Assessment of radioactivity level and associated radiological hazard in riverbed samples within industrial areas.

Terrestrial gamma radiation is one of the major outdoor radiation exposures to the general public that varies substantially based on the type and geological properties of the soil. The objective of this study is to evaluate the naturally occurring radioactive materials (NORMs) distribution and assess the hazard parameters in the riverbank soil within various industrial zones in the densely populated Dhaka and Chattogram cities of Bangladesh. The mean activities of 226Ra (37 ± 3), 232Th (58 ± 4), and 40K (1129 ± 18) Bqkg-1 in the assessed soil samples were found to be slightly higher than the world average values 32, 35, and 420 Bqkg-1, respectively. The mean radium equivalent activity (207.49 Bqkg-1) and the external and internal hazard indices were within the recommended limits of 370 Bqkg-1 and <1, respectively. The mean absorbed dose rate (99.47 nGyhr-1), annual effective dose (0.12 mSva-1), ELCR (4.27 × 10-4), and gamma level index (1.58) exceeded the world average values 59 nGyhr-1, 0.07 mSva-1, 2.9 × 10-4, and 1 respectively. However, the studied areas are safe from a radiological viewpoint with no radiation health hazard to the people. The results of this study can be utilized to produce factual baseline data for future studies.

Assessment of human health hazard associated with heavy metal accumulation in popular freshwater, coastal and marine fishes from south-west region, Bangladesh.

An analysis was conducted on both freshwater, coastal and marine fish species to evaluate the concentrations of heavy metals, with the aim of assessing their levels and examining the potential health risks for humans linked to the consumption of contaminated fish. This study estimate concentrations of Cr, Fe, Cu, As, Cd and Pb in 60 individuals belonging to 20 species (10 species for freshwater and another 10 for coastal and marine fishes) by using Atomic Absorption Spectrophotometer. Metal concentrations of Cr, Fe, and Pb in freshwater fishes and Cr, Fe, As, and Pb in marine fishes were exceeded the maximum allowable concentration (MAC). The Estimated Daily Intake (EDI), Average Pollution Load Index (APLI), Target Hazard Quotient (THQ), Hazard Index (HI) and Target Cancer Risk (TCR) of heavy metals were determined for the assessment of human health risk. Ranking order of the values of EDI for freshwater fishes, coastal and marine fishes were Cd > Fe > Pb > Cr > Cu > As and Cd > Fe > Pb > Cr > As > Cu. Highest APLI value of 8.14 (Puntius ticto) that is seriously polluted and 3.003 observed in Otolichthoides pama in freshwater and marine fishes, respectively. THQPb and THQAs for all the fish species were exceed the safe limit (THQ>1) suggesting potential health risk to consumers. The hazard index for both the fish samples were exceeded the USEPA (United States Environmental Protection Agency) permitted risk level (HI > 1). The target carcinogenic risk value for Cr and As were crossed the USEPA standard limit (TCR> 1E-04), which denotes that continuous consumption of studied fishes may cause health risk to the consumers. On the other hand, sensitivity analysis of freshwater, coastal and marine fishes indicates that all the metal concentrations were responsible factor for health risk.

RNAi-Based Therapy: Combating Shrimp Viral Diseases.

Shrimp aquaculture has become a vital industry, meeting the growing global demand for seafood. Shrimp viral diseases have posed significant challenges to the aquaculture industry, causing major economic losses worldwide. Conventional treatment methods have proven to be ineffective in controlling these diseases. However, recent advances in RNA interference (RNAi) technology have opened new possibilities for combating shrimp viral diseases. This cutting-edge technology uses cellular machinery to silence specific viral genes, preventing viral replication and spread. Numerous studies have shown the effectiveness of RNAi-based therapies in various model organisms, paving the way for their use in shrimp health. By precisely targeting viral pathogens, RNAi has the potential to provide a sustainable and environmentally friendly solution to combat viral diseases in shrimp aquaculture. This review paper provides an overview of RNAi-based therapy and its potential as a game-changer for shrimp viral diseases. We discuss the principles of RNAi, its application in combating viral infections, and the current progress made in RNAi-based therapy for shrimp viral diseases. We also address the challenges and prospects of this innovative approach.

