Orthoseira variabilis sp. nov., , a new diatom from a snow patch in Potter Cove, King George Island, Antarctica

A new species of diatom, Orthoseira variabilis sp. nov., is described here based on snow samples collected in Potter Cove area, King George Island/Isla 25 de Mayo, Antarctica. The new taxon was characterized by using light and electron microscopy. The proposed specific epithet "variabilis" refers to the high variability in several morphological features exhibited and so far not reported in other species of the genus, such as marginal spines present or absent, areola openings surrounded by small spinules or by a complete silica ring, caverns at the valve face/mantle junction shallow or sometimes inconspicuous, and internal slits between the carinoportulae variably developed. Contrary, all characters of the girdle elements such as arrangement of poroids, presence of fimbriae and ligula, and valvocopula internal thickening are constant. The morphology of O. variabilis is compared to similar species and brief comments on the ecology of this taxon and the associated diatom flora are also presented. This is the first Orthoseira species established from Antarctica and from a sympagic environment.