By Manila, Philippines – Mona Gonzalez
We must safeguard the web of life and care about the other living species that we share this planet with. Pygmy tarsiers eat and host bugs that we’ve seen at home — insects, spiders, lizards, bedbugs, lice, fleas, roundworms, and tapeworms. The vaquita is preyed upon by large sharks and killer whales, keeping them away from us. But only 10 vaquitas are left and in their absence, the diet of sharks and whales may change. A tiger in the wild indicates that the forest it inhabits is healthy and diverse. As of now, there are 3,900 tigers in the wild globally, and more than twice as many (8,000) in captivity. By protecting the web of life, we build a kinder world for everyone.
After 66 years of being unseen, it was largely believed by scientists that the rainbow-colored, freshwater Sierra Leone Crab (Afrithelphusa leonensis) was extinct.
It was last spotted in 1955, when Sierra Leone was a British Protectorate. At that time the crabs were found in Sugar Loaf Mountain, which is the highest point in the country’s Western Area Peninsula, and where the capital city, Freetown, is located. Three crabs were taken as samples.
It’s likely that these crabs informed a 350-page monograph that was written by BOTI (1955, 1959. 1964, 1969b. 1970a,b), who has done “the most comprehensive works on the taxonomy of the freshwater crabs of Africa” according to Prof. Neil Cumberlidge of Northern Michigan University, who is also chair of the International Union for Conservation of Nature’s (IUCN) Freshwater Crustacean Specialist Group.
It was in February 2021 that the multicolored Sierra Leone crab was found again. Due to COVID, Cumberlidge collaborated online with Pierre A. Mvogo Ndongo, who did the vital footwork, and who is also a member of the IUCN group. Mvogo Ndongo is also a lecturer and researcher from the Department of Management of Aquatic Ecosystems, Institut des Sciences Halieutiques, of the University of Douala in Cameroon.
Prof. Cumberlidge has successfully described 14 new genera and identified more than 67 new species of crabs. He and Prof. Mvogo Ndongo are two of only three global experts of West Africa’s unusual freshwater crabs.
Cumberlidge, who was formerly Mvogo Ndongo’s doctoral advisor, prepared the original proposal to rediscover Sierra Leone’s colorful crab. A grant was given by Re:Wild, an environmental group that actor Leonardo DiCaprio helped to found with a group of conservation scientists. Re:Wild’s goal is to conserve and fully re-establish the original biodiversity of plant and animal life on Earth.
Because of COVID-19, Cumberlidge was forced to stay behind. Mvogo Ndongo, did the critical legwork, while Cumberland was the online consultant. Mvogo Ndongo traveled to Sierra Leone and stayed for 23 days, traveling throughout the country’s forested areas.
It was hard work, which required that Mvogo Ndongo remain psychologically strong and determined. He learned from his errors. For example, he initially asked locals if they’d seen crabs on land. They led him to many water crabs that sometimes walk on the ground. He changed his strategy and asked if they’d seen forest crabs that only live on land, far from bodies of water. This resulted in the discovery of three freshwater crab species, two of which were discovered for the first time, and a third crab species, the Afzelius’s crab, which had not been seen for 225 years and was long deemed extinct.
Cumberlidge said, “All of the crabs he collected were photographed and emailed to me for identification. Then I would tell him where to look next. This is how we worked it (out) for the three weeks he was in the field.”
Despite the wonderful success of Mvogo Ndongo’s trip, he had yet to discover the actual crab that they were looking for, the Sierra Leone crab. It was on the last four days of his trip that they were found.
Mvogo Ndongo discovered the crab by enlisting the help of some young people whom he motivated by explaining the benefits of being involved in the project. The young people spoke the dialect of the locals and as a group, they weathered through many undefined paths and steep slopes in Sugar Loaf Mountain. The mountain has spaces of undefined paths, abysmal forestry, a steep, sharp rock stretch, and a hill that almost seems to stand erect. It was not a climb for the weak-minded.
