Petrology of alkaline silicate rocks and carbonatites of the Chuktukon massif, Chadobets upland, Russia: Sources, evolution and relation to the Triassic Siberian LIP

The petrogenesis of temporally and spatially associated carbonatitic and deeply derived carbonated alkaline silicate magmas provides an opportunity to gain insights into the nature of the deepest lithospheric mantle. The Chuktukon massif, which is part of the Chadobets alkaline ultramafic carbonatite complex (Chadobets upland, Siberian craton) is a carbonatite-melilitite-damtjernite intrusion, whose emplacement was coeval with the Siberian Traps large igneous province (LIP). In this study, the sources of the primary melts are examined, the petrogenetic evolution of the complex is reconstructed and the relationship with the Siberian LIP is also discussed. Isotopic and geochemical information indicate that the source for the Chuktukon primary melts was isotopically moderately depleted and the primary melts were formed by low degree partial melting of garnet carbonated peridotite. Hydrothermal processes caused 18O- and 13C- enrichment. The weathering process was accompanied by trace element re-distribution and enrichment of the weathering crust in Zn, Th, U, Nb, Pb and REE, relative to the Chuktukon rocks and a change in radiogenic (Sr, Nd) isotope compositions

Some Aspects of Development and Histological Structure of the Visual System of Nothobranchius Guentheri

In this, work some aspects of the development of the visual system of Nothobranchius guentheri at the main stages of ontogenesis were described for the first time. It was possible to establish that the formation of the visual system occurs similarly to other representatives of the order Cyprinodontiformes, but significantly differs in terms of the individual stages of embryogenesis due to the presence of diapause. In the postembryonic period, there is a further increase in the size of the fish’s eyes and head, to the proportions characteristic of adult fish. The histological structure of the eye in adult N. guentheri practically does not differ from most teleost fish living in the same environmental conditions. The study of the structure of the retina showed the heterogeneity of the thickness of the temporal and nasal areas, which indicates the predominant role of peripheral vision. Morphoanatomical measurements of the body and eyes of N. guentheri showed that their correlation was conservative. This indicates an important role of the visual system for the survival of fish in natural conditions, both for the young and adults. In individuals of the older age group, a decrease in the amount of sodium (Na) and an increase in magnesium (Mg) and calcium (Ca) were found in the eye lens. Such changes in the elemental composition of the lens can be a sign of the initial stage of cataractogenesis and disturbances in the metabolism of lens fibers as a result of aging. This allows us to propose N. guentheri as a model for studying the structure, formation, and aging of the visual and nervous systems

Petrography, mineralogy and SIMS U-Pb geochronology of 1.9–1.8 Ga carbonatites and associated alkaline rocks of the Central-Aldan magnesiocarbonatite province (South Yakutia, Russia)

The N-S trending Central-Aldan magnesiocarbonatite province is located in the Aldan-Stanovoy shield (South Yakutia, Russia). Several apatite-dolomitic carbonatite occurrences were studied: Seligdar, Muostalaah, Ust-Chulman and Birikeen. Mineralogical and petrographic investigations indicate intense hydrothermal-metasomatic alteration and metamorphism, which are reflected in the evolution of the mineral parageneses. The primary minerals are fluorapatite, magnetite, ilmenite, dolomite, K-feldspar, phlogopite and accessory zircon, titanite, baddeleyite and thorite. The hydrothermal-metasomatic minerals are quartz, calcite and siderite aggregates with haematite, monazite-(Ce), xenotime-(Y), rutile-(Nb), barite-(Sr), anhydrite, ancylite-(Ce) and rare sulphide mineral phases. Alkaline rocks associated with the Muostalaah complex, were also studied. The following U-Pb ages have been obtained (Ma): 1930 ± 7 for Muostalaah alkaline basic rocks, 1906 ± 6 for Muostalaah carbonatites, and 1880 ± 13 and 1878 ± 17 for Seligdar and Ust-Chulman carbonatites, respectively

Evaluation of Age-Dependent Changes in the Coloration of Male Killifish Nothobranchius Guentheri Using New Photoprocessing Methods

Fish as model objects have found wide applications in biology and fundamental medicine and allow studies of behavioral and physiological responses to various environmental factors. Representatives of the genus Nothobranchius are one of the most convenient objects for such studies. Male fish belonging to the family Nothobranchiidae are characterized by extremely diverse coloration, which constantly changes, depending on the age of the fish, environmental factors, and social hierarchical status. These fish species are characterized by a short life cycle, which allows changes in coloration, an indicator of the ontogenesis stage, to be estimated. Existing methods of fish color assessments do not allow the intensity of coloration of particular body zones to be clearly differentiated. In the present study, we suggest a method of two-factor assessment of specific fish body zones using modified methods of photofixation and image processing software. We describe the protocol of the method and the results of its application to different-aged groups of male Nothobranchius guentheri. The coloration of selected areas (i.e., red spot on the gill cover (RSGC), black border on the caudal fin (BBCF), and white border on the dorsal fin (WBDF)) differed significantly according to the size and age of the fish (p N. guentheri can be a model for studying aging by the intensity of body coloration in males