Antibiotic use in tertiary care hospitals in Bangladesh: Revealing the extent through a point prevalence survey.

BACKGROUND: Prevalent use of antibiotics in hospitals results in antimicrobial resistance (AMR), rising mortality, and substantial financial burden. This study assessed the current pattern of antibiotic use among inpatients in tertiary hospitals in Bangladesh. METHODS: Between August and November 2022, we conducted a point prevalence survey in 4 tertiary hospitals in Dhaka, Bangladesh. The World Health Organization-directed point prevalence survey methodology and tools were followed for the data collection. Descriptive and multivariate statistics were performed using Stata version 15. RESULTS: Of 1,063 hospitalized patients, antibiotics were prescribed to 73.5% (781/1063, 95% confidence interval: 70.8-76.1) of patients. A total of 1,164 antibiotics were prescribed, and 49.1% of patients consumed multiple antibiotics. Only 31.4% of patients were prescribed antibiotics based on microbiology results. The reasons for antibiotic prescribing were mentioned only in 19.3% of patients. Infants (adjusted odds ratio: 8.52, P-value: <.001) and neonates (adjusted odds ratio: 4.32, P-value: <.001) were more likely to consume antibiotics compared to adults. Cephalosporins accounted for the majority (54.0%) of antibiotics used in hospitals. None of the hospitals had any antibiotic use guidelines. CONCLUSIONS: Consumption of Watch group antibiotics empirically among all age groups demonstrates irrational antibiotic usage in Bangladeshi hospitals. Implementation of a tailored stewardship program, antibiotic use guidelines, and prescriber-patient awareness could improve the rational use of antibiotics.

Freshwater pearl culture in Bangladesh: Current status and prospects.

Freshwater pearl farming is an emerging sector of aquaculture in Bangladesh which plays a growing role at major jewelry markets. With some improved techniques, high quality image or designer pearls are now produced from freshwater mussels Lamellidens marginalis. Yet it is difficult to reach in conclusion as the quantities produced, culture techniques used, and the upgrading of the existing culture technique are not well documented. Furthermore, many obstacles such as proper dissemination of culture technologies among the interested peoples, optimization of the culture environment and culture methods, standardization of breeding protocol and so on need to be addressed by the scientific community. This review article reports for the first time about the status of freshwater pearl culture in Bangladesh highlighting the fundamentals of pearl production, culture techniques used in farms, challenges, and prospects for upgradation of current culture principles in Bangladesh.

Size dependent ingestion and effects of microplastics on survivability, hematology and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus).

Microplastic pollution is drastically increasing in aquatic ecosystems and it is assumed that different sizes of microplastics have diverse impacts on the physiology of aquatic organisms. Therefore, this study was intended to examine the ingestion and size specific effects of polyamide microplastic (PA-MP) on different physiological aspects such as growth, feed utilization, survivability, blood parameters and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus). In a 28-day exposure, the fish were fed with different sized PA-MP with a concentration of 500 mg per kg of feed in order to simulate highly microplastic contaminated environment. Three different treatments were set for this experiment i.e. T1, 25-50 µm (smaller microplastic); T2, 300 µm-2 mm (larger microplastic); T3, (mixed) including a control (C); each had three replicates. The highest ingestion was recorded in the gastrointestinal tract (GIT) of fish exposed to smaller PA-MP treatments (T1 followed by T3). The results also showed compromised weight gain (WG; g), specific growth rate (SGR; %/day) and feed conversion ratio (FCR) with the exposure of PA-MP. Besides, survivability significantly reduced among treatments with the ingestion of smaller sized microplastic and found lowest in T1 (65.0 ± 5.0). In addition, the presence of PA-MP in feed negatively affected the concentration of hemoglobin and blood glucose. Similarly, smaller PA-MP caused most erythrocytic cellular and nuclear abnormalities; found highest in T1 that significantly different from other treatments (p < 0.05). Various histopathological deformities were observed in fish fed with PA-MP incorporated feed. The principal component analysis (PCA) showed that the toxicity and stress imparted by smaller PA-MP affected the survivability and blood parameters where larger PA-MP caused mild to severe abnormalities. Based on eigenvector values, the major abnormalities in intestine included occurrence of epithelium columnar degeneration (ECD: 0.402; PC1), hyperplasia of internal mucosa (HISM: 0.411; PC1), beheading of villi (BV: 0.323; PC1), atrophy of mucosa (AM: 0.322; PC1), tiny vacuoles in apical villi (TV: 0.438. PC2), crypt degeneration (CD: 0.375: PC2) and atrophy of goblet cell (AGC: 0.375; PC2). Therefore, it has been speculated that the size based PA-MP ingestion in the GIT interfered with the digestion and absorption as well as caused deformities that reflected negatively in survivability and hemato-biochemical parameters of juvenile striped catfish.

