Morphological, Biochemical And Genetic Variability Of Snakehead Species Based On Morphometric And Microsatellite Markers

Different morphological, biochemical and genetic studies were conducted in two channid species (Channa argus, Channa maculata) and their hybrid. For this purpose,25 different morphometric and meristic traits of Channa argus, Channa maculata and their hybrid were observed from 180 individuals. Data was analyzed by the analysis of variance (ANOVA) and multivariate analysis (Principal component analysis-PCA, Discriminant function analysis-DFA and Cluster analysis). Furthermore, the basic serum biochemical components and hematological indices of wild and cultured northern snakehead (Channa argus) have also been compared.In this report we have also described the development and characterization of microsatellite loci from the genome of the Channa argus. These microsatellite DNA markers have been further used to assess the genetic variation among six different populations of Channa argus.Following is the summary of the results:1. Different morphometric and meristic traits of the hybrid have been compared with its parents (Channa argus♂, Channa maculata♀) for efficient differentiation of these species. Regarding meristic traits, hybrids were having greatest number of anal fin rays (34.95±2.45) followed by northern snakehead C. argus (32.21±1.53) and blotched snakehead C. maculata (27.31±4.18), while number of pectoral and caudal fin rays of hybrids were existing between two parent species. Dorsal fin rays, scale above lateral line and scale below lateral line of hybrid were significantly similar to C. argus. Among 17 morphometric traits, only two traits (pre orbital length and eye diameter) distinguished hybrid from their parents while the external body shape of hybrid resembled more with C. argus than C. maculata. Principal components analysis revealed that the first three principal components (PC) for morphometric and meristic traits accounted for 83.09% of the total variance (50.27% for PCⅠ,23.91% for PCⅡand 8.91% for PCⅢ). Two PCs (ⅠandⅡ) explained 74.18% of the total variability. Cluster analysis revealed that C. maculata population was present in one group while C. argus and hybrid were clustered together in another group. The results of multivariate method (stepwise DFA) for morphological measurements and meristic counts revealed that the number of pectoral fin rays and anal fin rays entered in the analysis first. Both meristic and morphometric traits provided valuable information but meristic traits proved to be more useful than morphometric traits in differentiating these two closely similar fish species and their hybrid.2. Different haematological and serum biochemical parameters between cultured and wild specimens of the northern snakehead, Channa argus, in order to establish baseline values. Thirty sexually immature and disease free individuals of wild fish (37.70±13.68 cm total length,555.3±449.0 g weight) and cultured fish (36.82±1.72 cm total length,450.5±58.8 g weight) were examined. In cultured northern snakehead, the average values of alanine aminotransferases (370.1 IU 1-1), aspartate amino transferases (1145.3 IU 1-1), albumin (15.84 g 1-1), direct billuribin (6.15μmol 1-1), urea (1.40 mmol 1-1), glucose (21.54 mmol 1-) and cholesterol level (6.60 mmol 1-1) were significantly higher (P<0.05) than the wild fish. In specimens of the wild population, the corresponding values were 9.81 IU 1-1,394.1U 1-1,12.90 g 1-1,2.57μmol 1-1,0.97 mmol 1-1,2.36 mmol 1-1 and 4.38 mmol 1-1, respectively. No significant difference (P>0.05) was found for total protein, globulin, total bilirubin, chromium, sodium, chloride and triglyceride levels between wild and cultured populations. The mean values of red blood cells (RBCs) count, hematocrit, haemoglobin, and maen corpuscular volume (MCV) were significantly higher (P<0.05) in the cultured population, while the values of white blood cells (WBCs) count, erythrocyte sedimentation rate (ESR), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC) were significantly higher (P<0.05) in wild population. The study showed that the status of the fish is significantly impacted by the environmental conditions. Under culture, it is suggested that these physiological parameters can conveniently be employed as health monitoring tool in fish culture practices.3. A total of ten noval dinucleotide microsatellite loci were developed using genomic DNA enrichment protocol and characterized for one Channa argus population. Polymorphism was explored using 40 individuals from one natural population. The observed number of alleles ranged from 6-17. The ranges of observed and expected heterozygosity were 0.8000 to 1.0000 and 0.7269 to 0.9551 respectively, and the average of polymorphic information content (PIC) was 0.830. Significant deviations from Hardy-Weinberg equilibrium were detected only at one loci and linkage disequilibrium between three loci was found to be significant after applying Bonferroni correction (P<0.05). These newly developed markers should be significant in population genetic assessment studies or construction of genetic linkage map for this important snakehead fish species in future.4. Genetic diversity of wild northern snakehead (C. argus) population was analysed using microsatellite markers and compared to that of with hatchery northern snakehead population to determine the genetic impact of hatchery snakehead on wild snakehead population. Five wild populations and one hatchery population were analyzed using ten microsatellite markers. Microsatellite loci screened in this study showed high polymorphism in both hatchery and wild populations, as observed in an averaged number of allele per locus (4.5-6.1) and averaged expected heterozygosity (0.7806-0.7080). No significant difference in average allelic richness or expected heterozygosity was observed between hatchery and wild populations. AMOVA analysis indicated majority of the variance lies within individuals (93.59%) than among the populations (22.91%). According to neighbor joining-tree constructed on the basis of the genetic distance, the six populations fell into three groups showing no clear division between hatchery and wild populations. The information obtained in this study is useful for designing suitable management guideline and sustainable conservation for the northern snakehead in China.