Gecarcinidae

Distinguished from other crab families by the combination of terrestrial adult habits and branchiostegal lungs—inflated carapace regions over the gills with increased vascularization for air breathing. Most species exhibit pronounced claw asymmetry, with one cheliped substantially larger than the other. Distinguished from the related Sesarmidae (also terrestrial) by genetic and morphological characters; mitochondrial data place Gecarcinidae as sister to Sesarmidae. Distinguished from Coenobitidae (terrestrial hermit crabs) by lack of gastropod shell use and fully calcified abdomen.

Tropical terrestrial environments including coastal forests, mangroves, and inland areas near the coast. Adults occupy burrows in soil or leaf litter. Require proximity to marine environments for larval development. Some species show habitat partitioning by size class, with smaller individuals in areas of higher disturbance.

Tropical regions worldwide: Caribbean, Pacific coast of the Americas from Mexico to Colombia and offshore islands (including Gorgona Island, Revillagigedo Islands, Cocos Island, Galápagos), Central Pacific (Tokelau Islands), and Indo-Pacific (Taiwan). Johngarthia planata demonstrates a disjunct distribution spanning over 3,000 km in the East Pacific, with populations influenced by the California Current and Equatorial Countercurrent.

Activity patterns vary by species and locality. Reproductive activity typically coincides with rainy seasons: Cardisoma crassum shows gravid females July–September with maturation January–April; Cardisoma guanhumi reproductive peak May–June. Some species show diel activity patterns with nocturnal foraging.

Tropical omnivores; diet includes plant material, detritus, and opportunistic animal matter. Some species cause crop damage in agricultural areas.

Larval development occurs in marine environment; females release eggs into seawater where they hatch and develop through planktonic stages. Megalopae and early crab stages return to terrestrial habitats. Sexual maturity size varies by species: Cardisoma crassum males at 52.7–63.7 mm carapace width, females at 49.6–56.0 mm (morphometric estimates); Cardisoma guanhumi regulated at 64 mm minimum capture size in Puerto Rico.

Adults construct and occupy burrows. Males use enlarged chelipeds for combat and mating displays. Sexual dimorphism in claw size is pronounced, with males showing positive allometric growth in chelipeds while females show negative allometry. Adults undertake periodic migrations to the sea for breeding. Some species show ontogenetic color changes: Cardisoma guanhumi shifts from orange in small individuals through brown to blue in large adults.

Significant ecosystem engineers through burrowing activity, which influences soil structure, organic carbon distribution, and root systems in tropical forests. Important components of mangrove and coastal forest ecosystems. Contribute to nutrient cycling between terrestrial and marine environments through mass migrations and larval export.

Subject to artisanal fisheries throughout the tropics; Cardisoma guanhumi and Cardisoma crassum are harvested for food. Populations have declined due to overfishing, habitat degradation, and capture in protected areas. Management measures include closed seasons, minimum size limits, and protected area restrictions. Minimum landing sizes of 58–64 mm carapace width recommended or enforced in Panama and Puerto Rico. Color-based size estimation used by hunters to assess legal status. Some species considered agricultural pests due to crop damage.

• SesarmidaeAlso contains terrestrial crabs; distinguished phylogenetically as sister family, with Gecarcinidae representing a separate lineage within Grapsoidea. Morphological distinctions require detailed examination of gill chamber structure and genetic analysis.
• CoenobitidaeTerrestrial hermit crabs; distinguished by use of gastropod shells to protect the abdomen and soft, asymmetrical abdomens. Gecarcinidae have fully calcified, symmetrical abdomens and do not use shells.

• land crabs
• terrestrial crabs
• branchiostegal lungs
• tropical
• mangrove
• burrowing
• fisheries
• sexual dimorphism
• amphibious life cycle
• Grapsoidea

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Reproduction of Epigrapsus Notatus (Brachyura: Gecarcinidae) in Taiwan
• Size at sexual maturity in <i>Cardisoma crassum</i> (Brachyura: Gecarcinidae) from the Gulf of Montijo, Panama Talla de madurez sexual en <i>Cardisoma crassum</i> (Brachyura: Gecarcinidae) del Golfo de Montijo, Panamá Tamanho de maturidade sexual em <i>Cardisoma crassum</i> (Brachyura: Gecarcinidae) do Golfo de Montijo, Panamá
• Closing a distributional gap of over 3000 km and encountering an invisible barrier: new presence/absence data for Johngarthia planata Stimpson, 1860 (Decapoda, Brachyura, Gecarcinidae) for Central America and biogeographic notes on East Pacific Gecarcinidae
• Long-term monitoring of crab Cardisoma guanhumi (Decapoda: Gecarcinidae) captures in Jobos Bay Estuary, Puerto Rico
• PRIMER REGISTRO DE Gecarcinus (Johngarthia) planatus STIMPSON, 1860 (CRUSTACEA: GECARCINIDAE) PARA COLOMBIA Y NOTAS SOBRE SU ZOOGEOGRAFIA EN EL PACIFICO AMERICANO
• Dry season distribution of land crabs, Gecarcinus quadratus (Crustacea: Gecarcinidae), in Corcovado National Park, Costa Rica
• Influence of land crabs Gecarcinus quadratus (Gecarcinidae) on distributions of organic carbon and roots in a Costa Rican rain forest
• Densities, diel activity, burrow shape, and habitat characteristics of Gecarcinus (Johngarthia) planatus Stimpson, 1860 (Decapoda, Brachyura, Gecarcinidae) at Socorro Island, Revillagigedo, Mexico
• Systematics and ecology of the land crabs (Decapoda: Coenobitidae, Grapsidae and Gecarcinidae) of the Tokelau Islands, Central Pacific