Two New, Rare Freshwater Mussel Species Discovered

Sep 7, 2021 by News Staff / Source

An international team of scientists has discovered two new species of freshwater mussels endemic to the island of Borneo and established a new genus for them.

Khairuloconcha lunbawangorum and Khairuloconcha sahanae. Image credit: Zieritz et al., doi: 10.1002/aqc.3695.

Freshwater mussels are a crucial part of many freshwater habitats globally.

They live on the bottom of all kinds of freshwater habitats, where they filter algae, bacteria and other organisms from the water, thereby acting as biological filters and playing a major role in nutrient cycling.

They can remove algae, bacteria and other material at a rate of about one liter of water per hour per mussel.

Much of this material is subsequently transported to the benthos (organisms living on the bottom of the habitat), providing food for insects and other invertebrates, which thrive in mussel beds in terms of both abundance and diversity.

The island of Borneo has an exceptionally high number of freshwater mussels, with 15 of the 20 currently recognized native species being restricted to the island.

The two new species, named Khairuloconcha lunbawangorum and Khairuloconcha sahanae, are known from the basins of Limbang and Kinabatangan rivers, respectively.

“The new species are very rare, known only from a single site each (one in Sarawak, one in Sabah), and highly threatened by ongoing habitat destruction,” said Dr. Alexandra Zieritz, a researcher in the School of Geography at the University of Nottingham and the School of Environmental and Geographical Sciences at the University of Nottingham Malaysia Campus.

“One of these species is at especially high risk of extinction, as the only site it’s known from has already been dedicated for an industrial oil palm plantation.”

“We are in the process of preparing the paperwork with the University of Malaysia Sarawak to get this area protected.”

“This would not only help the unique biodiversity in this area but also the indigenous Lun Bawang tribe after which we named that species, Khairuloconcha lunbawangorum.”

The declines of existing populations of freshwater mussels on Borneo have likely been caused by industrial-scale deforestation and land-use change from primary rainforest to agricultural monocultures (predominantly oil palm plantations).

“These practices result in high levels of soil erosion, strongly increasing sediment yield (amount of sediment run-off), and organic and inorganic pollution (via agricultural run-off) of rivers, all of which negatively affects freshwater mussels directly, by degrading habitat quality, or indirectly by reducing host fish populations that they require to complete their life cycles,” the researchers said.

“Other potential drivers of declines in Borneo’s freshwater mussel populations include pollution from domestic and industrial sewage, hydrological alterations, mining, climate change and invasive species.”

The study appears in the journal Aquatic Conservation.

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Alexandra Zieritz et al. A new genus and two new, rare freshwater mussel (Bivalvia: Unionidae) species endemic to Borneo are threatened by ongoing habitat destruction. Aquatic Conservation, published online September 3, 2021; doi: 10.1002/aqc.3695