Ucides

Members of Ucides can be distinguished from other mangrove crab genera by their robust, semi-terrestrial morphology adapted for burrowing in muddy substrates. The genus is placed in the monotypic subfamily Ucidinae within Ocypodidae. Species-level identification relies on geographic distribution: U. cordatus in the Atlantic and U. occidentalis in the Pacific. Males are larger than females; in U. cordatus, male carapace width averages 69.8 mm versus 59.8 mm in females.

Tidal mangrove forests and associated estuarine environments. Ucides cordatus occupies mud flats and red mangrove (Rhizophora mangle) roots, with males predominantly on mud flats (96.6%) and females preferentially on mangrove roots (77%). Habitat use is tidally influenced, with surface activity and burrowing behavior directly affected by tides and lunar cycles.

Ucides cordatus: Atlantic coast from Florida to Uruguay, including the Gulf of Mexico, Caribbean, and northern South America. Ucides occidentalis: Pacific coast from Mexico to Peru, including the Gulf of Guayaquil in Ecuador.

Reproductive activity in Ucides cordatus has been observed in December and January-March, with mating occurring on three consecutive days monthly. Heavy rainfall triggers sudden increases in surface activity.

Semi-terrestrial with complex life cycle involving extended burrowing behavior. Embryonic development occurs on the female abdomen; eggs are initially liquid in appearance when deposited on mangrove roots, becoming more solid elsewhere. Larval development has been achieved in laboratory conditions for U. occidentalis, though high mortality rates present challenges. All sampled individuals of U. cordatus in one study were sexually mature.

Nocturnal mating activity with males mating with multiple females each night. Courtship involves the male positioning in front of the female, extending chelipeds and second pereiopods laterally to form an arch, drawing the female close, raising his body, and inserting the gonopod. Copulation lasts 15-30 minutes, after which the male abandons the female immediately. Males secrete a foamy substance from the oral cavity during courtship and mating. Limited male-male disputes involve using claws to prod each other on the carapace or claws.

Key species in mangrove ecosystem nutrient cycling, particularly in organic matter decomposition. Contributes to soil loosening and aeration through extensive burrowing and debris displacement. Considered one of the most important biological components of mangrove ecosystems.

Important commercial fishery resource and source of income for low-income estuarine communities. Subject to national management and conservation action plans; reproductive closure periods (veda reproductiva) implemented in some regions. Declining stocks observed in Brazil due to intensive harvest pressure, habitat destruction, and disease.

• CardisomaBoth are semi-terrestrial mangrove crabs with burrowing habits, but Ucides is distinguished by subfamily Ucidinae placement and specific habitat partitioning between sexes (males on mud flats, females on mangrove roots) not reported in Cardisoma.
• Uca (fiddler crabs)Both occur in mangrove habitats, but Ucides lacks the extreme sexual dimorphism in claw size characteristic of Uca males, and Ucides shows more pronounced spatial segregation between sexes.

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Embryonic analysis and larval culture of Ucides occidentalis
• 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
• Larval cycle, ecology and distribution of the red mangrove crab (<i>Ucides occidentalis</i>) in the Gulf of Guayaquil, Ecuador: understanding multiple impacts on fishery sustainability