Encyclopaedia
Mudflat Fiddler Crab
Uca rapax
Small and active semi-terrestrial tropical crab (3 cm), native to the Western Atlantic, lives in colonies digging burrows in brackish mangrove mud.
- Family
- Ocypodidae
- Origin
- Atlantico occidentale tropicale, diffuso dalla Florida e dal Golfo del Messico fino al Brasile meridionale
- Origin
- Tropical oceans and reefsExtra-Amazon South AmericaCentral America and CaribbeanNorth America
- Tank use
- Used in 0 tanks
Share
18 °C - 28 °C
7.5 - 8.2
Brackish / Marine
Rimescolatore del substrato sabbioso
High
Species description
Geographical Origin and Habitat: Tropical Western Atlantic, distributed from Florida and the Gulf of Mexico to southern Brazil. Found in sheltered mangrove lagoons.
Taxonomy: Member of the family Ocypodidae, genus Uca (often classified as Leptuca). Features extreme sexual dimorphism.
Social Behavior: Semi-terrestrial. Digs deep burrows in wet mud or sand, spending much of its time on land interacting and waving.
Coloration and Sexual Dimorphism: Carapace displays grayish-green or yellowish tones. In males, the single giant signaling claw is light yellow or white.
Care, breeding and tankmates
Tank Setup: Requires a paludarium setup (land and water). Essential to provide a dry land area of moist sand for burrowing behaviors.
Diet and Feeding: Detritivore. Filters sand/mud for organic particles. Accepts crushed spirulina wafers, sinking herbivore pellets, and frozen foods.
Water Quality: Brackish water with salinity SG 1.005-1.015. Highly adaptable, preferring temperatures between 18 and 28 °C.
Compatibility and Tankmates: Peaceful. Unsuitable for deep aquariums. Best kept in small harems consisting of one male and multiple females.
Aquarium Breeding: Females carry egg masses under their tail, releasing planktonic larvae into saltwater during high tides. Spawning in tanks is rare.
Risks and Diseases: Drowning risk if kept in a water-only setup without land access. Excellent climbers; a tightly sealed lid is mandatory.
Invertebrate profile
- Type
- Fiddler crab
- Diet
- Detritivoro
- Ecological role
- Rimescolatore del substrato sabbioso
- Minimum group
- 3
- Adult size
- 3 cm
- GH
- n/a
- KH
- 6 dKH - 10 dKH
- TDS
- n/a
- Copper
- High
- Shock sensitivity
- Media
- Calcium and minerals
- Fornire calcio sufficiente tramite sabbia aragonitica per rinforzare il carapace.
- Molting
- Effettuano la muta all'interno delle loro gallerie nella sabbia umida. Non disturbare.
- Reproduction
- Rilascia larve zoea marine che non sopravvivono in acquaterrari domestici.
- Compatibility & tankmates
- Richiede un acquaterrario specifico. Non compatibile con acquari d'acqua profonda.
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Other recommended species with similar care requirements and water parameters.




