Rare crab reappears in the wild

More than a century later, a rare crab species has been rediscovered in Ebo Forest. With the discovery of a crab thought to be extinct, this iconic African forest has once again cemented its importance as a biodiversity hotspot.

Stretching over 2,000 square kilometres of lush greenery, mountains and river valleys, Cameroon’s Ebo Forest is a haven for nature and science. While surrounding areas in southwestern Cameroon continue to face threats from logging and other destructive projects, the forest (while still intact) also plays a key role in providing shelter to its rich and diverse inhabitants – including the world’s only community of chimpanzees that use tools to crack nuts and catch termites.

Among the animals and plants most threatened by human activities in the region are various species of freshwater crabs that live mainly in the rivers and streams of the Ebo Forest. There are 22 species of crabs in southwestern Cameroon, nine of which are endemic. Louisea yabassi is one of them. It is a small, semi-terrestrial crab with a light brown and rust color, very rare and lost to humankind since the first specimens were discovered and collected in 1908.

"That's what makes it so unique," said Dr. Pierre A. Mvogo Ndongo, a cancer scientist and lecturer at the University of Douala in Cameroon. He and his colleagues at Northern Michigan University in the United States and the Humboldt Museum of Natural History in Berlin realized that the 1908 L. yabassi specimens were misidentified and were likely a completely different species. Unfortunately, it was no longer possible to extract DNA from them to reveal their evolutionary history.

Discovered for the first time in more than 110 years

The specimens collected in the Ebo Forest undoubtedly belong to the genus Louisea, but it is not yet certain whether they belong to any known species. In 2019 and 2020, Pierre and his team ventured into the tropical oasis of Ebo for two separate field surveys in search of L. yabassi in the hope of confirming the continued presence of the species, as well as collecting and identifying other types of freshwater crustaceans.

Both expeditions were very successful: in 2019, they found 20 individuals in and near two streams flowing into the Dibamba River in coastal Cameroon, and in 2020, another 15 were found in one of the streams.

"It's amazing - we rediscovered a specimen of Louisea yabassi and became the first scientists to see this species in more than 110 years," said Pierre, who also rediscovered the Sierra Leone crab, one of the most sought-after rare species in the wild. "To be honest, we thought L. yabassi was probably extinct." With the two populations, the team can finally compare the new individual's physical features with the original, and compare the DNA with that of other crabs of the same genus, verifying the identity of L. yabassi. However, the discovery also revealed that the species was already in danger.

About the Future

In the areas they surveyed, much of the natural vegetation has been destroyed by logging, agriculture, and pesticides. These activities will disturb and destroy L. yabassi's habitat, directly affecting their survival. Given how small the rediscovered population is, "I began to worry about the long-term survival of this species," Mvogo Ndongo said.

Louisea yabassi (female). (Photo courtesy of Pierre A. Mvogo Ndongo)

L. yabassi is an important member of the freshwater community of Ebo Forest. Ecologically, it is part of a complex food web that includes Nigeria-Cameroon Chimpanzee, the Western Gorilla, Goliath Frog, Forest Elephant, Preuss's Red Colobus Monkey, Drill and African Grey Parrot. Rare crabs are found in these rivers and streams, which also serve as spawning grounds for other invertebrates and fish, and provide safe havens for many of the forest's other charismatic aquatic animals, such as crocodiles, pythons and swamp otters.

These crabs sometimes venture onto land and sometimes eat plants and animals on the forest floor, similar to other species of African freshwater crabs. According to the scientists, a carefully designed conservation plan is needed to save the species from extinction. "A more complete understanding of the biology of this species and the threats it faces can be used to educate and help local people adopt practices that are less destructive to forest ecosystems and the crabs' most sensitive habitats," Pierre explained.

His next project will examine population levels, ecology, habitat requirements and dangers of several threatened freshwater crabs in Cameroon, including L. yabassi. Crucially, the rediscovery of L. yabassi is a reminder that the Ebo Forest provides a globally unique habitat and that the loss of even one of the hundreds of rare species would be a tragedy.

Original link:

https://www.rewild.org/news/rare-crab-species-rediscovered-in-ebo-forest-after-more-than-a-century

To help build ecological civilization and thoroughly implement the "Outline of the National Science Literacy Action Plan (2021-2035)" and the "China Association for Science and Technology Science Popularization Development Plan (2021-2025)", as a national first-level society in the field of biodiversity, the China Biodiversity Conservation and Green Development Foundation will leverage the advantages of scientific research institutions and is committed to creating a socialized science communication work with comprehensive mobilization and participation by all people. In December 2021, it launched the "Green Association Biodiversity Science Popularization Mini Classroom" series.

The "Green Association's Biodiversity Science Popularization Classroom" is characterized by "popular science". It disseminates knowledge about wild animal and plant species and biodiversity that are currently threatened with survival, promotes the mainstreaming of biodiversity, and calls on all sectors to work together to protect biodiversity, protect the habitats on which human beings depend for survival, and build a beautiful home where people and nature live in harmony.

Translated by YJ Reviewed by Stan