Salmonoid fish bdellosis is caused by leech-like ectoparasites in the monogenetic order Acanthobdellida. Although Acanthobdella species have been known to infect several threatened species in Eurasia, little is known about their ecology and epidemiology. In this paper, we report on the mass affection (up to 70.7%) of fish in lower course of the Chechuj River, a right tributary of the Lena and provide information on finding Acanthobdella peledina on two of six salmonoid fish species inhabiting there: lenok and grayling. New and more specific data on morphological peculiarities and feeding strategy were obtained. The ratio of body length to width in studied acanthobdellid collection is significantly less than one provided for the A. livanowi and the rest A. peledina from other water systems of Eurasia. Biology and lifestyle of the parasite population are revealed for the first time.
The first metagenomic analysis of the microbiome of the first sample of diseased endemic sponge Lubomirskia baicalensis (Pallas, 1771) from Lake Baikal and the comparison of the results with data published earlier on the microbiome of healthy sponges were carried out. Essential changes in the composition and structure of the microbial community were detected in the diseased individual possessing an uncharacteristic pink coloring. Cyanobacteria were predominant in the community, the fraction of the representatives of Ver rucomicrobia was increased. The diversity and number of eukaryotic algae, as well as of representatives of Bacteroidetes, Proteobacteria, Actinobacteria, and Planctomycetes, were decreased. A wide range of minor phyla were eliminated. The factors affecting the composition of symbiotic communities in sponges were con sidered. It was supposed that changes in the structure of symbiotic communities resulting in mass disease and death could be caused by an increase in the methane concentration in the water column of Lake Baikal.
The procedure, capabilities, and applicability limits of digital holographic video for the determination of the velocity and reconstruction of the trajectory of motion of plankton species in the habitat are considered. Results of experimental investigations of zooplankton in laboratory conditions are presented. Two species that differ by the morphology and sizes are examined, including Epischura baicalensis for the trajectory construction and Daphnia magna for an experiment on dual-view hologram recording. The position of a plankton species in the examined volume is suggested to be determined based on the coordinates of the center of gravity of its holographic image. Preliminary results of recording of a dual-view digital holographic video of plankton species are discussed.
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