Characterization of the somatostatin system in tilapia: implications for growth and reproduction.

Somatostatin (SST) plays diverse physiological roles in vertebrates, particularly in regulating growth hormone secretion from the pituitary. While the function of SST as a neuromodulator has been studied extensively, its role in fish and mammalian reproduction remains poorly understood. To address this gap, we investigated the involvement of the somatostatin system in the regulation of growth and reproductive hormones in tilapia. RNA sequencing of mature tilapia brain tissue revealed the presence of three SST peptides: SST6, SST3, and low levels of SST1. Four different isoforms of the somatostatin receptor (SSTR) subfamily were also identified in the tilapia genome. Phylogenetic and synteny analysis identified tiSSTR2-like as the root of the tree, forming two mega clades, with SSTR1 and SSTR4 in one and SSTR2a, SSTR3a, and SSTR5b in the other. Interestingly, the tiSSTR-5 isoforms 5x1, 5x2, and 5x3 were encoded in the sstr3b gene and were an artifact of misperception in the nomenclature in the database. RNA-seq of separated pituitary cell populations showed that SSTRs were expressed in gonadotrophs, with sstr3a enriched in luteinizing hormone (LH) cells and sstr3b significantly enriched in follicle-stimulating hormone (FSH) cells. Notably, cyclosomatostatin, an SSTR antagonist, induced cAMP activity in all SSTRs, with SSTR3a displaying the highest response, whereas octreotide, an SSTR agonist, showed a binding profile like that observed in human receptors. Binding site analysis of tiSSTRs from tilapia pituitary cells revealed the presence of canonical binding sites characteristic of peptide-binding class A G-protein-coupled receptors. Based on these findings, we explored the effect of somatostatin on gonadotropin release from the pituitary in vivo. Whereas cyclosomatostatin increased LH and FSH plasma levels at 2 h post-injection, octreotide decreased FSH levels after 2 h, but the LH levels remained unaffected. Overall, our findings provide important insights into the somatostatin system and its mechanisms of action, indicating a potential role in regulating growth and reproductive hormones. Further studies of the complex interplay between SST, its receptors, and reproductive hormones may advance reproductive control and management in cultured populations.

Irisin promotes tilapia muscle cell growth and amino acid uptake via IGF-1 signaling.

Irisin is a recently discovered myokine that facilitates the browning of white adipose tissue, increases glucose uptake in skeletal muscle, and influences metabolic processes in the liver. However, its potential effects on amino acid absorption remained largely unexplored. This study aimed to elucidate the role of irisin in modulating amino acid uptake and delineate the underlying molecular mechanisms involved. To this end, juvenile tilapia were administered intraperitoneal irisin injections at 100 ng/g body weight over 8 weeks. Evaluation of various physiological parameters revealed that irisin supplementation significantly improved the specific growth rate and feed conversion efficiency while reducing feed consumption. Muscle tissue analysis revealed that irisin significantly modified the proximate composition by increasing protein content and reducing lipid levels. It also significantly raised the levels of both essential and non-essential amino acids in the muscle. Histological analysis demonstrated that irisin-stimulated muscle growth through hyperplasia rather than hypertrophy, corroborated by upregulated IGF-1 mRNA and downregulated myostatin mRNA expression. Mechanistic studies in cultured tilapia muscle cells elucidated that irisin activated integrin receptors on muscle cells, which subsequently engaged IGF-1/IGF-1R signaling. Downstream of IGF-1R activation, irisin simultaneously stimulates the ERK1/2 and PI3K/mTORC2/Akt pathways. The convergence of these pathways upregulates L-type amino acid transporter 1 expression, thereby augmenting amino acid uptake into muscle cells. In summary, irisin supplementation in tilapia leads to improved muscle growth, predominantly via hyperplasia and augmented amino acid assimilation, governed by intricate cellular signaling pathways. These findings provide valuable aquaculture applications and novel insights into muscle development.