Inter- and intra-specific genetic divergence of Asian tiger frogs (genus Hoplobatrachus), with special reference to the population structure of H. tigerinus in Bangladesh.

The five frog species of the genus Hoplobatrachus are widely distributed in Asia and Africa, with Asia being considered the genus' origin. However, the evolutionary relationships of Asian Hoplobatrachus species remain ambiguous. Additionally, genetic diversity and fundamental differentiation processes within species have not been studied. We conducted molecular phylogenetic analysis on Asian Hoplobatrachus frogs and population genetic analysis on H. tigerinus in Bangladesh using the mitochondrial CYTB gene and 21 microsatellite markers. The resultant phylogenetic tree revealed monophyly in each species, notwithstanding the involvement of cryptic species in H. chinensis and H. tigerinus, which are evident from the higher genetic divergence between populations. Bayesian inference of population structure revealed genetic divergence between western and eastern H. tigerinus populations in Bangladesh, suggesting restricted gene flow caused by barriers posed by major rivers. However, genetic distances among populations were generally low. A discrete population is located in the low riverine delta region, which likely reflects long-distance dispersal. These results strongly suggest that the environment specific to this river system has maintained the population structure of H. tigerinus in this region.

Development and characterization of 27 new microsatellite markers for the Indian bullfrog Hoplobatrachus tigerinus and its congeneric species.

The Indian bullfrog Hoplobatrachus tigerinus and its four congeneric species are common frog species and distributed throughout South Asia. Due to recent human activity, they are facing a changing environment and reduction in natural population size. For effective conservation and molecular ecological studies, we therefore isolated and characterized microsatellite loci for these frogs. We obtained genomic data using an Ion Torrent PGM sequencer and designed 54 primer sets for candidate loci. By screening for polymorphic loci in individuals of H. tigerinus and its congeneric species, we isolated 27 loci as highly polymorphic microsatellite loci. Eight of these loci were commonly applicable for all species except H. chinensis. Within two populations of H. tigerinus, the total number of alleles per locus and expected heterozygosity ranged from 2 to 18 and 0.271 to 0.938, respectively. No significant linkage disequilibrium was observed across all loci, and five showed a significant deviation from Hardy-Weinberg equilibrium in some populations after Bonferroni correction. Consequently, our findings suggest that these novel markers will be applicable for conservation genetic studies across varying scales from inter-population to inter-individual.

Postmating isolation in six species of three genera (Hoplobatrachus, Euphlyctis and Fejervarya) from family Dicroglossidae (anura), with special reference to spontaneous production of allotriploids.

In light of reproductive isolation being a fundamental aspect of the biological species concept, we performed crossing experiments using six species from three genera (Hoplobatrachus, Euphlyctis and Fejervarya) of family Dicroglossidae to explore postmating isolation in dicroglossid frogs. Our results revealed gametic isolation among these genera, although the intergeneric hybrids between female E. cyanophlyctis and male H. chinensis were not viable at the tadpole stage, while the hybrids between female E. cyanophlyctis and male H. tigerinus were inviable at the hatching stage. These results showed complete hybrid inviability between the two genera. Almost all interspecific hybrids between female H. tigerinus and male H. chinensis died of underdevelopment at the tadpole stage, whereas several hybrids developed normally and survived to maturity. Chromosomal observations and mtDNA and allozyme analyses confirmed that these mature hybrids were allotriploid, with two maternal genomes and one paternal genome. The present results suggest that the allotriploids were produced spontaneously, and histological observations confirmed their sex as sterile males. We also investigated the molecular relationships between H. tigerinus, H. chinensis, and the interspecific allotriploids by mitochondrial Cytb, 12S and 16S rRNA gene analyses. The maternal inheritance mode of mitochondrial genomes was retained in the hybrids. Finally, the present results suggest that the degree of postmating isolation reflects phylogenetic relationship. In addition, we speculate that allotriploids may be produced via hybridization among cryptic species.

Cryptic anuran biodiversity in Bangladesh revealed by mitochondrial 16S rRNA gene sequences.