Lunar Age-Dependent Oscillations in Expression of the Genes for Kisspeptin, GnIH, and Their Receptors in the Grass Puffer during the Spawning Season.

Grass puffer is a semilunar-synchronized spawner: spawning occurs on beaches only for several days of spring tide around new moon (lunar age 0) and full moon (lunar age 15) every 2 weeks from spring to early summer. To investigate the role of kisspeptin and gonadotropin-inhibitory hormone (GnIH) in the semilunar-synchronized spawning, lunar age-dependent expression of the genes encoding kisspeptin (kiss2), kisspeptin receptor (kissr2), GnIH (gnih), GnIH receptor (gnihr), gonadotropin-releasing hormone 1 (GnRH1) (gnrh1), and three gonadotropin (GTH) subunits (gpa, fshb, lhb) was examined in the male grass puffer, which was kept in an aquarium under natural light condition in a lunar month during the spawning period. In the brain, both kiss2 and kissr2 showed lunar variations with a peak at lunar age 10, while both gnih and gnihr showed semilunar variations with two peaks at lunar age 0 and 20. On the other hand, gnrh1 showed semilunar variation with two peaks at lunar age 0 and 15. In the pituitary, kiss2, kissr2, gnih, and gnihr showed similar variations to those shown in the brain. The fshb and lhb mRNA levels showed semilunar variations with two peaks at lunar age 0 and 15. The present study shows lunar and semilunar oscillations of kiss2/kissr2 and gnih/gnihr expressions, respectively, with their peaks around spring tide in the brain and pituitary along with the semilunar expressions of gnrh1 and the pituitary GTH subunit genes. These results suggest that the lunar age-dependent expressions of the kisspeptin, GnIH, and their receptor genes may be primarily important in the control of the precisely timed semilunar spawning of the grass puffer.

Hypoxia alters the upper thermal limits and blood physiology in zebrafish, Danio rerio.

Hypoxic aquatic environments occur more frequently as a result of climate change, thereby exerting challenges on the physiological and metabolic functions of aquatic animals. In this study, a model fish, zebrafish (Danio rerio) was used to observe the climate-induced hypoxic effect on the upper thermal limit (critical thermal maximum; CTmax), hemoglobin, and blood glucose levels, and abnormalities of erythrocytes at cellular and nuclear level. The value of CTmax decreased significantly under hypoxia (39.10 ± 0.96 °C) compared to normoxia (43.70 ± 0.91 °C). At CTmax, hemoglobin levels were much lower (9.33 ± 0.60 g/dL) and blood glucose levels were significantly higher (194.20 ± 11.33 mg/L) under hypoxia than they were under normoxia and at the beginning of the experiment. Increased frequencies of abnormalities in the erythrocytes at both cellular (fusion, twin, elongated, spindle and tear drop shaped) and nuclear (micronucleus, karyopyknosis, binuclei, nuclear degeneration and notched nuclei) levels were also found under hypoxia compared to normoxia. These results suggest that hypoxic conditions significantly alter the temperature tolerance and subsequent physiology in zebrafish. Our findings will aid in the development of effective management techniques for aquatic environments with minimum oxygen availability.

Prevalence of microplastics in commonly consumed fish species of the river Old Brahmaputra, Bangladesh.