Comprehensive insights into the mechanism of flavor formation driven via inoculation with mixed starter cultures in dry-fermented tilapia sausages: Integration of macrogenomics, volatilomics, and lipidomics.

To investigate the mechanisms of flavor formation in dry-fermented tilapia sausages, the volatiles, bacterial community, and lipid composition during fermentation were analyzed using gas chromatography-ion mobility spectrometry, 16S high throughput sequencing, and ultra-performance liquid chromatography-mass spectrometer. Pediococcus pentosaceus, Staphylococcus xylosus, and Staphylococcus carnosus became dominant bacteria during the fermentation. A total of 66 volatiles and 293 lipids (48 differential lipids) were identified. PC and PE content decreased. Aldehyde and 1-octen-3-ol content decreased. Most esters and ketones content increased during fermentation. Six metabolic pathways associated with differential lipids were identified by enrichment analysis. Glycerophospholipid metabolism was the main metabolic pathway. Correlation analysis revealed that PC and PE were precursors for volatiles, including PC 16:0/18:2 and PE 18:0/22:6. The dominant bacteria facilitate the hydrolysis of PC and PE, leading to the formation of esters and ketones. This study provides a theoretical basis for the targeted regulation of fermented sausage flavors.

Optimizing nutrient utilization, hydraulic loading rate, and feed conversion ratios through freshwater IMTA-aquaponic and hydroponic systems as an environmentally sustainable aquaculture concept.

Water quality in land-based fish production can be controlled through either instantaneous water exchange or costly wastewater treatment followed by recirculation. Agricultural-aquaculture integration is an excellent alternative technique for reducing nutrient discharge levels, boosting profitability, and converting fish culture wastewater into valuable products. The current study employed a solar energy system to power two separate IMTA-aquaponics systems (Nutrient Film Technique, NFT, and Floating Raft Systems, FRS) for the cultivation of Nile tilapia, African catfish, thin-lipped grey mullet, freshwater crayfish, freshwater mussels, and a variety of vegetables. Tilapia and catfish were fed exclusively on diets under the IMTA system. All wastewater from tilapia and catfish ponds, both dissolved and solid, flows sequentially to ponds containing other cultivated species. The water then flows through the IMTA system's terminal point to the NFT and FRS systems before returning to the tilapia and catfish ponds, allowing complete control of the nutrient flow throughout this entire circular system. Two 147-day production cycles were concluded. The results from the second production cycle are reported. Total biomass gain for aquatic species in the IMTA system was 736.46 kg, compared to 145.49 kg in the tilapia and 271.01 kg in the catfish monoculture systems. The current IMTA system had a cumulative feed conversion ratio (FCR) of 0.90, while the FCRs for tilapia and catfish were 1.28 and 1.42, respectively. Nile tilapia and catfish consumed 571.90 kg of feed containing 25.70 kg of nitrogen (N) and 9.70 kg of phosphorus (P), reflecting, and gaining 11.41 and 3.93 kg of dietary N and P, representing 44.40 and 40.46% dietary N and P retention, respectively. In the IMTA system, the addition of mullet and prawn as detrivores aquatic animals improves dietary N and P utilization efficiency to 59.06 and 51.19%, respectively, while the addition of mussels as herbivore animals improves dietary N and P utilization efficiency to 65.61 and 54.67%, respectively. Finally, using FRS and NFT as hydroponic systems increased dietary N and P efficiency to 83.51% N and 96.82% P, respectively. This study shows that the IMTA-Aquaponic system, as a bio-integrated food production system, can convert the majority of fish-fed residues into valuable products suitable for desert, rural, and urban areas in impoverished and developing countries.

Use of natural peptide TP4 as a food preservative prevents contamination by fungal pathogens.