To survey the diversity of anuran species in Bangladesh, we compared mitochondrial 16S rRNA gene sequences (approximately 1.4 kbp) from 107 Bangladesh frog specimens. The results of genetic divergence and phylogenetic analyses incorporating data from related species revealed the occurrence of at least eight cryptic species. Hoplobatrachus tigerinus from two districts diverged considerably, indicating the involvement of a cryptic species. Two Fejervarya sp. (large and medium types) and Hylarana cf. taipehensis formed lineages distinct from related species and are probably new species. Microhyla cf. ornata differed from M. ornata with respect to type locality area and involved two distinct species. In addition, we found that Hylarana sp. and Microhyla sp. did not match congeners examined to date in either morphology or 16S rRNA sequence. The occurrence of M. fissipes was tentatively suggested. Consequently, at least, 19 species were found from Bangladesh in this study. These findings revealed a rich anuran biodiversity in Bangladesh, which is unexpected considering the rather simple topographic features of the country.

Complete mitochondrial genomes and novel gene rearrangements in two dicroglossid frogs, Hoplobatrachus tigerinus and Euphlyctis hexadactylus, from Bangladesh.

We determined the complete nucleotide sequences of mitochondrial (mt) genomes from two dicroglossid frogs, Hoplobatrachus tigerinus (Indian Bullfrog) and Euphlyctis hexadactylus (Indian Green frog). The genome sizes are 20462 bp in H. tigerinus and 20280 bp in E. hexadactylus. Although both genomes encode the typical 37 mt genes, the following unique features are observed: 1) the ND5 genes are duplicated in H. tigerinus that have completely identical sequences, whereas duplicated ND5 genes in E. hexadactylus possessed dissimilar substitutions; 2) duplicated control region (CR) in H. tigerinus has almost identical sequences whereas single control region (CR) was found in E. hexadactylus; 3) the tRNA-Leu (CUN) gene is translocated from the LTPF tRNA cluster to downstream of ND5-1 in H. tigerinus, and the tRNA-Pro gene is translocated from the LTPF tRNA cluster to downstream of CR in E. hexadactylus; 4) pseudo tRNA-Leu (CUN) and tRNA-Pro genes are observed in E. hexadactylus; and 5) two tRNA-Met genes are encoded in both species, as observed in the previously reported dicroglossid mt genomes. Almost all observed gene rearrangements in H. tigerinus and E. hexadactylus can be explained by the tandem duplication and random loss model, except translocation of tRNA-Pro in E. hexadactylus. The novel mt genomic features found in this study may be useful for future phylogenetic studies in the dicroglossid taxa. However, the mt genome with interesting features found in the present study reveal a high level of variation of gene order and gene content, inspiring more research to understand the mechanisms behind gene and genome evolution in the dicroglossid and as well as in the amphibian taxa in future studies.

Genetic divergence and evolutionary relationships in six species of genera Hoplobatrachus and Euphlyctis (Amphibia: Anura) from Bangladesh and other Asian countries revealed by mitochondrial gene sequences.

To elucidate the species composition, genetic divergence, evolutionary relationships, and divergence time of Hoplobatrachus and Euphlyctis frogs (subfamily Dicroglossinae, family Ranidae) in Bangladesh and other Asian countries, we analyzed the mitochondrial Cyt b, 12S, and 16S rRNA genes of 252 specimens. Our phylogenetic analyses showed 13 major clades corresponding to several cryptic species as well as to nominal species in the two genera. The results suggested monophyly of Asian Hoplobatrachus species, but the position of African Hoplobatrachus occipitalis was not clarified. Nucleotide divergence and phylogenetic data suggested the presence of allopatric cryptic species allied to Euphlyctis hexadactylus in Sundarban, Bangladesh and several parapatric cryptic species in the Western Ghats, India. The presence of at least two allopatric cryptic species among diverged Euphlyctis cyanophlyctis in Bangladesh, India, and Sri Lanka was also suggested. In some cases, our estimated divergence times matched the paleogeological events of South and Southeast Asian regions that may have led to the divergence of Hoplobatrachus and Euphlyctis taxa. Especially, land formation at Bangladesh (15-10Ma) may have allowed the spread of these frog taxa to Southeast Asian areas, and the aridification of central India (5.1-1.6Ma) might have affected the gene flow of widely distributed species. The present study revealed prior underestimation of the richness of the amphibian fauna in this region, indicating the possible occurrence of many cryptic species among these groups.

Genetic differentiation of the Fejervarya limnocharis complex from Bangladesh and other Asian countries elucidated by allozyme analyses.

