Male Tilapia Research Articles

Determination of Biochemical Responses of Genetically-male Tilapia (Oreochromis niloticus) after Replacing Fish Oil with Plant-based Oils in Their Diets

This study evaluated biochemical responses of genetically male tilapia after replacing fish oil with plant-based oils in their diets. The sources of oils were coconut, olive, crude palm, sunflower and sesame seed. These oils were incorporated at 7% level and were used to formulate five isonitrogenous (42.5% CP) diets. In the control experiment (sixth diet) fish oil was used. Fish were reared in 1 m x 1 m x 1 m floating net-hapa. Feeing trial lasted for 12 weeks. At the end of the experiment, blood samples were collected and tested for serum protein, electrolytes and tissue lipid peroxidation. Results of the study revealed that the ratio of albumin to globulin was statistically similar (p > 0.05) in all fish group examined. The results of serum electrolyte showed that olive oil treated fish recorded the highest (p < 0.05) level. The amount of malondialdehyde (MDA) formed in fish tissues increased (p < 0.05) in sunflower oil group by 69%, 43%, 20% and 32% in the liver, kidney, gills and heart respectively. This indicated that reactive oxygen species may be associated with the metabolism of sunflower oil leading to peroxidation of membrane lipids of the respective organs. However, this level of MDA deposition had not been associated with any negative effects on fish health. Inferences from this study conclusively support the direct use of these plant oils as total replacement for fish oil in diets of Oreochromis niloticus.

Effect of exposure to palm oil mill effluent on reproductive impairment of male Nile Tilapia (Oreochromis niloticus, Linnaeus 1758)

One of the negative impacts arising from the existence of palm oil mill industries is the increase of pollution from Palm Oil Mill Effluent (POME), particularly for the aquatic environment. This study was conducted to investigate the reproductive impairment of male Nile tilapia (Oreochromis niloticus Linnaeus 1758) after exposed to POME. An experiment of a chronic test was carried out using a completely randomized design consisting four treatments with five replication: control (0 mg/L POME), treatment A (1.565 mg/L POME), treatment B (2.347 mg/L POME), and treatment C (3.130 mg/L POME). The exposure of POME was performed for 45 days. Reproductive hormone concentration, gonadosomatic index and spermatocrite value in each treatment statistically analyzed by using one-way analysis of variance (ANOVA). Results showed that the POME exposure had no significant impact on estradiol and testosterone concentrations (p>0.05), but, it triggered a decline in the progesterone concentration (p<0.05). Progesterone concentration decreased significantly from 0.57 ± 0.24 ng/mL in control to 0.28 ± 0.04 ng/mL in treatment C. The hormonal decline resulted in a significant decrease in gonadosomatic index and spermatocrite of male Nile Tilapi (p<0.05). In conclusion, exposure to POME induced reproductive impairment in male Nile Tilapia.

Proximate composition of male and female African catfish (Clarias gariepinus) and tilapia (Tilapia zilli) in Jega river, Kebbi state, Nigeria

Fish is highly nutritious, tasty, and easily digestible. It is much sought after by a broad cross-section of the world’s population, particularly in developing countries as it provides the cheapest protein source. Nigeria is blessed with numerous inland freshwater rivers and lakes scattered all over the country. This freshwater habitat consists of many species of fish that have successfully dominated all niches over time and have for many reasons remained unstudied. The situation concealed a lot of scientific information particularly on food security and safety to the inmates and the country at large. Jega River which transcended many States in the North-Western part of Nigeria to open into the river Niger is one of such rivers largely uncared for, study-wise. African catfish (Clarias gariepinus) and Tilapia (Tilapia zillii) have been wisely selected for the present proximate composition studies. The juveniles of these fishes were purchased from local fishermen in Mariner Waje landing site of the river which flows by Jega town, a local government area in Kebbi State, Nigeria. For the study, the methodology approved by the Association of Official Analytical Chemists (AOAC) was used to determine the proximate composition of the fishes. The highest percentage crude protein content of 49.18 ± 0.30% was observed in juvenile female C. gariepinus; while the lowest protein content of 39.22± 0.50% was observed in juvenile male T. zilli. The highest percentage lipid content of 11.75± 1.50% was observed in juvenile female tilapia; while the lowest percentage lipid content of 6.25± 0.29% was observed in male African catfish. The highest percentage fibre content of 4.00 ± 0.29% was observed in male and female C. gariepinus, while the lowest percentage fibre content of 0.75± 0.29% was observed in male tilapia. There were variations (p< 0.05) when the protein and lipid contents of both the species were compared with each other. There was also a significant difference (p< 0.05) when the carbohydrate contents were compared between the fish species, but there was no significant difference (p > 0.05) when the fibre content was compared within the species. The analyses showed that both the male and female fish species studied had high protein contents.