His persistence paid off, and Mvogo Ndongo managed to find six crabs. The Sierra Leone crabs were living in the forest’s belly, far from developed areas. They were hidden so deep underground that Mvogo Ndongo and his team had to work very carefully, so as not to harm them while digging them up. They used a pick and machete mindfully, and the process was slow and tedious.
Finally, they unearthed the crabs, which were covered with dirt and grime. Mvogo Ndongo and his team cleaned the crabs until their brightly colored shells shone. They then photographed the crabs and the pictures were sent to Cumberlidge, who confirmed the species.
Mvogo Ndongo told Re:Wild, “When I found the Sierra Leone crab, I was very very happy. This was after almost three weeks of searching for (the) lost species.” In his entire search, he’d visited nine remote locations in the northern, southern, southeastern, and Western parts of Sierra Leone, combing the most difficult parts of the varied forests. He also went to Western Area National Park, Guma Lake, and the far-reaching forest beyond the Lake, before he found the Sierra Leone crabs in Sugar Loaf Mountain.
With these findings, both Cumberlidge and Mvogo Ndongo wrote their expedition report. They are also working jointly on a paper describing their new discovery of the Afzelius crab, which hadn’t been seen in 225 years. Plus, they plan to meet in Berlin, Germany to write about the two new species that Mvogo Ndongo found in the forest.
Here are some facts about the Sierra Leone crab:
- The Sierra Leone crab (Afrithelphusa leonensis) has a bright body and is very colorful. The female Sierra Leone crabs have slightly purple-hued bodies and speckled orange claws. The male’s claws are a blend of purple-pink, with orange legs.
- It is one of five known African land crab species.
- Land crabs tend to be far more colorful than water-dwelling crabs,
- This crab is endemic to Sierra Leone, and it doesn’t spend time near water.
- It lives in the crevices of rocks, or in the hollows of trees, or burrows deep beneath the forest floors. Its home is far away from any permanent water source.
- The IUCN ranked this crab as “Data Deficient” before the six new crabs were discovered.
- The IUCN said information is needed requiring its habitat requirements, long-term threats, population size, and community trends. With the rediscovery of this crab, conservationists have learned more, causing the IUCN to now rank the Sierra Leone crab as “Critically Endangered”.
- Freshwater Sierra Leone crabs have specialized breathing structures that allow them to breathe air.
- There are only five species of land crabs, all rare, in African countries like Sierra Leone, Guinea, and Liberia.
- In general, freshwater crabs can be found in all of Africa’s major ecosystems. However, they are most abundant in rainforest highlands.
Threat of extinction
According to Cumberlidge, the discovery of the Sierra Leone crab is bittersweet because although the crab is not extinct, it remains critically endangered. Because of this, conservation interventions are urgently needed for their long-term protection as a species.
Cumberland said the crab and other forest creatures are at “immediate threat” due to incursions into its habitat by people, who engage in both small and large scale deforestation. This destruction will be exacerbated as the human population grows.
“Even the Western Area Peninsula National Park (in the forests of Sugar Loaf Mountain), where the Sierra Leone crab was rediscovered is not as protected as it should be,” Cumberlidge said. Although the forest area is largely intact, agriculture is starting to encroach upon the borders.
Moves toward conservation
Cumberlidge and Mvogo Ndongo will collaborate with the IUCN’s Freshwater Crustacean group, which includes specialists worldwide who are interested in conserving aeglids (freshwater crustaceans), freshwater crabs, crayfish, and shrimps.
He adds that he is certain that Mvogo Ndongo discovered a healthy group of crab species, which ensures them the opportunity to collect data and to more closely study the behavior and ecology of the crab. They also want to keep track of its numbers.
The new data will also enable the IUCN to reassess the Red List status of this crab. It is highly likely that the crab will be considered to be Critically Endangered (meaning close to extinction).
Cumberlidge told Mongabay, “What makes them vulnerable to extinction is their rarity. They are both narrow in range and an endemic species, found in just a small area and nowhere else in the whole world, which makes them both hard to find and vulnerable to threats that wipe them out completely.”
