Mangrove Crab Metopograpsus messor

Metopograpsus messor is a grapsid shore crab widely distributed across Indo-Pacific coastlines, including rocky intertidal zones, mangrove edges, and harbour walls from the Red Sea to the Pacific. It is a moderately large, agile, and fast-moving species with a squarish carapace in olive-grey to dark brown and strong flattened legs adapted for climbing vertical surfaces.

In captivity, M. messor requires a brackish paludarium with both a water section and a generous land area. Its natural habitat includes exposed rocky surfaces in the splash zone, so the setup should allow it to climb, hide in rock crevices, and access water freely. It is more robust than smaller mangrove sesarmids and requires a secure lid as it is an excellent climber.

This species is active and bold, foraging on algae, organic debris, small invertebrates, and plant material in both terrestrial and aquatic zones. Groups can be maintained in spacious setups but males may compete. It is sensitive to freshwater and will decline quickly without a brackish salt component. Breeding larvae require marine conditions.

Water: 20–28°C, pH 7.8–8.5, GH 12–25, KH 5–15; brackish 1.005–1.015 SG; rocky climbing structures. Tank: minimum 60 L paludarium; rocky intertidal zone, splash area, brackish water section; very secure lid — strong climber. Feeding: omnivore — algae, dried invertebrates, sinking pellets, blanched vegetables, fresh mussels; feed every 1–2 days. Breeding: larvae require full marine conditions; captive rearing through metamorphosis not practical. Compatibility: groups possible in large setups; males territorial; do not house with small invertebrates or slow fish.