Molecules of natural origin often possess useful biological activities. For instance, the natural peptide Tilapia Piscidin 4 (TP4) exhibits potent antimicrobial activity against a broad spectrum of pathogens. In this study, we explored the potential application of TP4 as a food preservative, asking whether it can prevent spoilage due to microbial contamination. A preliminary in silico analysis indicated that TP4 should interact strongly with fungal cell membrane components. Hence, we tested the activity of TP4 toward Candida albicans within fruit juice and found that the addition of TP4 could abolish fungal growth. We further determined that the peptide acts via a membranolytic mechanism and displays concentration-dependent killing efficiency. In addition, we showed that TP4 inhibited growth of Rhizopus oryzae in whole fruit (tomato) samples. Based on these findings, we conclude that TP4 should be further evaluated as a potentially safe and green solution to prevent food spoilage.

Investigating the optimum stocking density of tilapia (Oreochromis niloticus) for intensive production focused to in-pond raceway system.

The primary objective of this trial was to study the effects of stress caused by stocking density in tilapia (Oreochromis niloticus) cultured in the in-pond raceway system (IPRS). Fingerlings (Initial body weight = 30.00 ± 1.20 g) were reared at different stocking densities i.e. low stocking density (n = 13,000; 1.77 kg/m3), medium stocking density (MSD) (n = 17,000; 2.32 kg/m3), and high stocking density (HSD) (n = 21,000; 2.86 kg/m3), all confined within the raceways of the IPRS. Each group was studied in triplicates. The observed growth revealed a regression in the HSD treatment, evident in its reduced weight gain per fish per day, in contrast to other treatments. Survival rate across all treatments was above 99%. Notably, the HSD treatment exhibited an elevated level of cortisol; however, this intensified crowding stress did not significantly undermine the nutritional value of the fish in HSD and other experimental treatments. Furthermore, an elevation in the levels of superoxide dismutase, catalase, and glutathione peroxidase was noted within the HSD treatment in comparison to the other treatments to reduce the damage caused by reactive oxygen species. As the trial proceeded, functions of digestive enzymes like amylase, protease, and lipase diminished consistently across all treatments. This could possibly signify a deliberate redirection of energy resources toward stress alleviation rather than the usual digestive processes. In summation, it can be reasonably deduced that a stocking density of approximately 2.32 kg/m3 (MSD) emerges as the optimal threshold for effectively cultivating tilapia within an intensive aquaculture framework.

Determination of Growth Indicators of Tilapia sparrmanii (Smith, 1840) in Molepo Dam, South Africa.

<b>Background and Objective:</b> The sustainable management and conservation of fish biodiversity depends on studying fish biology. In this study, the length-weight relationships and condition factors of <i>Tilapia sparrmanii</i> were observed to gain a better understanding of their ecological and nutritional conditions. This information is crucial for the effective management of fisheries. <b>Materials and Methods:</b> During the study, 100 <i>T. sparrmanii</i> were collected from the Molepo Dam from October, 2022 to March, 2023. This fish's condition factor (CF) and length-weight relationship (LWR) were studied. To determine the size of each fish, the total length was measured using a caliper with a precision of 0.1 mm and the weight using a balance with an accuracy of 0.1 g. Differences were analyzed using ANOVA with the Tukey's <i>post hoc</i> test. A non-parametric Chi-square test was employed to evaluate the differences in sexes each month. <b>Results:</b> Their total length and body weight ranged from 4-15 cm and 0.96-57.96 g, respectively. The study found a strong positive relationship between the length and weight of the fish (r = 0.96). The regression coefficient (b) was more than 3.0, indicating a positive allometric growing rate. The condition factors (K) of males and females were not significantly different (p>0.05). The lowest CF value was observed in March (K = 1.01±0.03) and the highest in December (K = 1.73±0.12). The sex ratio of 1.0 male to 1.15 female was observed, which was significantly different from the theoretical ratio of one male to one female. This suggests that males were not significantly more than females (p>0.05). <b>Conclusion:</b> The study found that <i>T. sparrmanii</i> in Molepo Dam exhibited allometric growth, as evidenced by a strong correlation between length and weight represented by a high "r" value. This fish is in good condition because it has no competition for food due to ecological factors.

Improvement mechanism of volatile flavor in fermented tilapia surimi by cooperative fermentation of Pediococcus acidilactici and Latilactobacillus sakei: Quantization of microbial contribution through influence of genus.

