Aratus pisonii, Mangrove Manager

Photo of a mangrove tree crab by Olivia Salerno.

by Olivia Salerno

The mangrove tree crab, Aratus pisonii, is a specialized crab that lives in and manages mangrove ecosystems. Mangroves are special trees that live in the coastal intertidal zone and stabilize the sediment, prevent erosion, and absorb storm surge during large storms. Mangroves play a role as a nursery and habitat for much wildlife, including the mangrove tree crab, making it an important ecosystem in Florida.

Mangrove tree crabs have a quadrate body shape, with a mottled brown and olive color to help them blend in with their surroundings. They have large eyes that are set far apart from one another on each side of their carapace. They are a small species with males averaging about 2 cm long and females being slightly smaller. Mangrove tree crabs prefer to live in red mangroves, which are closest to the water. This is because these crabs are semi-terrestrial but need to keep their gills wet to breathe. They have adapted to living out of the water for quite a long time but replenish their gills with water every so often. They reach sexual maturity around 2 years old and live for about 3-4 years.

Photo by James St. John.

Mangrove tree crabs are an ecologically significant species in Tampa Bay and throughout western Atlantic regions. They are detritivores, so they consume dead organic material. Their diets consist of fallen mangrove leaves and crustacean corpses, including their own kin. They eat leaf litter and other organic materials around the mangrove roots, which contribute to the recycling of nutrients. They keep most of the energy within the mangrove forests by burying and consuming organic litter which is important for maintaining the health and functional maintenance of mangroves.