Microplastics (MPs) are pervasive in aquatic environments, but inland waterbodies (rivers and floodplains) have received much less attention. The present study assesses the incidence of MPs in the gastrointestinal tracts of five commercially important edible fish species-two column feeders (n = 30) and three benthivores (n = 45) from upstream, midstream, and downstream of the Old Brahmaputra river in north-central Bangladesh. MPs were detected in 58.93% of fish, with the highest level in freshwater eel, Mastacembelus armatus (10.31 ± 0.75/fish). Fibers (49.03%) and pellets (28.02%) were the most frequent MPs. Nearly 72% MPs were smaller than 1 mm, and 50.97% were black. FTIR analysis showed 59% polyethelene (PE), followed by polyamide (40%) and unidentified (1%). MP ingestion was linked to fish size and weight, and a high incidence was recorded in the downstream river. Two omnivorous benthic fish ingest more MPs than others. The results corroborate the presence of MPs in the inland river and fish fauna and augment our understanding of heterogeneous MP uptake by fish.

Bioaccumulation and Bioremediation of Heavy Metals in Fishes-A Review.

Heavy metals, the most potent contaminants of the environment, are discharged into the aquatic ecosystems through the effluents of several industries, resulting in serious aquatic pollution. This type of severe heavy metal contamination in aquaculture systems has attracted great attention throughout the world. These toxic heavy metals are transmitted into the food chain through their bioaccumulation in different tissues of aquatic species and have aroused serious public health concerns. Heavy metal toxicity negatively affects the growth, reproduction, and physiology of fish, which is threatening the sustainable development of the aquaculture sector. Recently, several techniques, such as adsorption, physio-biochemical, molecular, and phytoremediation mechanisms have been successfully applied to reduce the toxicants in the environment. Microorganisms, especially several bacterial species, play a key role in this bioremediation process. In this context, the present review summarizes the bioaccumulation of different heavy metals into fishes, their toxic effects, and possible bioremediation techniques to protect the fishes from heavy metal contamination. Additionally, this paper discusses existing strategies to bioremediate heavy metals from aquatic ecosystems and the scope of genetic and molecular approaches for the effective bioremediation of heavy metals.

Effects of probiotics on growth, survival, and intestinal and liver morphometry of Gangetic mystus (Mystus cavasius).

The usage of probiotics proved advantageous in aquaculture due to its positive impact on fish growth, immune response and environment. This study was aimed to assess the effects of probiotics on growth, survival and histometry of intestine and liver in Gangetic mystus (Mystus cavasius) using two separate experiments for a period of 8 weeks (in aquaria) and 16 weeks (in earthen ponds). Three different probiotic treatments were incorporated i.e. commercial probiotic one; CP-1 (T1), commercial probiotic two; CP-2 (T2), Lab developed (Lab dev.) probiotic (T3) including a control. The results indicated that the probiotics usage especially Lab dev. probiotic (T3) significantly improved the growth parameters such as weight gain (g) and specific growth rate (SGR, %/day) as well as ensured better feed conversion efficiency. Zero mortality was observed in aquaria whereas probiotic application enhanced survivability in earthen ponds. Moreover, all probiotic treatment exhibited positive results for different histo-morphometric features of intestine and liver. Mucus secreting goblet cells and fattening of mucosal fold increased significantly with probiotic usage. The amount of regular shaped nucleus was maximum in T3 with least intra cellular distance between liver tissues in earthen ponds. The greatest value for hemoglobin with lowest glucose level was observed in T3 as well. Furthermore, probiotic ensured low concentration of ammonia during culture. Overall, it was anticipated that the application of probiotics in Gangetic mystus culture resulted positive effect on its growth, feed utilization, survivability, histo-morphometry, immunity and hematological parameters.

Effects of dietary replacement of fish meal by soybean meal on growth, feed utilization, and health condition of stinging catfish, Heteropneustes fossilis.

Soybean meal (SBM) is a cost-effective alternative protein source to replace costly fish meal in aquaculture. This present study determined to measure the effects of replacing fish meal (FM) protein with SBM on growth, feed utilization, and health condition of stinging catfish, Heteropneustes fossilis. Four isonitrogenous (35 %) diets were applied in four treatment groups designed as SBM0, SBM25, SBM50, and SBM75, where 0 %, 25 %, 50 %, and 75 % of FM protein were substituted by SBM, respectively. Significantly higher mean final weight (g), weight gain (g), percent weight gain (%), specific growth rate (% day-1), and protein efficiency ratio (PER) were recorded in SBM0, SBM25, and SBM50 groups than SBM75 group. Consequently, significantly lower feed conversion ratio (FCR) was found in SBM0, SBM25, and SBM50 groups than SBM75 group. Moreover, protein content of whole-body carcass was significantly higher in SBM25 and lower in SBM0 group however, lipid content was significantly higher in SBM0 and SBM75 than in other groups. Hemoglobin, red blood cells, and white blood cells were significantly higher in SBM0, SBM25, and SBM50 groups compared to SBM75. However, the higher the substitution of FM protein by SBM in diets higher the values of glucose. Morphological analysis of the intestine including villi length (µm), width (µm), and area (mm2); crypt depth (µm); wall thickness (µm); abundance of goblet cell (GB); and muscle thickness (µm) showed an increasing trend in fish fed diet containing upto 50 % replacement of FM protein by SBM. Therefore, the results suggest that SBM could replace upto 50 % FM protein in diets of H. fossilis without compromising growth, feed efficiency, and health status.

