A mangrove tree crab. Image from wikimedia commons and used under the creative commons license.  Taken by Ianaré Sévi


The Aratus pisonii is in the Eukaryote domain.  A characteristic that places the tree crab into the Eukaryote domain would be its membrane bound organelles.  This includes organelles within the boundary of the cell membrane including the nucleus and mitochondria.  Eukarya covers a very wide range of organisms including plants, animals and fungi as well as a variety of protozoa including Pyrocystis fusiformis

Major Clade
The major clade Opisthkonta plays host to the Aratus pisonii.  The major characteristic represented by the tree crab that places it into this clade is its rear-mounted flagellum.  Fungi, such as Morchella esculentoides, are another member of this clade.

The tree crab falls into the Kingdom Animalia.  Characteristics that make this true include the lack of a cell wall and the absence of chloroplasts.  The tree crab is also heterotrophic, as it does not fix its own carbon.

Arthropoda is the phylum to which the tree crab belongs too.  Major characteristics for this include the presence of an exoskeleton, jointed legs and appendages, bilateral symmetry, and a body divided into distinct parts.  Another member of this phylum is Xylocopa virginica, or the eastern carpenter bee.  The tree crab also falls into the subphyla of the Crustaceans.  Synapomorphies of this group include two body regions, five or more pairs of legs, two pairs of antennae, and the ability to reside in both aquatic and terrestrial habitats (Arizona, 1997).

Phylagenetic tree for the animal phyla.

This phylogenetic tree is representing the phyla within the Kingdom Animalia.  The mangrove tree crab is in Kingdom Animalia and falls into the Arthropod  phylum.

The mangrove tree crab falls into the Malacostraca class.  In being in this class, the crab exhibits three main sections including the abdomen, thorax, and the head.  It also has about 19-20 jointed body systems.  Another characteristic of this class is the presence of an open circulatory system (New Hampshire Public Television, 2014).

The order of the tree crab is Decapoda.  Classification here includes the presence of ten legs, as well as a well-developed carapace (Decapod Crustaceans, 1999). 

The tree crab belongs to the family Sesarmidae.  The distinguishing characteristic for this would be the ability of the crab to climb trees in the terrestrial environment (Cumberlidge et al, 2009).

Aratus pisonii is currently the only species in the genus Aratus.  It characteristic here is the lack of lateral spines on its carapace (Smithsonian, 2009).

Phylogeny of Sesarmidae Genera.

Illustrated is a phylogenetic relationship displaying the genera of the family Sesarmidae. (Shubert et al, 2006)

Once again, the tree crab is the only species within its genus, so its distinguishing characteristic separating it from other members of its family is the lack of lateral spines on its carapace (Smithsonian, 2009).

 Go back to the Home page or learn more about this species in the Form and Function page.