Residual impact of 17α-methyltestosterone and histopathological changes in sex- reversed Nile tilapia (Oreochromis niloticus)

Objective: To examine sex reversal both by oral and by immersion using 17α-methyltestosterone on the methyltestosterone residual concentration and the organ histopathology of tilapia fish. Methods: This study used oral and immersion treatment methods for sex reversal of tilapia fish and used normal fish as the control and each treatment was repeated 4 times. 17α-methyltestosterone at dosages of 60 mg/kg feed and 0.5 mg/L were used for oral and immersion methods, respectively. In the first step, tilapia fry were reared at 100 L aquaria, with a density of 1 fish/L for 2 months. In the next step, male tilapias were reared at happa (net cage) of (2×1×1) m3 size in the controlled pond, with a density of 30 fish/happa for 3 months. The methyltestosterone residual concentrations were analyzed by one-way analysis of variance and Duncan’s multiple range tests, while organ histopathology was analyzed by descriptive method. Results: Residual concentrations in the serum of methyltestosterone- treated fish were significantly lower than that in normal fish, especially in 4- and 5-month-old tilapias with averages of less than 5 μg/L, while in normal fish was more than 5 μg/L. In the flesh, methyltestosterone residual concentrations showed relatively no significant differences between the oral and immersion treatment groups and methyltestosterone-treated fish remained lower compared to normal fish, except in 5-month-old tilapia. Methyltestosterone-treated tilapia exhibited histopathological changes on gill, liver, kidneys, and intestine organs. Conclusions: Sex reversal either by oral or by immersion has methyltestosterone residual concentration, but does not exceed the limits (5 μg/L or 5 μg/kg) of synthetic steroid on the fish body, although methyltestosterone causes histopathological changes on gill, liver, kidneys, and intestine.

Changes in vitellogenin and estrogen receptor expression and 17β-estradiol concentration in male juvenile tilapia can be used to evaluate endocrine-disrupting chemicals

The effects of endocrine disruption with respect to potential human toxicities have been extensively evaluated to date. However, the standard testing methods used have not always taken the most pertinent approach. In this study, we used juvenile male tilapia (Oreochromis niloticus) as an animal model to test for endocrine disruption by chemicals. We measured 17β-estradiol (E2) concentrations, and the mRNA relative expression ratio (RER; treatment/control) of vitellogenin (vtg2) and estrogen receptors (ERs) to assess whether the effluent concentration of selected plasticizers disrupt E2 function in fish. We found that the vtg2 RER was significantly increased after exposure to 2.52 nM E2 for 5 days, 0.438 μM of bisphenol A (BPA) for 7 days, or 2.865 μM Cd2+ for 7 days. These data support vtg2 transcript level as a sensitive biomarker to evaluate contamination of water by endocrine disrupting chemicals (EDCs). However, vtg2 expression did not respond to fluctuations of E2 concentrations in the tilapia juveniles exposed to selected plasticizers. However, the RER of three types of ERs appeared to change dramatically upon exposure to plasticizers. ERα significantly increased, but ERβ2 decreased with 3.6 μM DEP exposure. Both ERα and ERβ2 decreased significantly after 1.44 μM DIBP exposure. We suggest that changes of vtg2 mRNA RER, E2 levels and ERs mRNA expression should be taken into consideration at the same time to determine if chemical contaminants in the water are endocrine disrupters.

