The article considers studying the physiological and biochemical parameters of the common sprat (Clupeonella delicatula caspia Svetovidov) taken in the western part of the Middle Caspian Sea at different periods of the annual cycle. There were studied the species in the pre-spawning state, at the beginning of spawning, at the feeding stage and at the pre-wintering stage. In fish muscle tissue the content of water-soluble protein and total lipids was determined. In the pre-spawning period, in male common sprat was recorded a positive correlation (p < 0.05) between the weight of fishes, fishing length and content of total lipids in muscles (r = +0.5206) and (r = +0.5039), respectively. In females no statistically significant dependence of the size-weight parameters and lipid content in muscles were recorded, which is probably due to the fact that lipids in their bodies were spent for energy needs, and to a greater extent than in males - for the generative function. In a comparative aspect, in the muscles of males and females no significant differences in the content of total lipids and water-soluble protein in the pre-spawning period were found. At the stage of the beginning of spawning, a decrease in total lipids and water-soluble protein was noted in the muscle tissue of the studied fishes, which is associated with an increase in energy consumption for sweeping out sexual products. During the feeding period the common sprat was characterized by an intensive accumulation of lipid reserves; the content of total lipids and water-soluble protein in the muscles increased with increasing length of individuals. In the pre-winter period stabilization of muscle lipid and increase in protein reserves were recorded, which is necessary for fish to ensure a normal existence in the subsequent stages of the annual cycle.
For the first time, a study of genetic variability of Caspian anadromous herring was carried out using molecular genetic methods. Sequencing of the cytochrome B site of mitochondrial DNA allowed to identify 7 haplotypes. The most massive haplotype was Hap_Alosa1 noted in 29 herring individuals. Five minor haplotypes were detected in few fish individuals. In the marine period of life in fish caught in the Northern Caspian there were noted rare haplotypes Hap_Alosa6 and Hap_Alosa7. In the river period of life in the Volga herring there was observed Hap_Alosa5. The revealed polymorphism of haplotypes was represented by single nucleotide substitutions. The genetic analysis of migratory herring does not give grounds for isolating the studied fish into separate groups. The marked low level of nucleotide diversity of cytochrome B gene of mitochondrial DNA of the anodromous herring indicates a significant genetic homogeneity of the species within the studied range. The results of analysis of nuclear DNA microsatellite loci showed that only three of the six sites of the studied gene were polymorphic. In individuals caught in the river period of life, only Af20 (out of the 6 loci studied) was polymorphic and was characterized by 4 alleles. In a sample of herring from the Northern Caspian, 3 polymorphic loci (Aa16, Af6 and Af20) were observed, in which 2 alleles were recorded. The observed heterozygosity varied from 0.313 to 0.667 exceeding the level of expected heterozygosity. In polymorphic loci a deficit of heterozygotes was not noted. The results obtained in this study indicate a low level of genetic variation of anadromous herring.
The paper outlines the study of the physiological and biochemical parameters of golden mullet (Liza aurata, Risso) in the Caspian Sea. Collecting material was carried out in the western part of the Northern and Middle Caspian in September-October 2019. The female and male species were analyzed. The histomorphological investigation of the gonads of females and males indicated the completion of spawning. The morphological picture of the gonads of golden mullet of both sexes corresponded to the maturity scale of this species as applied to the Caspian region. In the blood there was determined the concentration of hemoglobin, total serum protein, total lipids, triglycerides, cholesterol, glucose, and inorganic phosphorus. A valid positive correlation dependence (p < 0.05) of weight and length of females (r = 0.9340) and males (r = 0.9320) was stated. In females high correlations were recorded between the levels of total serum protein and cholesterol (r = 0.9071), total serum protein and hemoglobin (r = 0.9706), glucose and hemoglobin (r = 0.8897) with a statistical significance level of p < 0.05. The revealed statistical dependencies of physiological and biochemical parameters of fish blood indicated their important role in the body in optimizing the total energy costs after spawning. According to the study of males, there has been found a high (r = 0.9195) significant (p < 0.05) correlation relationship between the content of hemoglobin and cholesterol in the blood. The content of total lipids in muscles, gonads and liver of females and males of golden mullet were comparable. The levels of water-soluble protein in the muscles, liver, and gonads of fish of both sexes did not differ significantly. The obtained research results on the complex of physiological and biochemical parameters of golden mullet will significantly increase the volume of reliable information about the physiological status of the organism of the studied species of mullet in the modern ecological conditions of the Caspian Sea.
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