Common Hermit Crab
Pagurus bernhardus
A coldwater marine hermit crab native to the North Atlantic. It is an active and voracious scavenger that requires a specialized chiller-equipped aquarium and is not suitable for tropical setups.
Temperatura da água
8 - 18 °C
Valor de pH
7.9 - 8.4
Tipo de água
Marinho
Tipo invertebrado
Hermit crab
Tamanho adulto
8 cm
Grupo mínimo
>= 1
KH
8 - 12 dKH
Papel ecológico
Scavenger
Sensibilidade ao cobre
High
Descrição da espécie
Geographical Origin and Habitat: Widely distributed in the North Atlantic Ocean, North Sea, Baltic Sea, and down to the western Mediterranean. Found in rocky tide pools and seafloors down to 100 m. They are commonly found in tide pools, sandy shores, and deep offshore benthic zones. They are well-adapted to cold-water environments.
Taxonomy: Member of the family Paguridae. Distinguished by its right claw, which is significantly larger and more robust than the left. Grows to approximately 8 cm in total length. They are the type species of the genus Pagurus, representing typical marine hermit crabs. Their taxonomic history is well-documented.
Social Behavior: Highly active and curious. Constantly scavenges the substrate for organic matter. Juveniles occupy shallow intertidal zones, while larger adults migrate to deeper waters. They show a strong preference for Buccinum undatum shells as they grow larger. Shell fights can occur if resources are limited.
Coloration and Sexual Dimorphism: Body color ranges from light orange to reddish-brown. Claws feature pale, granular bumps. Oval dark eyes on short stalks. No visible external sexual dimorphism. Their soft abdomen is coiled to fit securely inside spiral snail shells. The walking legs are hairy and help grip rocky surfaces.
Cuidado, criação e companheiros de tanque
Tank Setup: Must be kept in a coldwater or temperate marine setup with a chiller. Provide a sandy or fine gravel substrate and empty gastropod shells (e.g. Littorina for young, Buccinum for adults). A chiller may be necessary if the room temperature rises above 20°C (68°F) in summer. Ensure good water circulation throughout the tank.
Diet and Feeding: Omnivorous scavenger and detritivore. Accepts frozen foods (mysis, brine shrimp, chopped seafood), pieces of mussels, small fish, and sinking pellets. Provide a mix of algae-based foods and meaty foods like chopped krill or shrimp. Supplement with commercial hermit crab pellets.
Water Quality: Essential to keep water cool (8-18°C). Tropical temperatures are lethal. Salinity SG 1.024-1.026, pH 7.9-8.4. Sensitive to copper treatments and elevated nitrates. Ensure high oxygenation by using an air stone or a powerful return pump. Keep ammonia and nitrite levels strictly at zero.
Compatibility and Tankmates: Not reef-safe. Suitable only for coldwater marine tanks. May prey on live snails if empty shells are lacking. Peaceful with larger, cool-water fish. Keep them with temperate species, avoiding tropical fish that require higher temperatures. They are compatible with cold-water anemones.
Aquarium Breeding: Females incubate eggs under their abdomen. Microscopic larval stages are pelagic and complex, and do not survive standard home aquarium filtration systems. Egg development is temperature-dependent, taking longer in colder winter waters. Females carry the eggs on their pleopods for weeks.
Risks and Diseases: Overheating (above 20°C) causes rapid death. High stress and mortality if suitable replacement shells are unavailable during growth. Watch for signs of shell rot on their exoskeleton, which can indicate poor water quality. Ensure iodine is present to support molting.
Origem e distribuição geográfica
Widely distributed in the North Atlantic Ocean, North Sea, Baltic Sea, and down to the western Mediterranean. Found in rocky tide pools and seafloors down to 100 m. They are commonly found in tide pools, sandy shores, and deep offshore benthic zones. They are well-adapted to cold-water environments.
Origem
Oceanos tropicais e recifesEuropa, Mediterrâneo e Ásia Ocidental
Perfil de invertebrados
- Dieta
- Omnivore
- *Pagurus bernhardus* is an opportunistic bottom feeder that relies on scavenging to survive. In an aquarium, they happily accept sinking meaty pellets, chunks of clam or shrimp, and various macroalgae. Feeding them a diverse diet ensures they receive the necessary nutrients for robust health.
- Papel ecológico
- Scavenger
- Serving as a key detritivore in temperate shorelines, *Pagurus bernhardus* recycles organic debris and dead organisms. This continuous cleaning action prevents the buildup of toxic ammonia and hydrogen sulfide in the wild. In an aquarium, they perform the exact same beneficial sanitation duties.
- Tamanho adulto
- 8 cm
- Risco de salto
- Yes
- Due to the heavy nature of their adopted shells, *Pagurus bernhardus* is incapable of jumping. They are adept at climbing textured background walls and thick algae stands, but escape is highly unlikely. Standard rimmed aquariums generally provide sufficient containment without heavy latching lids.
- Sensibilidade ao choque
- Medium
- *Pagurus bernhardus* is particularly vulnerable to heat shock if placed in standard tropical aquarium temperatures. Maintaining water consistently between 50-65°F (10-18°C) is absolutely critical. They also require slow acclimation to any salinity changes to prevent osmotic shock.
- Cálcio e minerais
- Medium
- Regular dosing or high-quality water changes are necessary to provide the calcium and alkalinity *Pagurus bernhardus* needs. Cold-water systems can sometimes suffer from depleted trace elements if not monitored properly. Calcium is critical for their successive molts and general vitality.
- Muda
- Shell growth
- During their molting phase, *Pagurus bernhardus* will seek a quiet, dark crevice to cast off its old exoskeleton. This process is highly stressful, and they must not be handled or disturbed during this time. Make sure several empty, appropriately sized shells are scattered around the tank for them.
- Reprodução
- Oviparous
- Reproduction in the home aquarium is an incredibly rare event for *Pagurus bernhardus*. They release planktonic larvae that require a cold, nutrient-rich water column to survive and metamorphose. Replicating the specific tidal and seasonal cues needed to trigger successful spawning is virtually impossible for most hobbyists.
- Compatibilidade e companheiros de tanque
- Community
- *Pagurus bernhardus* can be somewhat aggressive toward smaller slow-moving invertebrates if food or shells are scarce. They are best kept in a cold-water biotope with hardy anemones, robust starfish, and temperate fish species. Snails may occasionally become victims if the crab decides it wants a new home.
Modelos e parâmetros científicos
SeaLifeBase
Acesso aos dados científicos oficiais da espécie
SeaLifeBase v26.04Dados sincronizados em: 15/06/2026
- Resiliência
- Baixa (4,5 - 14 anos)
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