Photoperiodic effects in blood glucose, cortisol, hematological parameters and reproductive indexes of gift lineage reversed male tilapia

The objective of this study was to evaluate the influence of the photoperiod on the physiological, hematological and reproductive parameters of tilapia males of the GIFT lineage. The treatments differed in the simulations of emeral photoperiods T1 = 0L: 24E T2 = 24L: 0E, T3 = 12L: 12E. Each aquarium was considered an experimental unit. In the present study, tilapia males under different photoperiods did not present significant differences in gonad weight and gonadosomatic index. At the end of the experiment, there were also no significant differences in hepatosomatic indexes (IHS) of Tilapia males under different treatments. In the present experiment, it was observed that the 0L: 24E treatment obtained a shorter testicular length in relation to the other treatments. In addition, the Tilapia submitted to 24L: 0E presented significant difference for the glucose levels, and did not present significant difference for cortisol levels and survival rate compared withthe other treatments. There were no statistical differences for hematological values. Exposure to different light regimes has shown that for GIFT tilapia, the photoperiod that promotes better reproductive index and well-being conditions is the photoperiod (12L: 12E).

Transcription of the Sox30 Gene Is Positively Regulated by Dmrt1 in Nile Tilapia.

The Sox family member Sox30 is highly expressed in the testis of several vertebrate species and has been shown to play key roles in spermiogenesis. However, its transcription regulation remains unclear. Here, we analyzed the Sox30 promoter from the teleost fish Nile tilapia (Oreochromis niloticus) and predicted a putative cis-regulatory element (CRE) for doublesex and mab-3 related transcription factor 1 (Dmrt1), a male-specific transcription factor involved in male sex differentiation. Transcriptional profiling revealed that Sox30 and Dmrt1 similarly exhibited a high expression in tilapia testes from 90 days after hatching (dah) to 300 dah, and the transcription of the Sox30 gene was reduced about one-fold in the testes of male tilapia with Dmrt1 knockdown. Further dual-luciferase reporter assay confirmed that Dmrt1 overexpression significantly promoted transcriptional activity of the Sox30 promoter and this promotion was decreased following the mutation of putative CRE for Dmrt1 within the Sox30 promoter. Chromatin immunoprecipitation-based PCR (ChIP-PCR) and electrophoretic mobility shift assay (EMSA) demonstrated that Dmrt1 directly binds to putative CRE within the Sox30 promoter. These results together indicate that Dmrt1 positively regulates the transcription of the tilapia Sox30 gene by directly binding to specific CRE within the Sox30 promoter.

The role of social and/or ecological contexts influences assessment strategy use in Tilapia

AbstractAnimals engage in costly agonistic contests during which winners procure resources. During these interactions, the combatants obtain and use information to make decisions on whether to persist or to withdraw from the fight, which is termed assessment. Recent theory and work have suggested that the types of assessment employed may be more variable than previously thought, with the use of different strategies possibly being influenced by social and ecological conditions during priming. This study addresses the contextual components (social and ecological) that affect the utilization of one assessment strategy over another. Male tilapia were primed with different combinations of social (large and small animals) and ecological (resource rich or poor) contexts 24 hr prior to fighting in staged, dyadic contests. When opponents were primed with the same context, a clear assessment strategy emerged and differed as a function of priming treatment. Conversely, when fish were primed with different treatment contexts, there was no discernible assessment. In addition, priming conditions had differing effects for large and small fish. Thus, assessment strategies in cichlids are dependent upon a combination of social, ecological contexts and size of the animal. Since assessment strategies change as a function of both of these contexts, as well as others, future framework investigating assessment strategies should include both intrinsic and extrinsic factors that may shape fighting dynamics.

A Preliminary Survey of Estrogenic Effects in Cultured Adult Male Nile Tilapia (Oreochromis niloticus) in the Seven Lakes of San Pablo City, Philippines

This study aimed to investigate the impact of estrogenic endocrine disruptors in adult male Nile Tilapia (Oreochromis niloticus) from the Seven Lakes (Bunot, Calibato, Mohicap, Palakpakin, Pandin, Sampaloc and Yambo) of San Pablo City in Laguna, Philippines. Fish were collected from aquaculture operations in each lake from July to September 2017 and examined for plasma vitellogenin (VTG) levels, hepatosomatic index (HSI) and gonadosomatic index (GSI). In comparison to the reference group (Pandin Lake), fish from Mohicap, Sampaloc and Yambo had higher levels of plasma VTG. HSI was increased in fish from Bunot Lake while it was markedly reduced in fish from Sampaloc Lake. Comparable GSI were obtained in all samples. While most examined fish are in active spermatogenesis, fish from Sampaloc Lake had immature gonads with no spermatozoa, and with minimal to moderate Leydig cell vacuolation and hyperplasia. The results suggest that cultured Nile tilapia from Sampaloc Lake is most adversely affected by endocrine-active compounds. The identification and quantification of these chemicals are recommended in future studies.