Single starter can hardly improve the volatile flavor of fermented fish surimi. In this study, the changes of volatile compounds (VCs) and microbial composition during cooperative fermentation of Latilactobacillus sakei and Pediococcus acidilactici were studied by headspace solid-phase microextraction gas chromatography-mass spectrometry and 16S rRNA gene high-throughput sequencing. During cooperative fermentation, most VCs and the abundance of Latilactobacillus and Lactococcus significantly increased, while Pediococcus, Acinetobacter, and Macrococcus obviously decreased. After evaluation of correlation and abundance of each genus, Latilactobacillus and Lactococcus possessed the highest influence on the formation of volatile flavor during cooperative fermentation. Compared with the natural fermentation, cooperative fermentation with starters significantly enhanced most of pleasant core VCs (odor activity value≥1), but inhibited the production of trimethylamine and methanethiol, mainly resulting from the absolutely highest influence of Latilactobacillus. Cooperative fermentation of starters is an effective method to improve the volatile flavor in the fermented tilapia surimi.

Multiple trait comparison and global intestine transcriptional provide new insights into bases of heterosis in hybrid tilapia (Oreochromis niloticus × Oreochromis aureus).

Heterosis has been utilized in aquaculture for many years, yet its molecular basis remains elusive. Therefore, a comprehensive analysis of heterosis was conducted by comparing growth, digestion and biochemistry indices, as well as the intestinal gene expression profiles of Nile tilapia, blue tilapia and their hybrids. The results revealed that hybrid tilapia demonstrated an enhanced growth traits and elevated digestive enzyme activity compared to Nile and blue tilapia. Additionally, the hybrid tilapia displayed superior antioxidants and non-specific immune levels, with increased levels of catalase (CAT), alkaline phosphatase (AKP), acid phosphatase (ACP), glutathione (GSH), superoxide dismutase (SOD), total antioxidant capacity (TAOC), lysozyme, and immunoglobulin M (IgM) relative to Nile and blue tilapia. Moreover, 3392, 2470 and 1261 differentially expressed genes (DEGs) were identified in the intestinal tissues when comparing Nile tilapia to blue tilapia, hybrid tilapia to blue tilapia, and hybrid tilapia to Nile tilapia. Upon classifying the differentially expressed genes (DEGs), non-additively expressed DEGs accounted for 68.1 % of the total DEGs, with dominant and over-dominant expressed DEGs comprising 63.7 % and 4.4 % in the intestines, respectively. These non-additively expressed DEGs were primarily associated with metabolic, digestive, growth, and developmental pathways. This enrichment enhances our comprehension of the molecular underpinnings of growth heterosis in aquatic species.

The potential use of daphnia meal as substitute for fishmeal in diets of hybrid red tilapia affects growth performance, activities of digestive enzymes, antioxidant, immune status and intestinal histological parameters.

The current study aimed to evaluate growth performance, digestive enzyme activities, antioxidant status, nonspecific immune response and intestinal histological status of red tilapia fed Daphnia meal (DM) as a substitute for fishmeal (FM). Hybrid red tilapia (Oreochromis mossambicus × Oreochromis aureus) fry (0.54 ± 0.05 g fish-1) was allocated in nylon haba cages (100 fry m-3) for 2 weeks as an acclimation period. The fish were divided into five groups (three replicates each). The experimental diets were prepared by replacing FM with DM at concentrations of 25%, 50%, 75% and 100% respectively. The results indicated that fish fed increasing levels of DM (50%-75%) experienced high growth performance, feed utilisation and protein content. The activities of digestive enzymes were significantly increased in all groups fed DM diets compared to the control. The antioxidant balance was improved by decreasing the level of malondialdehyde and increased the total antioxidant capacity, catalase, superoxide dismutase and glutathione reductase activities in the liver of fish fed DM. The nonspecific immune response, including lysozyme, alkaline phosphatase activities and total protein level improved significantly with increasing FM substitution levels by DM in a dose-dependent manner. Histometric analysis of the intestinal wall revealed an increase in the villus length, crypts depth and goblet cells number in groups fed DM meal up to 50% substitution level compared to other treatments. It may be concluded from results of this feeding trial that in the aquaculture of hybrid tilapia, FM may be substituted with up to 50% DM without compromising intestinal health, growth performance and immune status of the fish.