Increase in temperature increases ingestion and toxicity of polyamide microplastics in Nile tilapia.

Microplastics (MP) pollution and global warming are worldwide concerns, creating various physiological problems for aquatic organisms. This study was carried out to know the effects of different temperature (30, 33 and 36 °C) on ingestion of MP along with the physiological consequences in Nile tilapia (Oreochromis niloticus) exposed to virgin polyamide (PA) (10 mg/L water; 500 µm to 4 mm in size) for 15 days. A significant difference was found in PA ingestion of the fish treated with different temperature. Fish from 36 °C temperature groups ingested highest amount of PA (136 ± 24.40 item/fish) during the exposure period. The hemoglobin (Hb) and red blood cell (RBC) decreased significantly in the highest temperature (36 °C) without PA exposure. At the same time, Hb increased, but RBC significantly reduced in all the temperature conditions with PA exposure. The number of white blood cell (WBC) and glucose level increased significantly in the highest temperature (36 °C) without PA exposure. In contrast, WBC increased and glucose decreased significantly in all the temperature conditions with PA exposure. Frequencies of various nuclear and cellular abnormalities of erythrocytes increased significantly in the fish exposed to all temperature with PA exposure, though severity increased with temperature. Similarly, histological damage of gills (hyperplasia, epithelial necrosis, deformed pillar system, epithelial lifting, telangiectasia) and intestine (epithelium breakage, enterocyte vacuolization and shortening of villi) was found to be mild to severe by the accumulation of PA, increased severity with increase of temperature. This study confirms that global warming as a consequence of climate change might influence MP ingestion hampering physiological state of fish.

Vitamin E supplementation in diet ameliorates growth of Nile tilapia by upgrading muscle health.

Vitamin E (VE), an important lipid-soluble antioxidant, has great influence on growth and maintenance in animal. The effects of VE supplemented diet on growth and feed usage in Nile tilapia (Oreochromis niloticus) was investigated in this study. Three formulated diets containing VE (0, 50 and 100 mg/kg) were fed to Nile tilapia (3.56 ± 0.16 g) in glass aquaria maintaining three replicate groups for 56 days (8 weeks). Survival, growth performance including weight gain, percent weight gain, and specific growth rate (WG, % WG, and SGR), and feed utilization comprising protein efficiency ratio and feed conversion ratio (PER and FCR) were calculated. Hemato-biochemical indices including hemoglobin level (Hb), white blood cell (WBC), red blood cell (RBC) and glucose level were analyzed. In addition, muscle morphology was examined after completion of the experiment. At the end of the trial, WG, %WG, SGR, FCR and PER increased significantly which had dietary VE supplimentation. However, no distinct changes were observed in Hb level, RBC count, WBC count and glucose level among these different dietary groups. Dietary VE treatments significantly upgraded the muscle fiber diameter and lowered the intra-muscle gap. Moreover, quantity of hyperplastic muscle fiber as well as nucleus also significantly enhanced by VE. Morphological structure of muscle characterized by a huge proportion of hyperplastic muscle that may be supposed to contribute the enhanced growth of Nile tilapia receiving VE supplemented diet. Therefore these results suggested that VE incorporation into the feed can be effective to improve the feed efficiency and maximize the growth of O. niloticus.

Dried fish more prone to microplastics contamination over fresh fish - Higher potential of trophic transfer to human body.

