Abstract
The present study aims to apply a DNA barcoding tool through amplifying two mitochondrial candidate genes i.e., COI and 16S rRNA for accurate identification of fish, aquatic molluscs and crustaceans of Sundarbans mangrove wetland, to build a reference library of fish and shellfishes of this unique ecosystems. A total of 185 mitochondrial COI barcode sequences and 59 partial sequences of the 16S rRNA gene were obtained from 120 genera, 65 families and 21 orders of fish, crustaceans and molluscs. The collected samples were first identified by examining morphometric characteristics and then assessed by DNA barcoding. The COI and 16S rRNA sequences of fishes and crustaceans were clearly discriminated among genera in their phylogenies. The average Kimura two-parameter (K2P) distances of COI barcode sequences within species, genera, and families of fishes are 1.57±0.06%, 15.16±0.23%, and 17.79±0.02%, respectively, and for 16S rRNA sequences, these values are 1.74±.8%, 0.97±.8%, and 4.29±1.3%, respectively. The minimum and maximum K2P distance based divergences in COI sequences of fishes are 0.19% and 36.27%, respectively. In crustaceans, the K2P distances within genera, families, and orders are 1.4±0.03%, 17.73±0.15%, and 22.81±0.02%, respectively and the minimum and maximum divergences are 0.2% and 33.93%, respectively. Additionally, the present study resolves the misidentification of the mud crab species of the Sundarbans as Scylla olivacea which was previously stated as Scylla serrata. In case of molluscs, values of interspecific divergence ranges from 17.43% to 66.3% in the barcoded species. The present study describes the development of a molecular and morphometric cross-referenced inventory of fish and shellfish of the Sundarbans. This inventory will be useful in future biodiversity studies and in forming future conservation plan.
Highlights
Mangroves are among some of the most productive and biologically diverse ecosystems on the planet, and create unique ecological environments for variety of plants, birds, reptiles, mammals and aquatic fauna
We obtained 203 sequences of 50 region of mtDNA c oxidase I (COI) and 16S rRNA gene that were derived from 113 fish species under 105 genera, 56 families and 15 orders
144 sequences of 93 species belonged to COI gene marker and 59 sequences of 43 species were comprised of 16S rRNA gene
Summary
Mangroves are among some of the most productive and biologically diverse ecosystems on the planet, and create unique ecological environments for variety of plants, birds, reptiles, mammals and aquatic fauna. These ecospheres provide vital and unique ecosystem goods and services to human society, and coastal and marine systems [1]. Mangroves are mainly found along tropical and sub-tropical coastal regions of the world [2] These intertidal wetland ecosystems support a complex aquatic food web [3]. The aquatic faunas of mangroves are uniquely adapted to survive under wide ranges of salinities They are well adapted with tidal amplitudes, temperatures and silty turbid water and hypoxic waterlogged conditions. Mangrove areas act as important breeding and nursery habitat for many species of fishes and invertebrates such as oysters, shrimp, and crab due to high density of organic matter deposition in a relatively small area [7]
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