Genetic Characteristics of Paddlefish (Polyodon Spathula (Walbaum, 1792)) Brood Stocks

Abstract

Goal. The studing of specificity of genetic variability by the loci of biochemical systems and cytogenetic indicators in groups of paddlefish caught at the ponds of the IF "Nyvka" of the Kyiv region and fish farm "Girskyi Tikich" of the Cherkasy region.
 Methods. The analysis of the distribution of alleles and genotypes frequencies in paddlefish (Polyodon spathula W.) was carried out according to the loci of albumin (ALB), malatedehydrogenase (MDH, K.F.1.1.1.37), malic enzyme (ME, K.F.1.1.1.40), esterase (EST, K.F. 3.1.1.1) and carbonic anhydrase (CA, K.F. 4.2.1.1.). For research were used methods of vertical polyacrylamide and horizontal starch electrophoresis with following histochemical staining and genotyping of alleles of investigated loci. The frequency of allelic and genotypic variants was calculated. The observed and expected levels of heterozygosity for each individual locus and the level of average heterozygosity were determined. It was calculated the Wright fixation index Fis. Statistical processing of experimental data was performed using the "Biosys-1" program.
 It was carried out cytogenetic analysis in peripheral blood smears of paddlefish using the micronucleus test and analysis of apoptosis frequency.There were counted the occurrence frequency of erythrocytes with micronuclei (EMN), lymphocytes with micronuclei (LMN), binuclear lymphocytes (BNL) and apoptosis. Statistical probability of differences by the cytogenetic indicators was assessed using the Student's t-distribution.
 Results. The analysis of variability of the genetic structure of paddlefish groups was carried out according to loci of biochemical systems of esterase, carbonic anhydrase, albumin, malatedehydrogenase, malic enzyme and cytogenetic indicators. The group of paddlefish from "Girsky Tikich" was differentiated by a significant advantage of the fast-migrating Ca F allele (0.717), compared to Ca S (0.283). The group of paddlefish from "Nyvka" was characterized by a high frequency of the Mdh F allele (0.724), compared to Mdh S (0.276). In both groups of paddlefish, the ALB locus stood out due to the significant predominance of the fast-migrating Alb A allele. It was observed the statistically significant excess of heterozygotes by the MDH locus (Р < 0.05) in the group from "Girsky Tikich" and by the EST and CA loci (Р < 0.05) in the group from "Nyvka". Other studied loci in both groups of paddlefish according to the distribution of observed and expected genotypes were balanced. The value of the fixation index showed a high level of genetic variability by the CA (FIS = -0.381) and EST (FIS = -0.476) loci, compared to those expected in the group from “Nyvka” and the MDH locus (FIS = -0.473) in the group of fish from “Girsky Tikicha".
 According to cytogenetic indicators, the studied group from the farm "Girsky Tikich" was characterized by an medium value of EMN (2.8 ± 0.4‰) but, at the same time, a low level of apoptosis (0.8 ± 0.5‰). Ass to results of the comparative analysis of the same age groups of paddlefish caught in the same period in the farms "Nyvka" of the Kyiv region. and "Girsky Tikich" of the Cherkasy region. it was established that both groups of paddlefish are characterized by a different, but not high level of cells with micronuclei.
 According to the frequency of apoptosis (1.2 ± 0.3‰) the groups of paddlefish from farm "Nyvka" was characterized by higher values. Statistically significant differences were determined by the frequency of EMN (Р < 0.005). However, the middle values of this indicator indicates about normal cellular homeostasis and favorable living conditions.
 Conclusions. In general, the level of variability of the genetic structure at the studied loci in both groups of paddlefish was similar. This is indicated by the established values of the average heterozygosity level in the group of paddlefish from "Nyvka" (Hо = 0.517 ± 0.093) and group from "Girsky Tikich" (Hо = 0.580 ± 0.051) and which did not significantly differ from the values of the expected level of average heterozygosity (Hе = 0.419 ± 0.060 and 0.455 ± 0.029, in both farms respectively). The average values of the inbreeding coefficient (Fis) in the group from "Nyvka" (23.5%) and the group from "Girsky Tikich" (29.2%) are indicated about absence of inbreeding in the studied herds. The analysis of genetic variability indicated the similarity and homogeneity of the genetic characteristics of both groups of paddlefish, which indicates about possible common origin of these groups of fish.
 The results of studies of paddlefish breeding herd from farms "Nyvka" and "Girsky Tikich" are demonstrated that these groups are characterized by low values of cytogenetic indicators, which indicates about stable state of their genetic apparatus.
 Comparative analysis of the same age groups of paddlefish from farms "Nyvka" and "Girsky Tikich" showed statistically significant differences by the frequency of EMN (Р < 0.005), and that the last group was characterized a higher value of EMN (2.8 ± 0.4‰). Thus, the analysis of biochemical loci indicates about the similarity and homogeneity of the genetic characteristics of both groups of paddlefish, which may indicates about the common origin of these fish groups.
 Also, as a result of cytogenetic studies, it was established that for an objective assessment of the heterogeneity of paddlefish breeding herds, it is necessary to analyze cytogenetic indicators in cells of both the erythrocyte and leukocyte series.