### Identification The Mayan Freshwater Crab (*Aceratophallus maya*) is a master of camouflage against the riverbed. It features a smooth, slightly convex carapace typically measuring 30–50mm in width. Its coloration is a study in earthy tones: ranging from a dull ochre to a deep, mahogany brown, often perfectly matching the saturated leaf litter of its home. Look closely at the claws (chelae); they are often unequal in size, with the larger "crusher" claw used for defense and heavy lifting. To distinguish it from the similar *Potamocarcinus* species, observe the frontal margin of the shell—*A. maya* lacks the aggressive serration found in its larger cousins, possessing a smoother, more refined edge.
### Habitat & Range This species is a specialist of the humid Neotropics, primarily found in the lush highlands of Chiapas, Mexico, and across the border into Guatemala. You won't find them in stagnant ponds; they crave the oxygen-rich, fast-flowing mountain streams and limestone-bottomed creeks of the rainforest. They are often found at elevations between 300 and 1,200 meters, tucked away in the "splash zone" where the air remains perpetually misty.
### Behaviour A secretive, nocturnal architect, *A. maya* spends its daylight hours wedged into limestone crevices or beneath water-logged timber. If you flip a rock in a Chiapas stream, you’ll see a sudden, frantic skittering—these crabs are surprisingly agile on land and in water. Unlike marine crabs, they exhibit "direct development." This means they skip the free-swimming larval stage entirely; females carry a small number of large, nutrient-rich eggs under their abdominal flap until they hatch into fully formed, microscopic "mini-me" crabs.
### Diet Functioning as the forest’s janitor, this crab is an opportunistic omnivore. It forages primarily on the "brown gold" of the stream: decomposing leaf litter and fallen tropical fruits. However, it isn't strictly a vegetarian; it will deftly hunt aquatic insects, snails, and even small fish if they venture too close to its crevice.
### Fascinating Fact Because they live in calcium-rich limestone environments, these crabs are "biological sponges." They actively sequester calcium from the water to build an exceptionally thick, stony exoskeleton, making them much harder and more "armored" than many other freshwater crustaceans!