Parasesarma pictum is a mudflat crab

Crab

True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

, belonging to the Sesarmidae

Sesarmidae

Sesarmidae is a family of crabs, previously included in the Grapsidae by many authors. Several species, namely in Geosesarma, Metopaulias and Sesarma, are true terrestrial crabs. They do not need to return to the sea even for breeding.-Genera:...

 family (subfamily Sesarminae), which is endemic to East Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

. This crab typically inhabits mangrove

Mangrove

Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...

 swamps, preferring the upper intertidal region

Intertidal zone

The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...

 of estuaries

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

, and living in small crevices and abandoned holes made by other species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

. It eats leaf litter and other vegetation. The breeding season of P. pictum is between May and September.

Like other sesarmid crabs, P. pictum has a square carapace

Carapace

A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

. Its chela

Chela

Chela has two main meanings. One derivation comes from Hindi from Sanskrit , meaning "slave" or "servant". In English, the word means a religious student or disciple...

e are is covered with scaly tubercle

Tubercle

A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....

s that wear down as the crab ages, and some short seta

Seta

Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....

e (hairs). The inside of the claw of the crab is smooth, although many ridges and fine granule

Granule

Granule is a generic term used for a small particle or grain. The generic term is employed in a variety of specific contexts.* Granule , visible structures in the photosphere of the Sun arising from activity in the Sun's convective zone...

s are present on the movable portion; these ridges and granules are smaller in female and juvenile

Juvenile (organism)

A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...

 crabs than in adult males. The top portion (merus) of the walking legs of this crab are broad relative to the lower limb.