''Potamonautes sidneyi'' is a species of

freshwater crab Around 1,300 species of freshwater crabs are 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 relea ...

in the family

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

. 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 (, also referred to as KZN and known as "the garden province") is a province of South Africa that was created in 1994 when the Zulu bantustan of KwaZulu ("Place of the Zulu" in Zulu) and Natal Province were merged. It is locate ...

, South Africa, from the foothills of the Drakensberg to the coast from

Port Shepstone Port Shepstone is a large town situated on the mouth of the Mzimkhulu River, the largest river on the KwaZulu-Natal South Coast of South Africa. It is located halfway between Hibberdene and Margate and is positioned 120 km south of Durban. ...

to Lake Sibayi. They are also found in the South African provinces of the

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 the Kgalagadi T ...

Mpumalanga Mpumalanga () is a province of South Africa. The name means "East", or literally "The Place Where the Sun Rises" in the Swazi, Xhosa, Ndebele and Zulu languages. Mpumalanga lies in eastern South Africa, bordering Eswatini and Mozambique. It ...

, North West, Gauteng, Free State,

Eastern Cape The Eastern Cape is one of the provinces of South Africa. Its capital is Bhisho, but its two largest cities are East London and Gqeberha. The second largest province in the country (at 168,966 km2) after Northern Cape, it was formed in ...

, and in the countries of

Eswatini Eswatini ( ; ss, eSwatini ), officially the Kingdom of Eswatini and formerly named Swaziland ( ; officially renamed in 2018), is a landlocked country in Southern Africa. It is bordered by Mozambique to its northeast and South Africa to its no ...

and Mozambique.

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 levels and are important

detritivore Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...

s; reducing the particle size of organic debris to present a source of nutrition to collector and filter-feeding river fauna, and ensure resource recycling within the river ecosystem. These crabs are a primary source of food for Cape clawless otters and

water mongoose The marsh mongoose (''Atilax paludinosus''), also known as the water mongoose or the vansire, is a medium-sized mongoose native to sub-Saharan Africa that inhabits foremost freshwater wetlands. It has been listed as Least Concern on the IUCN Red L ...

, and may also be eaten by

Nile monitor The Nile monitor (''Varanus niloticus'') is a large member of the monitor family (Varanidae) found throughout most of Sub-Saharan Africa and along the Nile, with invasive populations in North America. The population in West African forests and sa ...

References

{{Taxonbar, from=Q5411049 Potamoidea Crustaceans described in 1904 Taxa named by Mary J. Rathbun Freshwater crustaceans of Africa Arthropods of South Africa Arthropods of Eswatini Arthropods of Mozambique