Potamonautes sidneyi is a species of freshwater crab

Freshwater crab

There are around 1,300 species of freshwater crabs, distributed throughout the tropics and subtropics, divided among eight families. They show direct development and maternal care of a small number of offspring, in contrast to marine crabs which release thousands of planktonic larvae. This limits...

 in the Potamonautidae

Potamonautidae

Potamonautidae is a family of freshwater crabs endemic to tropical parts of Africa and adjacent islands, including Madagascar, the Seychelles, Zanzibar, Mafia, Pemba, Bioko, São Tomé, Príncipe and Sherbro Island. It comprises 18 extant genera and 138 extant species...

 family. The common name is the Natal river crab or Sidney's river crab, although they may also be referred to as "river crabs", "fresh water crabs" or "land crabs".

Distribution

This species is widespread in KwaZulu-Natal

KwaZulu-Natal

KwaZulu-Natal is a province of South Africa. Prior to 1994, the territory now known as KwaZulu-Natal was made up of the province of Natal and the homeland of KwaZulu....

, South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, from the foothills of the Drakensberg

Drakensberg

The Drakensberg is the highest mountain range in Southern Africa, rising to in height. In Zulu, it is referred to as uKhahlamba , and in Sesotho as Maluti...

 to the coast from Port Shepstone to Lake Sibayi. They are also found in the South African provinces of the Northern Cape

Northern Cape

The Northern Cape is the largest and most sparsely populated province of South Africa. It was created in 1994 when the Cape Province was split up. Its capital is Kimberley. It includes the Kalahari Gemsbok National Park, part of an international park shared with Botswana...

, Mpumalanga

Mpumalanga

Mpumalanga , is a province of South Africa. The name means east or literally "the place where the sun rises" in Swazi, Xhosa, Ndebele and Zulu. Mpumalanga lies in eastern South Africa, north of KwaZulu-Natal and bordering Swaziland and Mozambique. It constitutes 6.5% of South Africa's land area...

, North West

North West (South African province)

North West is a province of South Africa. Its capital is Mafikeng. The province is located to the west of the major population centre of Gauteng.-History:...

, Gauteng

Gauteng

Gauteng is one of the nine provinces of South Africa. It was formed from part of the old Transvaal Province after South Africa's first all-race elections on 27 April 1994...

, Free State

Free State

The Free State is a province of South Africa. Its capital is Bloemfontein, which is also South Africa's judicial capital. Its historical origins lie in the Orange Free State Boer republic and later Orange Free State Province. The current borders of the province date from 1994 when the Bantustans...

, Eastern Cape

Eastern Cape

The Eastern Cape is a province of South Africa. Its capital is Bhisho, but its two largest cities are Port Elizabeth and East London. It was formed in 1994 out of the "independent" Xhosa homelands of Transkei and Ciskei, together with the eastern portion of the Cape Province...

, and in the countries of Swaziland

Swaziland

Swaziland, officially the Kingdom of Swaziland , and sometimes called Ngwane or Swatini, is a landlocked country in Southern Africa, bordered to the north, south and west by South Africa, and to the east by Mozambique...

 and Mozambique

Mozambique

Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

.

Behaviour

These crabs commonly shelter in burrows that they dig into the side of muddy river banks or under rocks in rivers. They come out from their shelters at night or after rain. They mate outside of water and the female carries the eggs and young under her broad tail until they are fully formed miniature crabs. She then releases them into quiet pools in streams where the juveniles spend much of their time in the water. The young shelter under leaves, stones and among tree roots that enter the water. They spend more time on land as they mature.

Ecological significance

River crabs utilise energy from diverse trophic level

Trophic level

The trophic level of an organism is the position it occupies in a food chain. The word trophic derives from the Greek τροφή referring to food or feeding. A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism...

s and are important detritivore

Detritivore

Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...

s; reducing the particle size of organic debris to present a source of nutrition to collector and filter-feeding

Filter feeder

Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...

 river fauna, and ensure resource recycling within the river ecosystem

Ecosystem

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

. These crabs are a primary source of food for Cape clawless otters

African Clawless Otter

The African clawless otter , also known as the cape clawless otter or groot otter, is the second largest freshwater species of otter. African clawless otters are found near permanent bodies of water in savannah and lowland forest areas...

 and water mongoose

Marsh Mongoose

The Marsh Mongoose, or Water Mongoose, is a medium-sized mammal but a large mongoose. Weight can range from , with an average range of . From the head to the base of the tail, these animals range from , with the tail adding . It is a member of the mongoose family and the only member of its genus...

, and may also be eaten by Nile monitor

Nile monitor

The Nile Monitor, Water Leguaan, or River Leguaan is a large member of the monitor lizard family ....

s.