Effects of replacement of fish oil by sesame seed (<i>Sesamum indicum L.</i>) oil in the diets of til-aqua natural male tilapia

This study evaluated the effects of dietary sesame oil extracted from autoclaved, roasted and fermented sesame seed meal on growth, nutrient utilization and muscle fatty acid composition of Til-aqua natural male tilapia. Four isonitrogenous (crude protein content: 35%) and iso-energetic (Gross energy: 19.36 KJ/g) diets were formulated to contain 3% of either fish oil (FO) or oils extracted from autoclaved (AO), roasted (RO) or fermented (FEO) sesame seed meals. Each diet was assigned to duplicate groups of Til-aqua natural male tilapia (initial average weight, 2.78±0.02 g) using recirculating aquaculture systems for 56 days. Specific growth rate 0.8 (2.93%/day) and metabolic growth rate (9.68 g/kg /day) recorded in the group fed RO diet were significantly lower (P<0.05) than those of AO treatment. Muscle fatty acid compositions were consistent with their dietary values except for di-homo-γ-linolenic acid, 20:3 (n-6), which accumulated in the groups that received diets FO (58.11%), FEO (44.75%) and RO (23.30%). There was a significant increase (P<0.05) in the muscle content of palmitic acid of the group fed diet AO (26.6%) when compared with the control (7.30%), diet RO (18.74%) and diet FEO (11.43%). The study showed that sesame oil can replace fish oil in the diets of tilapia without compromise on growth or nutrient utilization. Keywords : Fish oil, Sesame seed oil, Fatty acid, Tilapia, Nutrient digestibility

Maskulinisasi ikan nila (Oreochromis niloticus) melalui pemberian propolis yang dicampur dalam pakan buatan

This study was conducted to determine the optimal dose of propolis for male sex reversal in tilapia larvae through mixing in artificial feed. This research was carried out at the Aquaculture Technology Laboratory, Faculty of Fisheries and Marine Sciences, Sam Ratulangi University. The experimental fish was taken from Board of Freshwater Fisheries Aquaculture at Tatelu. As many as 4,000 individuals fish aging 5 days were acclimatized for 2 days in an aquarium measuring 60 x 40 x 40 cm. After the acclimatization process was terminated, the larvae density was set to 100 per aquarium. Furthermore, the fish were fed with treatment feed previously added with propolis with a dose of A (0 mL/kg of feed) as a control, B (0.9 mL/kg of feed), C (1.8 mL/kg of feed), D (2.7 mL/kg of feed) and t E (3.6 mL/kg of feed). Treatment feed was given to larvae twice a day for 28 days. The results showed that masculinization of tilapia using propolis mixed into artificial feed had a very significant effect on the percentage of male tilapia and survival. In this study treatment C (1.8 mL/kg of feed) and treatment D (2.7 mL/kg of feed) resulted in the highest percentage of male tilapia which was 81.33% and 88.00% respectively. This shows that the administration at 1.8 mL/kg in artificial feed has a very real and effective effect on masculinization.Keywords: Oreochromis niloticus, masculinization, sex reversal, propolis

Exclusion of two microsatellite markers in the sex-linkage study of Nile tilapia (Oreochromis niloticus L.)

Monosex Nile tilapia (Oreochromis niloticus) is highly preferred in semi-intensive and intensive culture systems to prevent uncontrolled reproduction and to obtain fast growing male. Production of all male tilapia is being practiced by the hatcheries of Bangladesh mainly by administering androgen hormones (particularly 17-α-methyl-testosterone) with feed in a mixture of undifferentiated fry for about a month. The direct application of hormone to such food chain often arises question in respect to public health and safety. The alternative to this is the production of putative supermales, a rather safe but longer procedure to obtain all male progeny. However, sex determination system in tilapia is fairly complex. Recent developments have resulted in a linkage map and genetic markers that can be used to analyze the sex determination system. For genetic analysis of different genotypes of fish, microsatellite DNA marker ARO120 and ARO121 were used for studying the inheritance pattern for possible sex linkage using Polyacrylamide gel electrophoresis. In case of ARO120, it was observed that the Dam XX was heterozygous; 11 out of 22 female progeny and 10 out of 22 male progeny were found to be heterozygous. In case of ARO121, it was observed that the Dam XX was heterozygous; 16 out of 22 female progeny and 20 out of 22 male progeny were found to be heterozygous. Though the marker polymorphisms were observed in this study, these were excluded from the sexlinkage study due to limited extent of information as sex-linked markers in Nile tilapia BFRI strain. This study provides a baseline for further research using other suitable polymorphic markers for assisting marker-assisted selection.&#x0D; Res. Agric., Livest. Fish.6(1): 143-151, April 2019

