Genetic Diversity, Phylogenetic Relationship and Status of Shrimps (Crustacea:Decapoda) of Bangladesh

Abstract

Shrimp, a popular and delicious food item worldwide, holds significant commercial and food value, providing a vital source of protein and contributing to a multi-billion-dollar industry in both wild-caught and farmed varieties. Belonging to the order Decapoda, shrimp play a vital role in both marine and freshwater ecosystems. However, a comprehensive, systematic taxonomic study, especially in molecular taxonomy, has not been conducted for these species in Bangladesh. To address this gap, the present study aimed to explore the genetic diversity, phylogenetic relationships, and status of shrimp species found in Bangladesh. An integrative taxonomic approach was used, combining morphological examination, DNA barcoding, and molecular species delimitation to provide a broad understanding of the systematics of shrimps in the region. Specimens were initially identified morphologically, followed by molecular analysis using two genetic markers: the mitochondrial cytochrome c oxidase I (COI) gene and the 16S ribosomal RNA (16S rRNA) gene. 50 shrimp species, representing six families and 16 genera, were morphologically identified, and 38 species and two genera were further confirmed through molecular analysis. A total of 127 sequences were generated, comprising of 55 COI and 72 16S rRNA sequences. Sequence analysis revealed 136 conserved, 561 variable, and 321 parsimony-informative sites for the COI gene, and 101 conserved, 583 variable, and 372 parsimony-informative sites for the 16S rRNA gene. The average GC content was 40.87% for COI and 33.49% for 16S rRNA. Genetic divergence was assessed with mean distances of 1.18 ± 0.02%, 23.53 ± 0.08%, and 28.29 ± 0.05% within species, genus, and family for the COI gene. For the 16S rRNA gene, the corresponding values were 2.94 ± 0.09%, 13.91 ± 0.06%, and 25.26 ± 0.04%. Notably, the mean interspecific genetic distance for COI was 34 times greater than the intraspecific distance, while for 16S rRNA, it was 15 times greater, with barcode gaps of 38.54% and 40.91% for the two markers, respectively. Phylogenetic trees based on the Neighbor-Joining (NJ) method were generated for each gene marker to explore the phylogenetic relationships among the identified species. Additionally, 11 species were newly recorded from Bangladesh, marking their first geographic occurrence in the region. This is the first comprehensive study combining morpho-taxonomy, molecular analysis, and phylogenetic relationships of shrimps from Bangladesh. The study underscores the need for effective conservation strategies and sustainable management practices to preserve the rich shrimp diversity in Bangladesh, as revealed by the molecular and phylogenetic findings. The results not only enhance our understanding of shrimp biodiversity in Bangladesh but also lay a foundation for future research on the ecological and evolutionary dynamics of these crucial aquatic organisms.