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The present study was conducted to determine the effects of squid oil on the endangered butter catfish, Ompok pabda to confer enhanced breeding with embryonic and larval development for promoting its aquaculture. A total of 360 fish were obtained from the Brahmaputra River, Mymensingh, Bangladesh, of which, 60 fish stocked in each tank having an initial weight and length of 16.35 ± 0.57 g and 15.25 ± 0.38 cm, respectively, in the cisterns of 1.22 × 2.44 × 1.25 m (total 6 cisterns) maintained at 90 cm water depth. During the experimental period, a constant physico-chemical conditions of water such as temperature, pH, and dissolved oxygen (DO) were 26.5 ± 2 °C, 7.4 ± 0.2, and 6.7 ± 0.5 ppm, respectively, were maintained in each cistern. As the source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), dietary 1 % squid oil (SQO) was supplemented in the diet of the treated group (SQO diet) to compare while the control group offered with basal diet without SQO supplementation (CON diet). The fecundity, spawning, fertilization, hatching rate, and survival rate of fry in SQO group were significantly (P

Fish mycotic disease outbreaks occur due to infections with oomycete pathogens such as Saprolegnia spp. and Aphanomyces invadans, and cause large-scale fish production losses. Despite its negative impact on aquaculture, little is known about the diversity of oomycete pathogens. The aim of this study was to identify the diversity of pathogenic oomycetes causing infections in major aquaculture zones of Mymensingh and Jessore regions in Bangladesh. A total of 449 water and infected fish samples were collected from 28 fish farms in both regions of which 29 samples were able to grow out with mycelia on the Potato Dextrose Agar (PDA)/Glucose Peptone Yeast Agar (GPYA) plates. Sequence database searches using the rRNA Internal Transcribed Spacer (ITS) region revealed that 15 belonged to Pythium spp., 12 were Aphanomyces invadans and two corresponded to Saprolegnia parasitica. Five isolates of Pythium spp. were identified to the species level: one was closely related to Pythium catenulatum, four to Pythium rhizo-oryzae, rest were identified up to genus. The Pythium spp. were only isolated from water samples whereas A. invadans and S. parasitica were found in fish lesions. Phylogenetic analysis revealed that a single A. invadans clone exists in the sampled area. The results obtained confirm the existence of pathogenic oomycetes in Bangladesh fish farms and this will pave future research on diversity, prevention and control measures. Keywords: Oomycete, Saprolegnia, Aphanomyces invadans, Internal transcribed spacer (ITS), Phylogeny

Pollutant dispersion in urban areas has been a key concern in densely populated cities because pollutants can negatively impact human health and the environment. Topography and urban obstructions, such as buildings, greatly affect the atmospheric fluid flow, leading to the dispersion process. Street canyons are usually formed in highly populous cities due to the close proximity of buildings to streets to serve commercial purposes. It can also be termed as pollutant traps that exact adverse effects on urban life. Street canyons cause changes in pollutant dispersion, particularly in the case of vehicle exhaust air pollutants, which cannot be transported by the wind owing to the presence of buildings acting as impediments regardless of the wind flow. Hence, it is imperative to completely understand the behavior of pollutants within the confined urban surroundings for further improving the urban air quality. This study explores the effects of street canyons on the busiest street of Dhaka city in Bangladesh. The Reynolds-averaged Navier–Stokes based dispersion model is used to investigate the air quality phenomenon. Building height, width, building distance, and road width have been taken into consideration in the simulation. It is expected that the findings of the current study would be helpful for urban planners and designers of Dhaka city.

Genetic information is essential for conservation and future aquaculture development of the endangered catfish Rita rita (Hamilton, 1822). Two hundred catfish, R. rita, 50 from four rivers, the Old Brahmaputra, Jamuna, Meghna and Kangsa were collected and analysed to evaluate the genetic diversity and population structure using five microsatellite primers (Cba06-KUL, Cba08-KUL, Cba09-KUL, Phy03-KUL and Phy07-KUL). Four of the five amplified loci were found polymorphic (P95) in all the populations and 46 alleles were recorded with 9 to 14 alleles per locus. Differences were observed in the total number of alleles ranging from 41 to 44, effective number of alleles from 29.96 to 37.46, observed heterozygosity from 0.57 to 0.76, Shannon’s information index from 2.09 to 2.30 and polymorphic information content from 0.84 to 0.88 among the four populations. Results exposed the highest levels of genetic diversity in the Meghna population while the lowest in the Kangsa population of R. rita. All the populations were significantly deviated (P < 0.001) from the Hardy-Weinberg equilibrium for all the loci. Nei’s genetic distance between populations ranged 0.007 to 0.017 with low overall genetic difference FST = 0.011 and high gene flow Nm = 24.333, indicating that R. rita populations were not subdivided. This study revealed a high level of gene diversity with deficiency in genetic heterogeneity in all the populations of R. rita, emphasising natural management, conservation and rehabilitation measures of this species.

The common sea hare Aplysia kurodai is known to be a good source for the enzymes degrading seaweed polysaccharides. Recently four cellulases, i.e., 95 kDa, 66 kDa, 45 kDa and 21 kDa enzymes, were isolated from A. kurodai (Tsuji et al., PLoS ONE, 8, e65418, 2013). The former three cellulases were regarded as glycosyl-hydrolase-family 9 (GHF9) enzymes, while the 21 kDa cellulase was suggested to be a GHF45 enzyme. The 21 kDa cellulase was significantly heat stable, and appeared to be advantageous in performing heterogeneous expression and protein-engineering study. In the present study, we determined some enzymatic properties of the 21 kDa cellulase and cloned its cDNA to provide the basis for the protein engineering study of this cellulase. The purified 21 kDa enzyme, termed AkEG21 in the present study, hydrolyzed carboxymethyl cellulose with an optimal pH and temperature at 4.5 and 40oC, respectively. AkEG21 was considerably heat-stable, i.e., it was not inactivated by the incubation at 55oC for 30 min. AkEG21 degraded phosphoric-acid-swollen cellulose producing cellotriose and cellobiose as major end products but hardly degraded oligosaccharides smaller than tetrasaccharide. This indicated that AkEG21 is an endolytic -1,4-glucanase (EC 3.2.1.4). A cDNA of 1,013 bp encoding AkEG21 was amplified by PCR and the amino-acid sequence of 197 residues was deduced. The sequence comprised the initiation Met, the putative signal peptide of 16 residues for secretion and the catalytic domain of 180 residues, which lined from the N-terminus in this order. The sequence of the catalytic domain showed 47-62% amino-acid identities to those of GHF45 cellulases reported in other mollusks. Both the catalytic residues and the N-glycosylation residues known in other GHF45 cellulases were conserved in AkEG21. Phylogenetic analysis for the amino-acid sequences suggested the close relation between AkEG21 and fungal GHF45 cellulases.