TAXONOMY AND ULTRASTRUCTURE OF TWO NEW NEIDIUM SPECIES FROM LAKES IN THE SIERRA NEVADA MOUNTAINS OF NORTHERN CALIFORNIA (U.S.A.)

Abstract

Neidium Pfitzer is a common genus in the freshwater diatom flora of the United States. Most Neidium taxa are large diatoms with robust features. However, several smaller, more finely organized species are also present. These species are often overlooked in collections due to their size and finer structure. Upon reviewing collections from several lakes and rivers in Northern California, some new and interesting forms were discovered. In this work observations on two Neidium species are provided that appear to be new to science. The first species is zmoderately sized, has an undulate margin and a broad, rectangular central area. The second is small, linear in shape, and has very fine striae. Light and scanning electron microscope observations on these two species are presented on both valve and girdle components, and they are compared to other small, finely ornamented taxa. These observations suggest there are still many new species of freshwater diatom to discover and describe in the U.S. flora.