Globally, microplastics (MPs) contamination in aquatic organisms is emerging as an alarming phenomenon. In the present study, we investigated MPs in three commercially important fishes (Bombay duck Harpadon nehereus, ribbon fish Trichiurus lepturus and hairfin anchovy Setipinna phasa) in fresh and dried conditions collected from two sites (Chattogram and Kuakata) of the Bay of Bengal. It was evident that fresh T. lepturus ingested highest amount of MPs through the gills (6.41 mps/g) from Chattogram followed by in the gastrointestinal tract, GIT (6.20 mps/g) and in the muscle (1.20 mps/g) from Kuakata. Among the fresh fishes, H. nehereus from Kuakata accumulated highest amount of MPs (0.21 mps/g), while S. phasa from Kuakata contained the least amount of MPs (0.06 mps/g). On the other hand, among the dried fishes, T. lepturus from Kuakata contained highest amount of MPs (46.00 mps/g), while S. phasa from Kuakata retained lowest amount of MPs (2.17 mps/g). Strangely, all the dried fishes showed significantly higher amount of MPs compared to fresh fishes from both the locations. Fiber was the most dominant type of shape of MPs which accounted 66 %, followed by fragment (27.38 %), microbeads (3.59 %), film (1.48 %), foam (1.31 %) and pellet (0.25 %). Size-wise, the major portion (39.66 %) of MPs was present to be in size range less than 0.5 mm followed by 37.67 % in the size range of 0.5-1.0 mm group and rest 22.67 % within 1.0-5.0 mm. Red (41.55 %) colored MPs was the most prominent, followed by brown (22.11 %), blue (16.32 %), pink (11.69 %), purple (5.10 %), and green (2.25 %). Among polymer types, low-density polyethylene (LDPE) was the most common (38 %), followed by polystyrene (PS-22 %), polyvinyl chloride (PVC-16 %), polyamide (PA-13 %) and ethylene-vinyl acetate (EVA-9 %). The present study confirms high occurrence of MPs in the dried fishes over the fresh fishes from the Bay of Bengal, with high potential of trophic transfer to the human body.

Histopathological responses and recovery in gills and liver of Nile tilapia (Oreochromis niloticus) exposed to diesel oil.

Water pollution due to crude oil has become one of the major means of pollution lately. We experimented to study to what extent different concentrations of diesel oil can distress the gills and liver of the affected fish. Two groups of Nile tilapia (Oreochromis niloticus) were exposed to 0.1 ml/l and 0.5 ml/l diesel oil for seven days and then kept in pollutant-free water for 14 days to scrutinize how much they can recover. A control group has also maintained during the experiment. Several histo-pathological abnormalities were observed in gills including deformed pillar system, clubbed tips in the secondary lamellae, hyperplasia of the epithelial cells, aggregation of cells of the primary lamellae, fusion of secondary lamellae, telangiectasia and lamellar aneurysms. Though almost similar level of aberration was observed in the lower and higher treatment group, fish treated with lower concentrations were quick to recover. When it comes to the liver, fish treated with 0.1 ml/l diesel showed mild necrosis, patchy degeneration, hypertrophy nucleus and which eventually recovered after 14 days of the recovery period, whereas fish treated with 0.5 ml/l diesel showed moderate to severe abnormalities in almost all cases and the recovery was less but pattern was observed. The experimental study concluded that the higher the exposure to diesel oil, higher incidences of major health problems are recorded, seriously piercing the healing system of Nile tilapia.

Impacts of heavy metals on early development, growth and reproduction of fish - A review.

Heavy metals pollution causes a threat to the aquatic environment and to its inhabitants when their concentrations exceed safe limits. Heavy metals cause toxicity in fish due to their non-biodegradable properties and their long persistence in the environment. This review investigated the effects of heavy metals on early development, growth and reproduction of fish. Fish embryos/larvae and each developmental stage of embryo respond differently to the intoxication and vary from species to species, types of metals and their mode of actions, concentration of heavy metals and their exposure time. Many of the heavy metals are considered as essential nutrient elements that positively improve the growth and feed utilization of fishes but upon crossing the maximum tolerable limit these metals cause not only a hazard to fish health but also to human consumers and the disruption of ecological systems. Reduced gonadosomatic index (GSI), fecundity, hatching rate, fertilization success, abnormal shape of reproductive organs, and finally failure of reproduction in fish have been attributed to heavy metal toxicity. In summary, this review sheds light on the manipulation of fish physiology by heavy metals and seeks to raise sensitivity to the prevention and control of aquatic environmental contamination, particularly from heavy metals.

