Sunday, 3 November 2013

Three new species of Diatom from Mountain Lakes in Washington State, USA.

Diatoms are single celled algae related to Kelp and Water Moulds. They are encased in silica shells with two valves. During reproduction the cells divide in two, each of which retains one valve of the shell, growing a new opposing valve, which is slightly smaller and fits flush within the older valve. This means that the Diatoms grow smaller with each new generation, until they reach a minimum size, when they undergo a phase of sexual reproduction, giving rise to a new generation of full-sized cells.

In a paper published in the journal Phytotaxa on 29 August 2013, Mihaela Enache and Marina Potapova of the Academy of Natural Sciences in Philadelphia and Rich Sheibley and Patrick Moran of the United States Geological Survey describe three new species of Diatoms from oligotrophic (nutrient poor) and ultraoligotrophic (very nutrient poor) alpine lakes in the Olympic and Cascade Mountains of Washington State, USA. All three species are placed in the existing genus Psammothidium, and were described as part of a study into the Diatom flora of these environments, with the aim of using them as biomarkers when studying ancient sediments from the region.

The first new species described is named Psammothidium lacustre, implying a lake dweller. Psammothidium lacustre is a 16.7–28 μm elliptical Diatom, with elongate rows of areolae (holes through which the organism obtained nutrients) on either side of a central axis running lengthways on each valve, and a central raised area.

Psammothidium lacustre (Top left). External view of valve from Hidden Lake. (Top right). Internal view of valve. (Center left). Areolae on internal surface of valve. (Bottom left). Internal view of valve from Hidden Lake. (Bottom right). External view of valve. Scale bars are 1 μm. Enache et al. (2013).

The second new species described is named Psammothidium alpinum, a reference to the alpine lakes where it was discovered. Psammothidium alpinum is a 14.6–30 μm oval Diatom, with elongate rows of areolae (holes through which the organism obtained nutrients) on either side of a central axis running lengthways on each valve, and a central raised area.

Psammothidium alpinum. (Top left). External view of valve. (Center left). Internal view of valve. (Top right). External view of valve. (Bottom right). Internal view of valve, Hidden Lake. (Bottom left). Areolae on the internal surface of the valve, Snow Lake. Scale bars are 1 μm. Enache et al. (2013).

The final new species is named Psammothidium nivale, in reference to the site where it was first discovered, Snow Lake (nivale means winter in Latin). Psammothidium nivale is a 11.7–15 μm elliptical Diatom, with elongate rows of areolae (holes through which the organism obtained nutrients) on either side of a central axis running lengthways on each valve, and a central raised area.

Psammothidium nivale. (Top left). External view of valve. (Bottom left). Internal view of valve. (Top right). External view of valve. (Bottom right). External view of valve, Hidden Lake. Scale bars are 1 μm. Enache et al. (2013).

See also Four new species of fossil Diatom from the western United StatesA Late Miocene-Pliocene Diatom redescribed from Scanning Electron Microscope images and New species of Diatom from Japan.

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