Two new species of the diatom genus Meridion (Bacillariophyta, Tabellariaceae) from Aleutian Islands

Abstract

Two new species of Meridion (Bacillariophyta, Tabellariaceae) are described from Unalaska Island (Aleutian Islands, USA) based on light and scanning electron microscope investigations. Meridion tenuipes sp. nov. is characterized by very slender valves with capitate headpole, lack of costae at the footpole and rimoportula positioned close to valve apex. Meridion humerosum sp. nov. possesses more robust valves with capitate poles, separated by distinct shoulders, costae distributed through the whole valve length and rimoportula displaced some distance from the apex. Comparison of these new species with other heteropolar representatives of the genus is provided. Our data indicate that the degree of Meridion endemism in North America is even higher than it was previously supposed.