Ucides cordatus

Distinguished from other mangrove crabs by combination of: large body size; strongly asymmetrical chelipeds with massive right crusher claw and slender left cutter claw; pronounced sexual dimorphism in carapace shape and coloration; strictly mangrove-associated habitat. Differs from congener Ucides occidentalis (Pacific coast) by Atlantic distribution. Separated from other Ocypodidae by terrestrial habits, deep burrowing behavior, and herbivorous diet focused on mangrove litter rather than deposit-feeding or carnivory.

Large crab with oval carapace. Males have flatter, more oval-shaped backs with distinct light blue central region and beige-white periphery. Females possess larger, more bulbous carapaces colored dull dark green with dark purple tones. Both sexes have legs of dark reddish-purple coloration. Left cheliped is sharp and slender, used for cutting and feeding; right cheliped is substantially larger and more robust, used for crushing. Females are larger than males on average (59.8±6.9 mm vs 69.8±6.7 mm carapace width in one studied population).

Strictly associated with mangrove forests, particularly Rhizophora mangle stands. Terrestrial habits with construction of deep burrows at tree bases, recorded to depths of 1.6 meters. Occupies both mangrove interior and edge habitats; juveniles and young crabs more abundant at anthropogenic edges, while adults and molting juveniles require interior forest conditions. Tidal mud flats and red mangrove roots used for mating and oviposition.

Western Atlantic Ocean from Florida (USA) south to Uruguay. Documented throughout Gulf of Mexico, Central America, Caribbean Antilles, northern South America, and Atlantic coast of Brazil. Specific populations studied in Piauí and other northeastern Brazilian states.

Mating season occurs November through January, with peak activity on three consecutive days monthly (second day most active). Nocturnal mating activity coincides with low tide periods. Reproductive behavior observed December 2007 and January-March 2009 in studied populations.

Primarily herbivorous, feeding on mangrove litter including leaves, bark, and roots. Shows preference for Rhizophora mangle over Avicennia germinans. Early life stages consume polychaete worms and microorganisms from sediments. Documented to ingest animal remains opportunistically. Deliberately ingests sediments collected outside burrows.

Sexual reproduction with separate sexes. Mating occurs during intermoult period when both sexes possess rigid carapaces. Females can mate before gonads fully mature, with ovulation occurring after some delay. Time from mating/sperm transfer to ovulation/oviposition varies. Egg-bearing females observed with ovaries in recovery phase; non-egg-bearing females may present mature ovaries. Males maintain spermatophores in posterior vas deferens when mature. Eggs transferred to female abdomen for external incubation.

Nocturnal mating migrations from burrows to ocean coast during reproductive season, creating phenomenon known as "a andada" (Portuguese: 'the walking'). Courtship involves male positioning before female, extending chelipeds and pereopods to form arch, drawing female closer, and introducing gonopod; duration 15-30 minutes. Male secretes foamy substance from oral cavity during courtship. Males polygynous, mating with multiple females per night. Male-male disputes involve claw prodding. Females may refuse males and withdraw. Males abandon females immediately after copulation. Egg transference onto abdomen most frequent observed behavior, primarily occurring while females perch on red mangrove roots (85% of egg-bearing females). Heavy rainfall triggers sudden activity increase during mating season.

Key ecosystem engineer in mangrove forests. Extensive burrowing and debris displacement loosens and aerates soil, increasing sedimentary surface area for oxidation processes. Burrows contribute to carbon dioxide balance in mangrove ecosystems, particularly during rainy season. Important in organic matter cycling and nutrient dynamics. Considered sentinel species for environmental quality, sensitive to heavy metals, fertilizer runoff, and xenobiotics.

Substantial economic importance for low-income coastal communities in Brazil as source of income and food. Subject to intensive artisanal harvesting with documented population declines since 1988. Legal restrictions on capture exist in some Brazilian states (e.g., Paraíba prohibits capture of females under 4.5 cm carapace width), though enforcement reported as inconsistent. Used as bioindicator for mangrove reserve effectiveness and environmental contamination. Population status informs conservation policy and habitat protection decisions.

• Ucides occidentalisCongeneric species distinguished by Pacific coast distribution (eastern Pacific from Mexico to Peru), allopatric with U. cordatus
• Cardisoma guanhumiAnother large terrestrial crab in overlapping range; distinguished by more uniformly blue or purplish coloration, different burrow architecture, and more generalized diet including greater animal matter consumption
• Goniopsis cruentataMangrove-associated graspid crab; smaller size, more aquatic habits, different claw symmetry pattern, and predatory/scavenging diet

• crustacean
• decapod
• brachyura
• mangrove
• terrestrial crab
• ecosystem engineer
• fisheries species
• bioindicator
• sexual dimorphism
• herbivore
• burrowing
• Atlantic distribution
• Brazil
• conservation concern

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• biodiversity | Blog - Part 44
• ESTADO DA ARTE DAS PESQUISAS COM O CARANGUEJO-UÇÁ, Ucides cordatus
• Reproductive behavior of the mangrove crab Ucides cordatus (Crustacea; Brachyura; Ucididae)
• Effect of salinity on modulation by ATP, protein kinases and FXYD2 peptide of gill (Na+, K+)-ATPase activity in the swamp ghost crab Ucides cordatus (Brachyura, Ocypodidae)
• Feeding ecology of the mangrove crab Ucides cordatus (Ocypodidae): food choice, food quality and assimilation efficiency
• EDGE EFFECTS ON THE ABUNDANCE OF THE CRAB Ucides cordatus (DECAPODA: OCYPODIDAE) IN A NEOTROPICAL MANGROVE