Multi-species probiotics improve growth, intestinal microbiota and morphology of Indian major carp mrigal Cirrhinus cirrhosus.

This study aimed to examine the effects of multi-species probiotic on growth, hematological status, intestinal microbes, and intestinal morphology of mrigal (Cirrhinus cirrhosus). The mrigal fries (average weight 0.51 g) were reared for 60 days by supplementing multi-species probiotics containing Bacillus spp. (1 × 109 cfu/mL) and Lactobacillus spp. (1 × 1011 cfu/mL) in the raising water at doses of 0 (control), 0.5, and 1.0 mL/L. The results indicated that fish reared with multi-species probiotics showed significantly higher growth performance and feed efficiency where the survival rate was similar in all cases. Accordingly, significant higher red blood cell (RBC) and white blood cell (WBC) were counted from the fish reared with multi-species probiotic. There was a considerable difference in bacterial microbiota between the experimental and control group. Multi-species probiotics significantly enhanced the length, width, and villus area. Several immune response indicators like fattening of intestinal mucosal fold, width of lamina propria, the width of enterocytes, and abundance of goblet cells were also increased significantly in fish that received multi-species probiotics. This study revealed that multi-species probiotics can significantly contribute to the growth of mrigal through upgrading intestinal microbiota and morphology, which can be suggested as an eco-friendly growth stimulator in mrigal farming.

Kisspeptin Exhibits Stimulatory Effects on Expression of the Genes for Kisspeptin Receptor, GnRH1 and GTH Subunits in a Gonadal Stage-Dependent Manner in the Grass Puffer, a Semilunar-Synchronized Spawner.

Kisspeptin has an important role in the regulation of reproduction by directly stimulating the secretion of gonadotropin-releasing hormone (GnRH) in mammals. In non-mammalian vertebrates, there are multiple kisspeptins (Kiss1 and Kiss2) and kisspeptin receptor types, and the two kisspeptins in teleosts have different effects depending on fish species and reproductive stages, serving reproductive and non-reproductive functions. In the grass puffer, Takifugu alboplumbeus, which has only a single pair of kiss2 and kissr2, both genes display seasonal, diurnal, and circadian oscillations in expression in association with the periodic changes in reproductive functions. To elucidate the role of kisspeptin in this species, homologous kisspeptin peptide (gpKiss2) was administered at different reproductive stages (immature, mature and regressed) and the expression levels of the genes that constitute hypothalamo-pituitary-gonadal axis were examined in male grass puffer. gpKiss2 significantly elevated the expression levels of kissr2 and gnrh1 in the brain and kissr2, fshb and lhb in the pituitary of the immature and mature fish. No noticeable effect was observed for kiss2, gnih, gnihr, gnrh2 and gnrh3 in the brain and gpa in the pituitary. In the regressed fish, gpKiss2 was ineffective in stimulating the expression of the gnrh1 and GTH subunit genes, while it stimulated and downregulated the kissr2 expression in the brain and pituitary, respectively. The present results indicate that Kiss2 has a stimulatory role in the expression of GnRH1/GTH subunit genes by upregulating the kissr2 expression in the brain and pituitary at both immature and mature stages, but this role is mostly ineffective at regressed stage in the grass puffer.

Blood biomarkers as diagnostic tools: An overview of climate-driven stress responses in fish.

Global climate change due to anthropogenic activities affects the dynamics of aquatic communities by altering the adaptive capacities of their inhabitants. Analysis of blood provides valuable insights in the form of a comprehensive representation of the physiological and functional status of fish under various environmental and treatment conditions. This review synthesizes currently available information about blood biomarkers used in climate change induced stress responses in fish. Alterations in informative blood-based indicators are used to monitor the physiological fitness of individual fishes or entire populations. Specific characteristics of fish blood, such as serum and plasma metabolites, cell composition, cellular abnormalities, cellular and antioxidant enzymes necessitate adapted protocols, as well as careful attention to experimental designs and meticulous interpretation of patterns of data. Moreover, the sampling technique, transportation, type of culture system, acclimation procedure, and water quality must all be considered for valid interpretation of hemato-biochemical parameters. Besides, blood collection, handling, and storage time of blood samples can all have significant impacts on the results of a hematological analysis, so it is optimal to perform hemato-biochemical evaluations immediately after blood collection because long-term storage can alter the results of the analyses, at least in part as a result of storage-related degenerative changes that may occur. However, the scarcity of high-throughput sophisticated approaches makes fish blood examination studies promising for climate-driven stress responses in fish.