Transcriptomic and epigenomic alterations of Nile tilapia gonads sexually reversed by high temperature

Tilapia males are favored by the farming industry due to faster growing and higher body weights in a given period than females, and increasing the male proportion is desired for breeding. Previous studies indicate that high temperature treatment could sporadically transform genetic females of Nile tilapia to become phenotypic males, while the mechanism is unclear.Here, we treated female Nile tilapia with high temperature at early developmental stage, and obtained sex reversed pseudo-male (i.e. masculinized female) fish with morphologically male gonads. Transcriptome sequencing and whole genome methylation analyses were performed on gonads from normal males, females and pseudo-males. The profiles of gene expression and CpG methylation were compared. The results suggested that pseudo-males exhibited strikingly similar gene expression and methylation patterns with genetic males, but highly distinct from females. The differentially expressed genes between pseudo-males and other groups revealed a possibility that alterations in the “potassium ion transportation” processes might play important roles in sex reversal of female tilapia upon high temperature treatment. Our study provided a landscape of global gene expression and methylation status in the heat induced masculinized pseudo-male tilapia.

SAT-LB069 Differential Regulation of Hypothalamic and Hepatic Reproductive Signals by Leptin and Sex Steroids in the Mozambique Tilapia Oreochromis mossambicus

Reproduction is a physiologically demanding process that relies on energy sufficiency, the lack of which can result in delayed puberty and suppression of reproductive function. The pleiotropic peptide hormone leptin is a key signal in energy homeostasis that relays information on peripheral energy availability to central circuits. In mammals, leptin has been found to serve as a critical permissive signal in the activation of the gonadotropic axis and onset of puberty. Although leptin effects on reproduction have been explored extensively in mammals, its actions and regulatory properties on reproduction in fishes remain unclear. The current study assesses (i) the effect of in vivo leptin treatment on hypothalamic kisspeptin (kiss2) and gonadotropin-releasing hormone (gnrh1), (ii) the effect of leptin treatment on major egg-yolk precursors, vitellogenins (vtga, vtgb, vtgc), and insulin-like growth factor (igf1) in primary tilapia hepatocytes, and (iii) the effect of sex steroid treatment on leptin (lep) and insulin-like growth factor in primary tilapia hepatocytes. Gene expression of lep in the liver, the primary source of circulating hormone, increased with gonadosomatic index and sexual maturation of male and female tilapia, suggesting the hormone may regulate reproductive function. Intraperitoneal injection and 6-hour treatment with recombinant tilapia leptin (rtLep) in adult male tilapia resulted in increased hypothalamic kiss2 and gnrh1 transcript levels versus saline control (P < 0.01). In primary hepatocyte culture, rtLep suppressed vtgb and vtgc transcript levels (P < 0.01), while it stimulated igf1 (P < 0.0001). Testosterone and estradiol reduced lep levels (P < 0.001), but disparately regulated ­igf1 whereby testosterone increased igf1 and estradiol decreased igf1 at 10 and 100 nM (P < 0.001). The non-aromatizable 11-ketotestosterone increased lep and igf1 transcript levels at 100 nM (P < 0.05). Our findings suggest that leptin expression rises with sexual maturation and the hormone exerts stimulatory effects on hypothalamic gonadotropic factors. By contrast, leptin reduces estrogen-sensitive vitellogenesis while promoting elements of the somatotropic axis (e.g., igf1), suggesting the hormone may have dual roles in regulating reproductive and somatic growth processes. We speculate that this latter effect may be associated with limiting energy partitioning to reproduction in instances of negative energy balance. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

