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World’s oldest lake holds world’s newest genus

05 April 2006

Natural History Museum scientists have discovered a new genus of diatom. Named Amphorotia, the genus contains 14 species, including six new to science.

Basis of the food chain

Diatoms (Bacillariophyta) are a group of single-celled algae that photosynthesise - a process that coverts sunlight into chemical energy used by animals. Diatoms live in marine and fresh water and are extremely important for many animals as they form the basis of the food chain on our planet.

The oldest lake

The new genus was first discovered living in Lake Baikal, Russia, but occurs elsewhere in the world.

Lake Baikal is the world's largest lake and holds nearly 20 per cent of the world's unfrozen surface fresh water. It has many endemic species - organisms not found anywhere else. This has been explained by the fact that at 20 to 30 million years old, it's the oldest lake in the world, and plants and animals have had plenty of time to evolve into new species.

Life at the deepest depths
Light micrograph of Amphorotia americana, an extinct diatom species living 15-20 million years ago.

Light micrograph of Amphorotia americana, an extinct species of diatom that lived in the USA and Japan in the Miocene, 15—20 million years ago.

Natural History Museum scientists Dr David Williams and Dr Geraldine Reid discovered the new genus while studying diatom diversity in Lake Baikal.

'This remarkable new find is really only the tip of the iceberg,' said Williams. 'The diatom diversity in Lake Baikal, especially in its deeper waters, is almost entirely unknown and unstudied.'

It is estimated that there are over 500 species of diatom found only in Lake Baikal. This number increases with each new biodiversity survey carried out making Lake Baikal home to one of the most diverse diatom communities in the world.

Living fossils

Species in the new genus Amphorotia are both fossil (extinct) as well as living; those found in deep lakes have been called living fossils, relics from the past still thriving in these unique and ancient habitats.

Five of the species are found only in Lake Baikal (two being new to science), one found only in Lake Khuvsgul (Hövsgöl), Mongolia, four only in southeast China and three are believed to be extinct, known only from Miocene (15-20 million years ago) fossil specimens.

Unusual distribution

The geographic distribution of the species is somewhat unusual, showing two contrasting patterns, one extending across the cold northern hemisphere, the other south towards the tropical regions of southeast Asia via southern China. Williams and Reid are now researching why this diatom distribution is the way it is.

'This study highlights the need to understand these unique habitats and track what species are actually on the planet before they disappear forever in these times of dramatic species loss through extinction' said Reid.

Williams and Reid have produced a major monograph, or book, Diatom Monographs, which provides detailed light and electron microscope images of all 14 species.

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