Modulation of growth performance, feed utilization, and physiological traits in redbelly Tilapia (Tilapia zillii) through environmental and sex-based interactions.

This study explored the combined influence of tank color, stocking density, and gender on Tilapia zillii's performance and well-being. In this 120-day trial, 320 T. zillii, each initially weighing 10.0 ± 0.1 g/fish, were distributed among 24 tanks. The experiment included eight distinct treatment combinations, varying tank color (blue and green), stocking density (10 and 30 fish/m3) and sex (monosexual and mixed). The results showed that blue tanks improved specific growth rate and condition factor, while green tanks were better for feed utilization. Density at 30 fish/m3 showed the highest mean values of final body weight and total length, weight gain (WG), and gain length. Mono-sex outperformed mixed-sex ones in WG and daily growth. Interactions between color, density and sex were significant, affecting growth and feed utilization. Green tanks were best for protein profiles, while blue tanks excelled in glucose. A density of 10 fish/m3 yielded the highest protein profiles, and mono-sex fish had higher protein profiles. For lipid profiles, green tanks were superior, and density affected lipid profiles. Mixed-sex populations were best for certain lipid profile parameters. Interactions between these factors also played a significant role, making the biochemical profiles of T. zillii a complex interplay of various factors. The results explored that tank color, fish density and sex influence the activity of nonspecific immune enzymes in the liver of T. zillii. Blue tanks and lower fish density led to higher nonspecific immune enzymes, while mono-sex fish exhibited more significant nonspecific immune enzymes. Complex interactions between these factors also influenced nonspecific immune enzyme activities. Blue tanks increased malondialdehyde (MDA) levels, while green tanks raised glutathione S-transferases (GST) and catalase (CAT) levels. Lower fish density led to higher MDA, while higher density increased GST and CAT. Mono-sex fish had more MDA and GST, while mixed-sex fish showed greater CAT levels. Complex interactions among these factors affected the antioxidant levels in T. zillii. In summary, our study suggests that rearing T. zillii in green tanks at higher densities (30 fish/m3) and in mono-sex conditions yields the best results in terms of growth and overall performance.

Morphometric and gut microbial evaluation of Tilapia (Oreochromis niloticus) fed on different levels of Moringa oleifera.

In current study, different feeding levels of Moringa oleifera formulated diet was compared to analyze the growth performance, feed conversion ratio, feed conversion efficiency and gut microbiology of Oreochromis niloticus. The study was comprised of four treatment groups including 4%, 8% and 12% Moringa oleifera and one control group which was devoid of Moringa leaves. The experimental trial was conducted at the Zoology laboratory of Pakistan Institute of Applied and Social Sciences, (PIASS) Kasur. The physicochemical parameters of water such as temperature, dissolve oxygen, pH, total dissolved solids and salinity in all aquaria were found non-significantly different from each other. In control condition T1, the average weight gain was 14.89±16.90a grams, while average length gain was 11.52±7.444a cm. However, the total viable count on Eosin methylene blue was 7.4×107, 5.8×107 on Tryptic soy agar and 5.8×107on Nutrient agar. In T2, the average weight gain was 16.22±16.09b grams and average length gain was 12.97±7.79b cm. The total viable count on Eosin methylene blue was 7×107, 5.5×107 on Tryptic soy agar and 5.8×107on Nutrient agar. In T3, the average weight gain was 37.88±27.43c grams, while the average length gain was recorded as 16.48±12.56c cm. However, the total viable count for treatment 3 was 6.4×10 on Eosin methylene blue, 4.8×107 on Tryptic soy agar and 5.2×107on Nutrient agar. In T4, the average weight gain was 44.22±31.67d grams, while the average length gain was 15.25±10.49d cm. The total viable count was 4.3×107on Eosin methylene blue, 3.1×107 on Tryptic soy agar and 3.8×107 on Nutrient agar. The effect of Moringa oleifera on the growth of Oreochromis niloticus was found to be significant and 12% Moringa extract showed maximum length and weight gain and minimum feed conversion ratio with the least microbial count in fish intestine.

