S. I. Genkal

CYCLOTELLA MELNIKLAE SP. NOV., A NEW DIATOM FROM THE MOUNTAIN LAKES OF PRIBAIKALIE, RUSSIA

During phytoplankton studies of the mountain lakes of the Dzherginsky Nature Reserve situated East of Lake Baikal, Siberia, a new species of centric diatom was discovered, Cyclotella melnikiae Genkal et Bondarenko sp. nov. Its morphology is described using light and scanning electron microscopy. Cyclotella melnikiae is similar to Cyclotella tripartita Hakansson, Cyclotella rossii Hakansson, Cyclotella kuetzingiana Thwaites and Cyclotella chantaica Kuzmina et Genkal but is distinguished from them by the location of the rimoportulae on the valve face.

Aulacoseira konstastinovii sp. nov. and Aulacoseira krylovii sp. nov. – two new centric diatoms from South-east Asia

Two new centric diatom species were found in samples collected from Vietnam and Cambodia, Aulacoseira konstantinovii sp. nov. and Aulacoseira krylovii sp. nov. The former differs from other members of the genus mainly by a characteristic strong undulation in the central area of the valve face. The latter is close to A. konstantinovii sp. nov. but differs in its valve face morphology and having fewer rimoportulae. The new species are illustrated by light microscope and scanning electron microscope images.

Morphology and distribution of the North American diatom Aulacoseira pardata English & Potapova in Russia

Diatom species Aulacoseira pardata English & Potapova, new for the flora of Russia, has been found in the course of studying samples from Lake Frolikha (Transbaikal region) by scanning electron microscopy. Numerical morphological features of the species in the studied population differ from the type population, which indicates their greater variability. It is shown that A. pardata is distinguished from the similar species A. septentrionalis (Camburn & Charles) Genkal & Kulikovskiy by the shape of spines and shape and size of areolae on the valve mantle. Species A. septentrionalis, new for the lake, as well as for Cis-Baikal and Transbaikal regions, has also been recorded in Lake Frolikha.

Morphology and distribution of Cymbella neocistula Krammer and Cymbella nepalensis (Jüttner & Van de Vijver) Vishnjakov stat. nov. (Bacillariophyceae) in water ecosystems of South Siberia and Mongolia

The valve morphology of taxa from the Cymbella cistula group from different water ecosystems of southern Siberia (Russia) and northwestern Mongolia is investigated. Two species with similar morphology, C. neocistula Krammer and C. nepalensis (Jüttner & Van de Vijver) Vishnjakov stat. nov., are found. C. nepalensis differs from C. neocistula by valve outline and a usually higher number of stigmata on the central area. The morphological variability of species from C. cistula complex, their ecology, and distribution are discussed.

Comparative morphological characteristic of diatoms of genus Hannaea Patrick of the two largest lakes of the Baikal rift zone with a description of the new species

The comparative morphological characteristics of fragilaroid diatoms of genus Hannaea from lakes Baikal and Khubsugul, based on the results of light and electron microscopy, as well as new data on the study of type material H. baicalensis in a light microscope, are shown. New species H. hovsgolensis Vishnjakov, Kulikovskiy et Genkal from Khubsugul Lake is described. H. hovsgolensis has high similarity with H. baicalensis based on the presence of a biseriate striae and bilabiate rimoportulae on both ends of valves. These features are characteristic for species of the Baikal rift zone and determine their difference from Holarctic species: H. arcus and H. inaequidentata.

Stephanodiscus popovskayae, a new species from the volcanic lakes of Kamchatka in East Asia, Russia

During phytoplankton studies of the volcanic lakes of Kamchatka in East Asia, Russia, a new centric diatom species was discovered, Stephanodiscus popovskayae sp. nov. Its morphology is described using light and scanning electron microscopy. Stephanodiscus popovskayae occurs mainly in small colonies and its valve face is concentrically wavy to almost flat, with one (rarely two) central fultoportulae. Stephanodiscus popovskayae is similar to S. chantaicus Genkal & Kuzmina. The main difference is the lack of central fultoportulae in S. chantaicus.

On the morphology and taxonomy of Parlibellus Crucicula (Bacillariophyta)

A study of the phytoplankton of the water bodies and watercourses in the Yarayakha River and Naduiyakha River basins (the Yamal Peninsula) has revealed a wide morphological variability of the quantitative diagnostic features in Parlibellus crucicula: valve length and width, the number of striae and areolae in 10 μm, and the stria density in the middle part of the valve. A number of the features (raphe structure, presence of pseudosepta, and obliquely oriented oval areolae) typical for the genus Prestauroneis have been found in Parlibellus crucicula. This makes it possible to define this species as belonging to the genus Prestauroneis and to form a new combination, Prestauroneis crucicula (W. Smith) Genkal et Yarushina comb. nov.

Morphological investigation and transfer of Naviculadicta parasemen Lange-Bertalot to the genus Rexlowea Kociolek & Thomas

We document the size diminution series and valve morphology of the diatom Naviculadicta parasemen Lange-Bertalot in Lange-Bertalot & Genkal, described originally from the Yugorsky Peninsula and nearby islands, northwest Siberia. Based on material from the northeastern Arctic, the features of the valve structure, undulate raphe with dilated external proximal raphe ends, organization of the striae, and change in orientation of the striae near the apices suggest a close affinity with the monotypic genus Rexlowea. We effect the transfer of N. parasemen to Rexlowea, making the new combination R. parasemen. Several features of R. navicularis, the generitype, are missing from R. parasemen, including septa and pseudosepta. It may therefore be necessary to emend the description of Rexlowea as additional species are referred to the genus, but we will await discovery of additional species before formal emendation.

To ecology and morphology of Thalassiosira incerta Makarova (Bacillariophyta)

Thalassiosira incerta has reached an appreciable level of quantitative development in the Cheboksary Reservoir and Oka River (hundreds of thousands and millions of cells per liter, from tenths to tens of grams per cubic meter). Higher abundance and biomass of this species are recorded during the low-water period (August). Algal bloom, to the extent typical for eutrophic/hypertrophic waters, is observed in the Oka River in its section with a typical river regime which is not subjected to the reservoir’s backwater effect. Our studies make it possible to specify the ecology, range, and morphological features of the species. River conditions of highly trophic and highly saprobic water courses during dry years of the vegetation period are optimal for species development.

Materials on the flora of Bacillariophyta in rivers of the white sea basin in the Republic of Karelia

A total of 290 species and varieties of Bacillariophyta including 32 that were new for the flora of Karelia and 18 that were new for the flora of Russia, have been recorded in phytoplankton in nine rivers of the White Sea basin. The genera Aulacoseira, Pinnularia, Eunotia, and Navicula s. l. are the richest in taxonomy. The maximum species diversity was recorded in the Suma (73), Kolezhma (91), and Chirko-Kem (146) rivers. The following species are the most widespread in the rivers that were under study here: A. ambigua, A. subarctica, A. subborealis, {tiA. tenella}, Asterionella formosa, and Tabellaria flocculosa.