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Crustaceans of Zihuatanejo

SUBPHYLUM CRUSTACEA

-Animals (Kingdom Animalia)

-Arthropods (Phylum Arthropoda)

-Crustaceans (Subphylum Crustacea)

-Typical Crustaceans (Superclass Multicrustacea)

-Malacostracans (Class Malacostraca)

-Decapods, Isopods, and Allies (Subclass Eumalacostraca)

-Decapods and Krill (Superorder Eucarida)

-Decapods (Order Decapoda)

-Crabs, Lobsters, Shrimps, and Allies (Suborder Pleocyemata)

-True Crabs (Infraorder Brachyura)​

-Eubrachyuran Crabs (Zoosection Eubrachyura)

-Thoracotrematan Crabs (Zoosubsection Thoracotremata)

-Land, Shore, and Marsh Crabs (Superfamily Grapsoidea)

-​Land Crabs (Family Gecarcinidae)

-Sesarmid Marsh Crabs (Family Sesarmidae)

-Square-back American-Marsh Crabs (Genus Armases)


These crabs are usually found in intertidal zones and can be found up to 50 m inland; they can thrive in a variety of habitats as well. Individuals are common among rubble and litter above the intertidal zone. While these crabs are often deemed to be detritivores, they are highly omnivorous and will supplement a detritus diet with microscopic insects and invertebrates.

Square-back Marsh Crabs

Armases (Genus)

Diet

  • Omnivorous, feeding on decaying leaves, mangrove litter, algae, fungi, seeds, insects, worms, snails, carrion, and other small crustaceans.

  • Also scavenges dead animals and opportunistically preys on small invertebrates.

  • Plays an important ecological role in breaking down leaf litter and recycling nutrients in coastal wetlands.

Range

  • Found throughout tropical and subtropical coastal regions of the Americas.

  • Along the Pacific coast, species of Armases occur from the Gulf of California south through Sinaloa, Nayarit, Jalisco, Colima, Michoacán, Guerrero (including the Zihuatanejo region)

  • The most likely species in the Zihuatanejo region include Armases occidentale and Armases gorei.

Habitat

  • Inhabit mangrove forests, estuaries, salt marshes, tidal creeks, mudflats, and coastal wetlands.

  • Often found beneath driftwood, rocks, fallen logs, and leaf litter, or climbing mangrove roots and low vegetation.

  • Many species are semi-terrestrial and can move considerable distances inland while remaining closely associated with humid coastal environments.

Size

  • Carapace width: 15–30 mm (0.6–1.2 in), depending on species.

  • Weight: Typically 5–20 g.

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