Effects of dietary leucine and valine levels on growth performance, glycolipid metabolism and immune response in Tilapia GIFT Oreochromis niloticus.

An 8-week feeding trial was performed to evaluate the effects of dietary leucine (Leu) and valine (Val) levels on growth performance, glycolipid metabolism and immune response in Oreochromis niloticus. Fish (15.23 ± 0.05 g) were randomly fed four diets containing two Leu levels (1.2% and 2.3%) and two Val levels (0.7% and 1.4%) as a 2 × 2 experimental design (LL-LV, LL-HV, HL-LV and HL-HV). Compared with LL-LV group, the growth parameters (final weight, daily growth coefficient (DGC) and growth rate per metabolic body weight (GRMBW)), feed conversion rate (FCR), the activities of intestinal amylase, lipase, creatine kinase (CK) and Na+, K+-ATPase, liver NAD+/NADH ratio, as well as the expression of SIRT1, GK, PK, FBPase, PPARα, CPT IA, ACO and IL10 all increased significantly in the HL-LV group; however, in the high Val group, final weight, DGC, GRMBW, intestinal enzyme activities, as well as the expression of PEPCK, SREBP1, FAS, IL8 and IL10 of the HL-HV group were significantly lower than those of the LL-HV group, while the opposite was true for the remaining indicators. Significant interactions between dietary Leu and Val were observed in final weight, DGC, GRMBW, plasma IL1ß and IL6 levels, intestinal amylase and CK activities, liver NAD+/NADH ratio, as well as the expression of SIRT1, PK, PEPCK, FBPase, SREBP1, FAS, PPARα, CPT IA, ACO, NF-κB1, IL1ß, IL6 and IL10. The highest values of growth parameters, intestinal enzyme activities and expression of SIRT1, FBPase, PPARα, CPT IA and ACO were observed in the HL-LV group, while the opposite was true for the expression of SREBP1, FAS, PPARα, NF-κB1, IL1ß and IL6. Overall, our findings indicated that dietary Leu and Val can effect interactively, and fish fed with diets containing 2.3% Leu with 0.7% Val had the best growth performance and hepatic health status of O. niloticus.

Mathematical model for predicting oxygen concentration in tilapia fish farms.

The main aim of this research is to develop a mathematical model to predict the dissolved oxygen in recirculating aquaculture system. The oxygen consumption of the model through the fish respiration and nitrification and the oxygen addition of the model through oxygen generator and water pumping. The effect of different water temperatures (24, 26, 28, 30 and 32 °C) on the dissolved oxygen consumption through fish respiration, biofilter and nitrification and fish growth were studied. An experiment to measure oxygen consumed by fish respiration and biofilteration and fish growth with the growth period and to validate the model results was carried out. The oxygen consumption predicted by the model was in a good agreement with those measured by the system. The oxygen consumption by fish respiration ranged 12.04 to 47.53 g O2 m-3 h-1 experimentally, while it was from 12.01 to 46.06 g O2 m-3 h-1 theoretically. The predicted and measured oxygen consumption through biofilteration values ranged from 0.43 to 21.91 and 0.45 to 23.09 g O2 m-3 h-1, respectively. The individual fish weight from the system ranged from 3.00 to 209.52 g experimentally while it was from 3.00 to 226.25 g theoretically during the whole period.

Evaluation of Cyanobacterial Bloom from Lake Taihu as a Protein Substitute in Fish Diet-A Case Study on Tilapia.

