Balasubramanian Karthick

Two new species ofNitzschia(Bacillariophyceae) from freshwater environs of Lonar Crater Lake, India: Two newNitzschiafrom India

Diatom taxa in India were first documented by Ehrenberg and subsequently many studies have focused on the Western Ghats and Himalayan mountains while other regional environments were rarely explored. In the current study, the freshwater environs of the saline Lonar Crater Lake were investigated and two new Nitzschia species have been described. Nitzschia kociolekii sp. nov. and Nitzschia tripudio sp. nov. were sampled from bird feeding ponds associated with Lonar Lake. The morphological characters of the new species are similar to N. amphibia and N. frustulum but differ in terms of striae pattern, polymorphic areolae development, fibula and stria density. In addition, larger specimens of N. williamsii, a recently described taxon from Bangalore wetlands of Peninsular India, were found in a waterfalls flowing into Lonar Lake. All three taxa are freshwater diatoms and are possibly endemic to Peninsular India.

Four new Rhoicosphenia species from fossil deposits in India and North America

Rhoicosphenia Grunow is a common diatom in both freshwater and marine ecosystems and the genus can be found on nearly every continent. Most of the currently described taxa are extant and only six of 58 taxa are known from the fossil record. Also, reports from freshwater habitats of the Indian subcontinent are rare, with one report of Rhoicosphenia marina from marine ecosystems. Rhoicosphenia is common in freshwater and marine ecosystems of the USA and three fossils have been described from the Pacific Northwest. Four new species of Rhoicosphenia are described from fossil deposits in Gujarat, India and Oregon, USA. The new species from India are R. gandhii, a large, coarsely ornamented species and R. indica, a smaller species, both found in the same fossil deposit. The species from Oregon are R. reimeri, another large taxon, as well as R. patrickae, another small species, and both are found in the same fossil deposit. These new species descriptions highlight the recent trend of discovery of Rhoicosphenia diversity over the past decade. Finally, a discussion of the valvocopula structure in Rhoicosphenia is included with comparisons to septa and septum-like structures of other diatom genera.