Once they learn the above, including the areas where the crab dwells, a species-specific action plan will be drawn geared to community education, natural environmental protection, breeding programs, and other efforts so their populations can thrive. To make this happen, they will also enlist the help of conservationists from Sierra Leone.
The Ecological Role of the Sierra Leone Crab
What ecological role does the Sierra Leone crab play? Cumberlidge told Pressenza,
“This freshwater crab species is a member of the tropical rainforest community – its ecological contribution to the food web may be complex because it is an aquatic animal (a crab) whose relatives are adapted to stream and river life, which seems to be semi-terrestrial (we never found it in water). The place where it lives, on the forest floor, groups it with terrestrial communities because the burrows it digs are sited far away from permanent water sources.”
Cumberlidge adds, “Although this species is new to us, we know that other African freshwater crabs are opportunistic feeders, being both omnivores and scavengers, eating vegetable matter as well as animals (mainly invertebrates), either dead or alive.”
He also pointed out its possible work as recyclers noting, “Some studies have even suggested that freshwater crabs are general scavengers eating plant-derived detritus and belong to the shredder guild, picking up vegetation and reducing it to fine particles which then cycle around the food web.”
Role of the Sierra Leone crab in the Foodchain:
In terms of the freshwater crab’s role in the food chain, Cumberlidge told us, “Freshwater crabs in West Africa are the favorite food of mammals associated with aquatic habitats (such as civets, otters, and mongooses), but are also eaten by large waterbirds (e.g., eagles, herons, storks, kingfishers, and egrets), large reptiles and amphibians (young crocodiles, water monitors and frogs), and predatory fish (e.g., catfishes).”
As for the freshwater crab’s diet, Cumberlidge told Pressenza, “Freshwater crabs have an essentially herbivorous and detritivorous diet, so at this point, we assume that the Sierra Leone Crab also has this diet.”
A world without the Sierra Leone crab
What would the world be like without the Sierra Leone crab? Cumberlidge notes, “We thought for years that they might actually be extinct (given the lack of sightings and the large-scale destruction of their rainforest habitat), and quite honestly, this thought did not seem to have much of an effect on humanity and the world!”
He cites, however, the economic and possible medical role that freshwater crabs play, saying, “Freshwater crabs have economic importance (people eat them) and medical importance (they host and transmit the parasites that cause human lung fluke disease, and help the vectors of the parasite that causes river blindness).”
He cautions, however, that “It is too early to say whether these lost species have any medical importance, and we still don’t know whether they form a significant part of the diet of humans living in the forest.”
Cumberlidge told Pressenza that a positive result of the rediscovery of these crabs is, “Given that none of the 1500 species of freshwater crabs worldwide are known to be extinct on the IUCN Red List, these ‘Critically Endangered, Possibly Extinct’ species have now avoided this unwanted title for now.”
The broad perspective
Cumberlidge adds, “From a broader perspective, this is a question that is seeking justification for saving species beyond their obvious intrinsic interest and beauty. One answer would be the ecological importance of large invertebrates to the provision of ecosystem services that are provided by intact forest ecosystems that need all members of the food web for the system to function sustainably and provide free ecosystem services (e.g., clean water, air, sustainable forest products, stabilization of soils, etc.).”
The human threat
People pose a major threat to these African freshwater crabs. People are blamed for water and land pollution, mining, agriculture, industrial development, hydroelectric power, drainage, and deforestation.
And people have experienced the consequences of the abovementioned. On August 14, 2017, intense rainfall caused a mudslide to occur on Sugar Loaf Mountain, which led to giant sinkholes and floods. Concrete houses that were built on the mountainside were destroyed. A World Bank report that was released one month after the disaster said some 6,000 people were affected, and some 1,141 people were either dead or missing. One may view it as the worst natural disaster in Sierra Leone’s history.
We must bear in mind that we share this earth and we don’t own the planet. By being mindful of other living creatures including animals, plants, and ecosystems, we keep ourselves safe even as animals, the forests, and other living things can do what they do to make our planet a true home that is safe and healthy for all.
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