The utility of cyanobacterial bloom is often hindered by concerns about the toxin content. Over three years of investigation, we found that the toxin content of cyanobacterial bloom in Lake Taihu was always low in June and higher in late summer and autumn. The findings enabled us to compare the effects of diets containing low and high toxic cyanobacterial blooms on the growth and consumption safety of tilapia. There were no negative effects on the growth of tilapia, and the muscle seemed to be safe for human consumption in the treatment of 18.5% low toxic cyanobacterial bloom. Therefore, limitations of the utilization of cyanobacterial biomass can be overcome by selecting low toxic cyanobacterial bloom that can be found and collected in large lakes.

Interactive effects of freshwater acidification and selenium pollution on biochemical changes and neurotoxicity in Oreochromis mossambicus.

Effect of selenium and acidification in freshwater environment was assessed solitary but no reports are available on the impacts of both factors act together. In the present study, effects of combined simultaneous exposure to selenium (Se) and low pH were assessed in Mozambique tilapia, Oreochromis mossambicus. Responses were measured based on antioxidant defenses (enzymatic SOD, CAT, GPx and non-enzymatic GSH), biotransformation enzyme (GST), metallothionein levels (MT), oxidative damage (LPO, CP), Na+/K+-ATPase (NKA) activity in gills and liver tissues and neurotoxicity (acetylcholinesterase, AChE) response in brain tissue. Fish were exposed to combined treatment at different pH levels (7.5, control (optimum pH for tilapia growth); 5.5, low pH) and Se concentrations (0, 10, and 100 µg L-1). Toxicity levels of Se were not significantly different under control and low pH indicating that pH did not affect Se toxicity. Levels of GSH and MT were enhanced in Se-exposed fish at both pH. Combined effects of high Se concentration and low pH decreased SOD and CAT activities and increased those of GPx and GST. However, organisms were not able to prevent cellular damage (LPO and CP), indicating a condition of oxidative stress. Furthermore, inhibition of Na+/K+-ATPase activity was showed. Additionally, neurotoxicity effect was observed by inhibition of cholinesterase activity in organisms exposed to Se at both pH conditions. As a result, the combined stress of selenium and freshwater acidification has a slight impact on antioxidant defense mechanisms while significantly inhibiting cholinesterase and Na+/K + -ATPase activity in fish. The mechanisms of freshwater acidification mediating the toxic effects of trace non-metal element on freshwater fish need to investigate further.

DNA Damage in Liver Cells of the Tilapia Fish Oreochromis mossambicus Larva Induced by the Insecticide Cyantraniliprole at Sublethal Doses During Chronic Exposure.

Cyantraniliprole can effectively control lepidopteran pests and has been used all over the world. In general, the risk of cyantraniliprole seems low for fish, but the toxicity selectivity among different fish species was not clear. Here, we present the methods for the acute toxicity and chronic effects of cyantraniliprole by using juvenile tilapia (Oreochromis mossambicus). Based on this test, 96 h LC50 of cyantraniliprole to tilapia was 38.0 mg/L. After exposed for 28 days, specific growth rates of the blank control, solution control, and the treatments of 0.037, 0.37 and 3.7 mg/L of cyantraniliprole were 1.14, 0.95, 0.93, 0.82, and 0.70% per day, respectively. The results of micronucleus experiment and single cell gel electrophoresis showed that cyantraniliprole damaged DNA in liver cells of tilapia larvae. Quantitative PCR results showed that cyantraniliprole could induce the upregulation of Rpa 3 that is responsible for the DNA repair. The significant downregulation of Chk 2 gene was related to p53 pathway. It is therefore proposed that cyantraniliprole causes DNA damage in liver cells of tilapia and activates DNA damage and repair pathways.

miR-133b targets tagln2 and functions in tilapia oogenesis.

