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InvertebrateBrackishMarineIntermediate

Atlantic Marsh Fiddler Crab

Minuca pugnax

The Atlantic Marsh Fiddler Crab is a semi-terrestrial species that builds deep burrows. It requires a specialized paludarium with a sandy beach and brackish water, exhibiting fascinating social behavior.

Taxonomy

Class:Malacostraca

Order:Decapoda

Family:Ocypodidae

Subfamily:Ocypodinae

Genus:Minuca

Species:Minuca pugnax

Formerly known as:Uca pugnax

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Water Temperature

15 - 25 °C

pH Value

7.5 - 8.2

Water type

Brackish / Marine

Invertebrate type

Marine crab

Adult size

3 cm

Minimum group

>= 3

6 - 10 dKH

Ecological role

Scavenger

Species description

Geographical Origin and Habitat: Uca pugnax is native to the eastern coast of North America, ranging from Massachusetts to Florida. It inhabits salt marshes, tidal creeks, mudflats, and sandy shores, where it constructs deep burrows near the high tide mark.

Taxonomy: Belongs to the class Malacostraca, order Decapoda, family Ocypodidae, and genus Uca (often referenced under the subgenus Minuca). The common name 'fiddler crab' derives from the male's feeding motion, which resembles playing a violin.

Social Behavior: Highly social animals that live in dense colonies. Males defend their burrows vigorously using their oversized claw to threaten rivals and wave to attract females. They spend significant time on land foraging and maintaining their tunnels.

Coloration and Sexual Dimorphism: Carapace is typically dark brown, olive, or greyish, sometimes showing a blue tint. Sexual dimorphism is extreme: males possess one major cheliped that grows to a massive size and one minor claw, while females have two identical small claws.

Care, breeding and tankmates

Tank Setup: A specialized paludarium or aquaterrarium is mandatory. They cannot survive in a standard aquarium without dry land. Provide a sloped sandy beach area (at least 8-10 cm deep to allow burrowing) and a shallow brackish water zone.

Diet and Feeding: Detritivore and omnivore. They sift through wet sand and mud for algae, detritus, and organic micro-matter. Supplement their diet with sinking crustacean pellets, algae wafers, blanched vegetables, and occasional frozen foods.

Water Quality: Requires brackish water with a specific gravity of 1.005 to 1.015. Maintain temperatures between 15°C and 25°C, and pH between 7.5 and 8.2. Ensure the water section is well-aerated with a small sponge filter to keep water moving.

Compatibility and Tankmates: Best kept in a species-specific setup. Keep them in groups consisting of one male and multiple females to minimize male-on-male combat. Do not house with large fish or aggressive crabs that could eat them, especially when soft-shelled.

Aquarium Breeding: Breeding in home setups is highly unlikely. Although mating occurs and females carry eggs, the larvae are released into water as marine zoea, requiring specific open-ocean planktonic conditions and micro-foods to metamorphose.

Risks and Diseases: They are notorious escape artists; the enclosure must be completely sealed. Copper-based medications are highly toxic. Molting failure is a common cause of death, prevented by providing adequate calcium and iodine in the diet.

Geographic Origin and Distribution

Uca pugnax is native to the eastern coast of North America, ranging from Massachusetts to Florida. It inhabits salt marshes, tidal creeks, mudflats, and sandy shores, where it constructs deep burrows near the high tide mark.

Origin

Cosmopolitan or introducedNorth AmericaEast AsiaTropical oceans and reefs

Invertebrate profile

Diet: Detritivore
Ecological role: Scavenger
Shock sensitivity: Medium
Calcium and minerals: Medium
Molting: Yes
Reproduction: Oviparous
Compatibility & tankmates: Community

Image gallery

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Related species

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Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Mudflat Fiddler Crab

Minuca rapax

Species description

Care, breeding and tankmates