Effects of heavy metals on fish physiology - A review.

The pollution by heavy metals poses a serious threat to the aquatic environment and to the organisms if the concentration of heavy metals in the environment exceeds the safe limits. Due to their non-biodegradable and long persistence nature in the environment, heavy metals cause toxicity in fish by producing oxygen reactive species through oxidizing radical production. In this review, we investigated the effects of heavy metals on fish physiology with special emphasis on hemato-biochemical properties, immunological parameters especially hormones and enzymes, histopathology of different major organs and underlying molecular mechanisms. All those parameters are significantly affected by heavy metal exposure and are found to be important bio-monitoring tools to assess heavy metal toxicity. Hematological and biochemical alterations have been documented including cellular and nuclear abnormalities in different fish species exposed to different concentrations of heavy metals. Major fish organs (gills, liver, kidneys) including intestine, muscles showed different types of pathology specific to organs in acute and chronic exposure to different heavy metals. This study also revealed the expression of different genes involved in oxidative stress and detoxification of heavy metals. In a nutshell, this article shades light on the manipulation of fish physiology by the heavy metals and sought attention in the prevention and maintenance of aquatic environments particularly from heavy metals contaminations.

Response and recovery of Nile tilapia exposed to diesel oil - Behavioral, hemato-biochemical and morphological changes of erythrocytes.

Pollution caused by petroleum oil in several manners is becoming a threat to aquatic ecosystem. Hence, we carried out an experiment to investigate how diesel oil affects biota behavior, physiological attributes and how they recover by using Nile tilapia (Oreochromis niloticus) as a model organism. Nile tilapia of two different treatment groups were exposed to 0.1 mL/L and 0.5 mL/L diesel oil for 7 days. Then both groups were kept in completely diesel oil-free water for 14 days. A control group was maintained throughout the experimental period. We examined the behavioral attributes, hemato-biochemical parameters: hemoglobin (Hb), red blood cell (RBC), white blood cell (WBC) and glucose (Glu), and morphological changes of erythrocytes after diesel exposure and at the end of recovery phase. Our results revealed that there were abnormalities in behavior and significant changes in Hb, RBC, WBC and Glu level in both of the treatment group after 7 days of exposure. Frequencies of erythrocytic cellular abnormalities (ECAs), for example, twin, spindle, elongated, tear drop and erythrocytic nuclear abnormalities (ENAs) like notch nuclei, karyopyknosis, nuclear bud and nuclear bridge were prominent in both groups. However, the amount of anomalies was higher in most if not all the cases in 0.5 mL/L treatment group. Nile tilapia of both groups were quick to recover but the 0.1 mL/L group showed profound recovery than the 0.5 mL/L group. However, in the cases of ECAs and ENAs, recovery of the 0.5 mL/L group was insignificant. Hence, our experimental study concluded that the higher the exposure to diesel oil, higher incidences of major health problems are recorded, seriously piercing the healing system of Nile tilapia.

Presence of microplastics in two common dried marine fish species from Bangladesh.

We examined microplastics (MP) in two commercially important dried fish, Bombay duck (Harpadon nehereus) and ribbon fish (Trichiurus lepturus), collected from two sites on the Bay of Bengal (Cox's Bazar and Kuakata). The number of MP found in dried Bombay duck and ribbon fish from Kuakata was significantly higher (41.33 g-1 and 46.00 g-1, respectively) than the MP present in samples collected from Cox's Bazar (28.54 g-1 and 34.17 g-1, respectively). Fibers were the most common type of MP identified in all samples (41-64%), followed by fragments (22-34%), microbeads (9-16%), films (3-4%), foams (1-4%), and pellets (0-2%). ATR-FTIR analysis revealed three different types of MP polymer - polyethylene (35-45%), polystyrene (20-30%) and polyamide (30-45%) in the dried fish samples. The study confirms the presence of high MP loads in dried fish from the Bay of Bengal, with high potential of trophic transfer of MP to the human body.