microRNAs (miRNAs) are important components of non-coding RNAs that participate in diverse life activities by regulating gene expression at the post transcriptional level through base complementary pairing with 3'UTRs of target mRNAs. miR-133b is a member of the miR-133 family, which play important roles in muscle differentiation and tumorigenesis. Recently, miR-133b was reported to affect estrogen synthesis by targeting foxl2 in mouse, while its role in fish reproduction remains to be elucidated. In the present study, we isolated the complete sequence of miR-133b, which was highly expressed in tilapia ovary at 30 and 90 dah (days after hatching) and subsequently decreased at 120 to 150 dah by qPCR. Interestingly, only a few oogonia were remained in the antagomir-133b treated tilapia ovary, while phase I and II oocytes were observed in the ovaries of the control group. Unexpectedly, the expression of foxl2 and cyp19a1a, as well as estradiol levels in serum were increased in the treated group. Furthermore, tagln2, an important factor for oogenesis, was predicted as the target gene of miR-133b, which was confirmed by dual luciferase reporter vector experiments. miR-133b and tagln2 were co-expressed in tilapia ovaries. Taken together, miR-133b may be involved in the early oogenesis of tilapia by regulating tagln2 expression. This study enriches the understanding of miR-133b function during oogenesis and lays a foundation for further study of the regulatory network during oogenesis.

An application of Bayesian Belief Networks to assess management scenarios for aquaculture in a complex tropical lake system in Indonesia.

A Bayesian Belief Network, validated using past observational data, is applied to conceptualize the ecological response of Lake Maninjau, a tropical lake ecosystem in Indonesia, to tilapia cage farms operating on the lake and to quantify its impacts to assist decision making. The model captures ecosystem services trade-offs between cage farming and native fish loss. It is used to appraise options for lake management related to the minimization of the impacts of the cage farms. The constructed model overcomes difficulties with limited data availability to illustrate the complex physical and biogeochemical interactions contributing to triggering mass fish kills due to upwelling and the loss in the production of native fish related to the operation of cage farming. The model highlights existing information gaps in the research related to the management of the farms in the study area, which is applicable to other tropical lakes in general. Model results suggest that internal phosphorous loading (IPL) should be recognized as one of the primary targets of the deep eutrophic tropical lake restoration efforts. Theoretical and practical contributions of the model and model expansions are discussed. Short- and longer-term actions to contribute to a more sustainable management are recommended and include epilimnion aeration and sediment capping.

Impact of high dietary cornstarch level on growth, antioxidant response, and immune status in GIFT tilapia Oreochromis niloticus.

This study was conducted to investigate the relationship between different cornstarch levels in tilapia diet and immune function. All test fish were fed with three cornstarch levels: low-cornstarch (0, LS), medium-cornstarch (18%, MS) and high-cornstarch (36%, HS) diets. Three hundred and sixty fish (initial mean body weight 31.73 ± 1.36 g) were randomly allocated into twelve water-circulated tanks, and thirty fish per tank. Compared with the low and medium cornstarch diets, the results of growth showed that the high cornstarch diet significantly decreased the FBW, WGR, and SGR, and increased the FCR of tilapia (P < 0.05). The high cornstarch diet significantly decreased the content of crude protein and increased the content of crude lipid in whole body composition (P < 0.05). Moreover, the VSI and CF in HS diet were significantly higher than those of LS diet (P < 0.05). The results of blood biochemical index exhibited that the HS diet significantly increased the content of blood glucose, and liver/muscle glycogen (P < 0.05). The results of antioxidant experiments demonstrated that the content of SOD and T-AOC in MS diet were significantly higher than those of HS diet (P < 0.05). Meanwhile, the content of MDA in MS diet was significantly lower than that of HS diet (P < 0.05). The results of immune index test showed that the lysozyme activities in the serum, liver, and gill, and the phagocytic activity and index in MS diet were significantly higher than those of HS diet (P < 0.05). The challenge assay results revealed that the mortality rate of HS diet was higher than those of LS and MS diets, but the difference was not significant (P > 0.05). In conclusion, the overall results suggested that the 36% cornstarch diet reduced not only the growth performance, but also body immunity. Under this experimental condition, GIFT tilapia could tolerate 18% cornstarch, but not 36% cornstarch.