THE DEVELOPMENT, PURIFICATION AND CHARACTERIZATION OF ANTI- VITELLOGENIN ANTIBODIES RAISED IN HENS (GALLUS GALLUS DOMESTICUS) AGAINST TILAPIA (OREOCHROMIS NILOTICUS) VITELLOGENIN PROTEIN

ABSTRACT This study was conducted to induce, isolate and characterize and determine the role of Vitellogenin (Vtg) which is used as a biomarker of environmental quality and steroidogenesis in oviparous organisms. We have purified Vtg from male adult tilapia scientifically known as Oreochromis niloticus previously treated with estradiol 5 μg/g body weight (BW). By using ion exchange chromatography Vtg was purified from blood plasma yielding 1.13 mg Vtg/ml. Subsequently, Lohmann Brown hens were immunized at a 125 and 100 μg Vtg/ml, including three antigen treatments of booster doses of 75 and 50 μg Vtg/ml, respectively. At day 30 post-immunization, posture eggs were collected, we have successfully optimized the extraction of anti-VtgIgY antibody. The purified anti-VtgIgY was validated with SDS-PAGE, detecting heavy and light chains of 70 kDa and 30 kDa, respectively. Further, we have developed ELISA using anti-VtgIgY. To estimate the Vtg specificity, commercial anti-Vtg antibodies of dorada (Sparusaurata) were used and validated for tilapia by Western Blot. Detection of the Vtg monomer was at a dilution of 1/2000 IgY primary antibody. The antibodies thus obtained through the conventional techniques of production and validation of IgY antibodies for Vtg of tilapia demonstrate that they are viable under local conditions, can be successfully used for programs of environmental monitoring and reproduction control in oviparous species.

Interaction of Temperature, Dissolved Oxygen and Feed Energy on Growth Performance of All Male Tilapia Fingerlings

Interaction of Temperature, Dissolved Oxygen and Feed Energy on Growth Performance of All Male Tilapia Fingerlings

Exposure of male tilapia (Oreochromis niloticus) to copper by intraperitoneal injection: DNA damage and larval impairment

The present work aimed to assess the genotoxic effects of intraperitoneally injected copper in males of O. niloticus, and to investigate its association with eventual changes in the quality of the gametes and in the generation of offspring abnormalities. Thus, to evaluate DNA damage, the alkaline comet assay was performed in sperm and blood; sperm parameters were analyzed to determine the quality of the gametes, and the incidence of morphological abnormalities of larvae, originated from eggs fertilized by males exposed to copper, was used as a measure of reproductive impairment. Male fish were exposed to three doses (1 mg/kg, 2 mg/kg, 4 mg/kg) of copper sulfate via intraperitoneal injection and observed after 96 h of exposure. We found that the quality of gametes was not affected by copper, as indicated by the lack of differences in sperm parameters between the exposed and the control groups. Nonetheless, copper induced an increase in sperm DNA damage at all tested doses. Taking into consideration the total number of abnormalities, larvae presented a higher proportion of morphological abnormalities at all the tested doses. Considering the morphological abnormalities separately, the 2 mg/kg and 4 mg/kg groups presented significantly higher frequencies of arrested development and spinal abnormalities than the control group. This work suggests that intraperitoneally injected copper is an inductor of DNA breakage in germ cells of O. niloticus males. Copper induces the formation of larval morphological abnormalities, causing reproductive impairment to this species. The fact that copper did not induce alterations on sperm parameters indicates that the parental genotoxic effects are inheritable to the offspring.

Effects of Probiotics on Growth and Production of Monosex Tilapia (Oreochromis Niloticus) in Nylon Net Cages at Dekar Haor, Sunamganj, Bangladesh

