No abstract

Tenualosa ilisha is a popular anadromous and significant trans-boundary fish. For sustainable management and conservation of this fish, drawing an appropriate picture reflecting population status of this species is very essential based on their all-strategic habitats in Bangladesh. In this study, 139 samples from 18 sites were collected and cross-species gene enrichment method was applied. Like most of the Clupeiforms, nucleotide diversity of this shad was very low (0.001245–0.006612). Population differences between most of the locations were low and not significant (P > 0.05). However, P values of a few locations were significant (P < 0.05) but their pairwise FST values were very poor (0.0042–0.0993), which is inadequate to recognize any local populations. Our study revealed that the presence of a single population in the Bangladesh waters with some admixtured individuals, which may contain partial genes from other populations. Most of the individuals were admixed without showing any precise grouping in the ML IQtree and Network, which might due to their highly migratory nature. Fishes from haors and small coastal rivers were not unique and no genetic differences between migratory cohorts. The hilsa shad fishery should be managed considering it as a single panmictic population in Bangladesh with low genetic diversity.

Among marine species distributed in the Indian Ocean and the Pacific, the Indo–Pacific Barrier (IPB) has been found to be an important barrier of divergence of species distributed on both sides. Among the five species of the genus Pampus, only Pampus chinensis and P. cinereus are distributed across the western Pacific and the Indian Oceans and have not been studied comparatively using extensive sampling and gene markers. Furthermore, the origin and history of genus Pampus remain unrevealed. We used thousands of nuclear loci based on target gene enrichment to explore genetic structure of P. chinensis and P. cinereus across the western Pacific and Indian Oceans. We performed divergence dating and ancestral area reconstruction analysis and inferred the dispersal routes of the Pampus species. The results suggest that the IPB played an important role in the differentiation between populations among the two oceans for both P. chinensis and P. cinereus, dividing species into the Pacific lineage and the Indian Ocean lineage. Low sea level in the late Pleistocene may be the main cause. The result also showed that the South China Sea was the center of origin of the genus Pampus, and dispersal routes of each species may be associated with the ocean currents. Our study provided new examples for the IPB effect on marine species.

Telomeres, at the ends of chromosomes, protect chromosomes from fusion and preserve genomic stability. However, the molecular mechanisms underlying telomere attrition-induced genome instability remain to be understood. We systematically analyzed the expression of retrotransposons and performed genomic sequencing of different cell and tissue types with telomeres of varying lengths due to telomerase deficiency. We found that critically short telomeres altered retrotransposon activity to promote genomic instability in mouse embryonic stem cells, as evidenced by elevated numbers of single nucleotide variants, indels and copy number variations (CNVs). Transpositions of retrotransposons such as LINE1 resulting from the short telomeres can also be found in these genomes with elevated number of mutations and CNVs. Retrotransposon activation is linked to increased chromatin accessibility, and reduced heterochromatin abundance correlates with short telomeres. Re-elongation of telomeres upon recovery of telomerase partly represses retrotransposons and heterochromatin accumulation. Together, our findings suggest a potential mechanism by which telomeres maintain genomic stability by suppressing chromatin accessibility and retrotransposon activity.

Tenualosa ilisha is a popular anadromous and significant trans-boundary fish. For sustainable management and conservation of this fish, drawing an appropriate picture reflecting population status of this species is very essential based on their all-strategic habitats in Bangladesh. In this study, 139 samples from 18 sites were collected and cross-species gene enrichment method was applied to discover the exact population status of the fish. Like most of the Clupeiforms, nucleotide diversity and variation of this shad were very low. Population differences between most of the locations were low and not significant. However, P values of a few locations were significant (P< 0.05) but their pairwise FST values were very poor, which is inadequate to recognize any local populations. Structure analysis, PCA and maximum likelihood IQtree all indicated the presence of a single population in the Bangladesh water with some admixture individuals, which may contain partial genes from other populations. In the ML IQtree and Network, most of the individuals were mixed without showing any precise grouping, which might due to their highly migratory nature. Fishes from special type of habitats, e.g., haors, small coastal rivers etc. were not unique and no genetic differences between migratory cohorts were found.