Genetic divergence and molecular phylogenetics of Puntius spp. based on the mitochondrial cytochrome b gene

Invasion of African Clarias gariepinus Drives Genetic Erosion of the Indigenous C. batrachus in Bangladesh

Simple Summary

Bangladesh has substantially increased aquaculture production over the last few decades, and the exotic species share a significant portion of the total fish production. Although exotic species are contributing to aquaculture production, a few of them are causing biodiversity loss and genetic erosion of native species. The African catfish Clarias gariepinus is a highly carnivorous species and predates small indigenous freshwater fishes when escaping into natural water bodies. In addition, the hybridization of C. batrachus and C. gariepinus is considered a threat to the indigenous population. Although the government of Bangladesh has banned the farming of C. gariepinus, this species has been identified in local markets, and evidence of hybridization between C. gariepinus and C. batrachus has been found. This study revealed genetic erosion of native C. batrachus by the gene sequences of cytochrome c oxidase subunit I and cytochrome b. The phylogenetic tree confirmed the occurrences of hybridization between C. gariepinus and C. batrachus. Genetic erosion in the native catfish population is alarming for aquaculture sustainability and biodiversity conservation in Bangladesh.

Abstract

The African catfish Clarias gariepinus has been introduced for aquaculture in Bangladesh due to the scarcity of indigenous C. batrachus fingerlings. However, the government of Bangladesh has banned the farming of C. gariepinus due to the carnivorous nature of this species. Recently C. gariepinus has been reported by fish farmers and consumers in Bangladesh, and unplanned hybridization between native and exotic species has been suspected. This study attempts to know the purity of C. batrachus by analyzing mitochondrial genes. Both directly sequenced and retrieved Cytochrome C Oxidase subunit I (COI) and cytochrome b (Cytb) genes from C. gareipinus and C. batrachus were analyzed by MEGA software. The morphologically dissimilar C. batrachus showed the least genetic distance (0.295) from C. gariepinus, which provided evidence of hybridization between the two species. Maximum likelihood (ML) phylogenetic trees showed that C. batrachus from Bangladesh did not cluster with C. batrachus of other countries, instead C. batrachus clustered with the exotic C. gariepinus. The suspected hybrid formed sister taxa with the exotic C. gariepinus. The study corroborates the genetic deterioration of C. batrachus by unplanned hybridization with the invasive C. gariepinus. Unplanned hybridization has deleterious consequences; therefore, immediate action is necessary for aquaculture sustainability and biodiversity conservation in Bangladesh.

Molecular-genetic diversity of the endangered Dalmatian barbelgudgeon, Aulopyge huegelii from the Buško Blato reservoir

A number of studies investigating different aspects of IUCN endangered species, Aulopyge huegelii Heckel, 1843 (Dalmatian barbelgudgeon) biology have been conducted, but data on molecular genetics are lacking. The goal of this survey was to assess the genetic structure of the A. huegelii population from the Buško Blato reservoir, based on four mitochondrial DNA regions and five microsatellite loci. Excluding cytochrome b, more than one haplotype has been detected in all sequenced mtDNA regions, most of which had not been previously described. A total of seven composite haplotypes were detected. Nucleotide diversity was relatively low for all coding genes but slightly higher for the control region. Microsatellite analysis revealed a relatively high value of major allele frequency, lower values of observed and expected heterozygosity, as well as a moderately reduced number of alleles and genotypes in three of the five observed loci. Although with a clear trend of decline, the level of genetic diversity is still sufficient to ensure the subsistence of the population if the stressors are removed. Otherwise, the loss of heterozygosity will continue, possibly to the point of a complete eradication of the Dalmatian barbelgudgeon from the Buško Blato reservoir.

Taxonomic validation of five fish species of subfamily Barbinae from the Ganga river system of northern India using traditional and truss analyses

Morphometric differences were investigated among five fish species of subfamily Barbinae from the Ganga river system through traditional morphometrics and the truss network system. Species taken into account were Puntius chola (Hamilton 1822), Puntius sophore (Hamilton 1822), Pethia ticto (Hamilton 1822), Pethia conchonius (Hamilton 1822) and Systomus sarana (Hamilton 1822). Although, taxonomists carefully examine external body features to discriminate these species, there is still a risk of misidentification during a visual assessment. In the present study, the traditional morphological analysis included 22 morphometric measurements and 10 meristic counts. Truss network system of 14 landmarks was interconnected to yield 91 distance variables. The principal component analysis (PCA), discriminant function analysis (DFA) and cluster analysis (CA) were employed in order to determine morphometric variations. In traditional analysis, 29 characters out of 32 were found significant (p<0.05). Eight principal components were extracted through PCA explaining 85.30% of the total variance in samples, DFA correctly classified 100.0% of original grouped cases and 100.0% of cross-validated grouped cases. Truss analysis showed that all the 90 characters were significant (p<0.05). PCA extracted four principal components explaining 96.45% of the total variance. DFA correctly classified 96.1% of original grouped cases and 92.1% of cross-validated grouped cases. The results acquired from the traditional as well as truss analyses indicate significant morphometric heterogeneity. However, variations are not the same for the two different methods (traditional and truss) employed for the analyses. Shape differences among species were evident from relative warps (RW) supporting truss network analysis. Geometric morphometric methods (GMM), but limited use of Procrustes methods revealed even very small dissimilarity between groups. In spite of determining the morphometric differentiation among species, the present study also provides a useful insight on the application and complementary role of truss analysis with traditional morphometric analysis in the correct classification of the selected species.

Complete mitochondrial genome of rosy barb, Puntius conchonius

In this study, we sequenced and determined the complete mitochondrial genome of rosy barb (Puntius conchonius). The circular mitochondrial genome (17,082 bp) consisted of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 1 control region. This is the first report on the complete mitogenome sequence of rosy barb (P. conchonius).