Large Mediterranean Hermit Crab

Geographical Origin and Habitat: Common in the Mediterranean Sea and adjacent waters of the eastern Atlantic (from Portugal to Cape Verde). Inhabits rocky shorelines, sandy substrates, and detrital beds down to 40 m.

Taxonomy: Member of the family Diogenidae. One of the largest hermit crabs in the Mediterranean, reaching 7-9 cm in length. Claws are robust with bumpy nodules. Legs covered in dense sensory hairs.

Social Behavior: Mutualistic symbiont. Lives in close association with the anemone Calliactis parasitica. It active transfers the anemones to its new shell by tapping on their base to induce detachment.

Coloration and Sexual Dimorphism: Bright red, scarlet, or intense reddish-orange color covering the entire body. Claws feature red and yellow tubercles. Eyes have short stalks and greyish cornea. No obvious sexual dimorphism.

Tank Setup: Requires a temperate Mediterranean tank equipped with a chiller. Provide a coarse sand or fine gravel substrate and heavy, secure rock structures to support climbing.

Diet and Feeding: Omnivorous scavenger. Highly voracious; feeds on frozen mysis, krill, fresh fish chunks, mussels, and clams. Readily accepts large sinking pellets.

Water Quality: Requires cool temperatures (15-22°C). Salinity SG 1.025-1.027, pH 8.1-8.4. Highly sensitive to copper treatments and elevated nitrates.

Compatibility and Tankmates: Not compatible with tropical setups. May prey on small bottom fish, snails, and starfish. Keep only with robust, cool-water Mediterranean fish.

Aquarium Breeding: Females carry eggs under their abdomen. Planktonic larval stages are highly complex and do not survive standard home aquarium filtration systems.

Risks and Diseases: Overheating (above 24°C) is lethal. High stress and mortality if suitable heavy replacement shells are unavailable during growth.