Molecular Identification of Commercial Fish Maws using mtDNA 16S rRNA Nucleotide Sequences

Abstract

Background: Fish maws (dried swim bladders of fish) have long been used as a medicinal material and valuable tonic food which are very popular in Southeast Asia. It is difficult to identify the original species of fish maws sold on the market due to a lack of taxonomic characteristics. The present study aims to investigate the origin of commercial fish maws using DNA sequencing based on a partial sequence of the mtDNA 16S rRNA gene.Methods: Mitochondrial genomic DNA was extracted from a total of 44 individual fish maw samples collected from different markets by a QIAamp® DNA Mini Kit. The fragments of the 16S rRNA gene were amplified by PCR and bidirectionally sequenced using an ABI 3730 genetic analyser. Sequence assembly was performed with DNASTAR SeqMan software, and the resulting sequence was compared with reference sequences in GenBank using BLAST. Interspecific divergence and intraspecific variation were calculated by the Kimura 2-parameter model. Sample sequences were clustered in MEGA 6 using a neighbour-joining tree.Results: Forty-two of 44 fish maw samples were sequenced successfully. Fourteen taxa matched known fish species in the DNA sequence database, and 10 of them were supported by high homogeneity (99-100%). According to the results, 88% of the total samples belonged to family Sciaenidae. The clustering and genetic distance results, including in-group divergence and out-group divergence, indicated confidence in species identifications. Moreover, there was no strict correspondence between the commercial names provided by traders and the origin of the fish maws. This study also found a probable correlation between the molecular characteristics and morphological features of fish maws from croakers and non-croakers.Conclusion: In this study, DNA sequencing based on mtDNA 16S rRNA was carried out successfully to identify the origin of ~95% of the samples. This result indicated that 16S rRNA is a suitable barcode for identifying fish maws. The identification results allowed us to learn more about the fish species available in the fish maw market in Guangdong-Hongkong-Macao Great Bay. In addition, the association between trade category and species found in this study provides both consumers and merchants with an important reference for identifying the origin of fish maws.