To assess the effect of probiotics on growth, survival rate and production performance of all monosex tilapia (Oreochromis niloticus) for a period of 120 days in 2016 in nylon net cages placed in Dekar haor of Sunamganj district. The study was categorized into four treatments as T1 (brand a), T2 (brand b), T3 (brand c) and T4 (control) based on probiotics and each having three replicates. Cages were stocked with nursed male tilapia fry at a density of 35 nos./m3 with average size of 14.33 ± 6.41 - 16.33 ± 3.15 g. Tilapia of all the cages were fed with commercial mega floating feed at a decreasing rate of 10 - 5% of total biomass thrice daily. Feed was supplemented with probiotics at a rate of 0.5 g/kg. Comparatively higher growth (307.33 ± 33.92 g), survival rate (97.6 ± 4.90%), yield (10.5 ± 1.15 kg/m3), net profit (Tk.798.96 ± 90.85/m3) and lower food conversion ratio (1.16) were secured in T3 than that of other treatments, which were manifolds higher than the earthen freshwater and brackish waterbodies. Therefore, results of the study reveal that probiotics may be used in aquaculture for increasing fish production.&#x0D; Asiat. Soc. Bangladesh, Sci. 44(1): 69-78, June 2018

Transcriptome analysis reveals novel insights into the response of low-dose benzo(a)pyrene exposure in male tilapia

Despite a wide number of toxicological studies that describe benzo[a]pyrene (BaP) effects, the metabolic mechanisms that underlie these effects in fish are largely unknown. Of great concern is the presence of BaP in aquatic systems, especially those in close proximity to human activity leading to consumption of potentially contaminated foods. BaP is a known carcinogen and it has been reported to have adverse effects on the survival, development and reproduction of fish. The purpose of this study was to investigate if a low dose of BaP can alter genes and key metabolic pathways in the liver and testis in male adult tilapia, and whether these could be associated with biological endpoints disruption. We used both high-throughput RNA-Sequencing to assess whole genome gene expression following repeated intraperitoneal injections of 3 mg/kg of BaP (every 6 days for 26 days) and morphometric endpoints as indicators of general health. Condition factor (K) along with hepatosomatic and gonadosomatic indices (morphometric parameters) were significantly lower in BaP-treated fish than in controls. BaP exposure induced important changes in the gene expression pattern in liver and testis as revealed by both Pathway and Gene Ontology (GO) analyses. Alterations that were shared by both tissues included arachidonic acid metabolism, androgen receptor to prostate-specific antigen signaling, and insulin-associated effects on lipogenesis. The most salient liver-specific effects included: biological processes involved in detoxification, IL6-associated insulin resistance, mTOR hyperactivation, mitotic cytokinesis, spindle pole and microtubule binding. BaP effects that were confined to the testis included: immune system functions, inflammatory response, estrogen and androgen metabolic pathways. Taken together, gene expression and morphometric end point data indicate that the reproductive success of adult male tilapia could be compromised as a result of BaP exposure. These results constitute new insights on the mechanism of action of low dose BaP in a non-model organism (tilapia).

Alterations of cytochrome P450 and the occurrence of persistent organic pollutants in tilapia caged in the reservoirs of the Iguaçu River

Environmental chemicals originating from human activities, such as persistent organic pollutants (POPs), may interfere with the endocrine system of aquatic organisms. The effect of these chemicals on biota and human populations is of high public concern but remains poorly understood, especially in aquatic environments of South America. The aim of this study was to investigate the bioavailability of POPs and the related effects in caged male tilapia (Oreochromis niloticus) in four cascading reservoirs of the Iguaçu River, Southern Brazil. POPs including organochlorine pesticides (OCPs), polychlorinated biphenyl (PCBs), and polybrominated diphenyl ethers (PBDEs) were determined in the reservoir water and tissue samples of tilapia after two months of exposure. The PCB levels in water (14.7 ng L−1) were 14 times higher than the limits permitted by the Brazilian legislation in the Salto Santiago (SS) reservoir. Similarly, concentrations of aldrin and its metabolites (6.05 ng L−1) detected in the water sample of the Salto Osório (SO) reservoir were also above the permitted limits. RT-qPCR analysis revealed different transcript levels of cytochrome P450 enzymes (CYP1A and CYP3A) in the liver among the four groups, with induced activity in tilapia from the SS reservoir. Quantification of the CYP3A mRNA expression and catalytic activity showed higher values for fish caged at the SS reservoir. The fish from this site also had a higher number of eosinophils observed in the testes. Although overt measurements of endocrine disruption were not observed in caged fish, alteration of CYP enzymes with co-occurrence of organochlorine contaminants in water may suggest bioavailability of contaminants from agricultural sources to biota. Additional studies with feral or caged animals for a longer duration may be necessary to evaluate the risks of the waterways to humans and wildlife.