The present study was conducted to elucidate the genetic divergence and the phylogenetic relationships in the F. limnocharis complex from Bangladesh and other Asian countries such as Sri Lanka, Thailand, Malaysia, Taiwan and Japan by allozyme analyses. We used a total of 95 frogs of the F. limnocharis complex from these countries and F. cancrivora from the Philippines as an outgroup. Based on body size, the F. limnocharis complex from Bangladesh was divided into three distinct groups: large, medium and small types. Allozyme analyses were carried out with 28 loci encoding 20 enzymes and two blood proteins by horizontal starch-gel electrophoresis. When genetic distance was calculated, distinct divergence was found among the three types: mean genetic distance was 0.782 between the small and medium types, 1.458 between the large and medium types, and 1.520 between the large and small types. Phylogenetic trees based on genetic distance showed that all populations of Bangladesh small type strongly formed a cluster and were found to be most closely related to the Sri Lanka population; that all populations of Bangladesh large type formed a very strong cluster and were grouped with several populations from Thailand, Malaysia, Japan, and Taiwan; and that the medium type was segregated from all other groups. This may imply that each of the three types is a different species, and that the medium type is possibly an undescribed taxon.

Genetic divergence and reproductive isolation in the genus Fejervarya (Amphibia: Anura) from Bangladesh inferred from morphological observations, crossing experiments, and molecular analyses.

In the present study, morphological examinations, crossing experiments and molecular analyses were performed to elucidate the degree of genetic divergence and phylogenetic relationships within the genus Fejervarya from Bangladesh and other Asian countries. Morphological characteristics revealed that Fejervarya species from Bangladesh were divided into four distinct groups: large, medium, small, and mangrove types. Crossing experiments indicated the involvement of three reproductive isolating mechanisms: gametic isolation between the large type and mangrove type, hybrid inviability between the large type and two other types, and hybrid sterility between the medium and small types. Experimental results also indicated that these four types of frogs merit the status of individual species of Fejervarya . Molecular analyses based on mtDNA gene sequences showed that the Bangladesh Fejervarya species were largely divided into three groups: the mangrove type, large type, and others, with the last further subdivided into the medium and small types. Comparison with other Asian Fejervarya species revealed that the Bangladesh mangrove type (which resembled F. cancrivora in morphology) was closely related to F. cancrivora from India, Thailand, and the Philippines; the large type belonged to the F. iskandari group and closely resembled F. orissaensis ; the small type was included in the South Asian or Indian group, and was closest to F. syhadrensis from India and Sri Lanka, whereas the medium type was most closely related to F. limnocharis from Myanmar among all described species of this genus.

Genetic relationships and reproductive-isolation mechanisms among the Fejervarya limnocharis complex from Indonesia (Java) and other Asian countries.

In order to elucidate the genetic relationships and reproductive-isolation mechanisms among the Fejervarya limnocharis complex from Indonesia and other Asian countries, allozyme analyses and crossing experiments were carried out using 208 individuals from 21 localities in eight Asian countries. The allozyme analyses revealed that 17 enzymes examined were controlled by genes at 27 loci, and that 7.9 phenotypes were produced by 5.2 alleles on average. The two species recognized in F. limnocharis sensu lato from Southeast Asia (i.e., F. limnocharis sensu stricto and F. iskandari) were found to occur sympatrically at three localities (Bogor, Cianjur and Malingping), all on Java, Indonesia. Fejervaya iskandari was dominant at each of these localities and showed substantial geographic genetic variation. Laboratory-produced hybrids between F. limnocharis and F. iskandari from Java became underdeveloped and died at the tadpole stage, suggesting that these species are completely isolated by hybrid inviability. Hybrids between topotypic F. limnocharis and the Malaysian and Japanese conspecific populations developed normally to metamorphosis. Likewise, hybrids between topotypic F. iskandari and the Thailand and Bangladesh conspecific populations also showed normal viability throughout larval development. The present allozyme analyses and crossing experiments strongly suggested the presence of two distinct forms, the large type and the small type, in the F. limnocharis complex from Asia, and further subdivision of the large type into the F. limnocharis assemblage and the F. iskandari assemblage. The small type was found in samples from India, Thailand, Bangladesh and Sri Lanka, and included at least three different species. The sample from Pilok, Thailand, was considered to represent an undescribed species.