with multiple broods per season.

Seasonal spawning

Behaviour & Defence

Exceptionally agile on rocks, capable of rapid sideways sprinting and leaping between surfaces to evade predators. Its dark marbled pattern provides effective camouflage on wet rock.

Rapid escape

Dive with diveshack

Where to Encounter in Malta

The following dive sites offer strong habitat match for Pachygrapsus marmoratus. 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