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.

Recent research has raised concern about the biocompatibility of iron oxide nanoparticles (IONPs), as they have been reported to induce oxidative stress and inflammatory responses, whilst prolonged exposure to high IONP concentrations may lead to cyto-/genotoxicity. Besides, there is concern about its environmental impact. The aim of our study was to investigate the effects of IONPs on the antioxidant defence system in freshwater fish Mozambique tilapia (Oreochromis mossambicus, Peters 1852). The fish were exposed to IONP concentration of 15 mg/L over 1, 3, 4, 15, 30, and 60 days and the findings compared to a control, unexposed group. In addition, we followed up the fish for 60 days after exposure had stopped to estimate the stability of oxidative stress induced by IONPs. Exposure affected the activity of antioxidant and marker enzymes and increased the levels of hydrogen peroxide and lipid peroxidation in the gill, liver, and brain tissues of the fish. Even after 60 days of depuration, adverse effects remained, indicating long-term nanotoxicity. Moreover, IONPs accumulated in the gill, liver, and brain tissues. Our findings underscore the potential health risks posed to non-target organisms in the environment, and it is imperative to establish appropriate guidelines for safe handling and disposal of IONPs to protect the aquatic environment.
Nedavna istraživanja izazvala su zabrinutost oko biokompatibilnosti nanočestica željezova oksida (engl. iron oxide nanoparticles – IONP), nakon što je utvrđeno da izazivaju oksidacijski stres i upalni odgovor, a produljena izloženost visokim koncentracijama IONP-a može dovesti do cito-/genotoksičnosti. Osim toga, postoji i zabrinutost u pogledu njihova utjecaja na okoliš. Cilj ovog istraživanja bio je proučiti djelovanje IONP-a na antioksidacijski obrambeni sustav slatkovodne ribe mozambičke tilapije (Oreochromis mossambicus, Peters 1852). Ribe su bile izložene koncentraciji IONP-a od 15 mg/L tijekom 1, 3, 4, 15, 30 i 60 dana, a usporedno su praćene i jedinke kontrolne, neizložene skupine. Nadalje, praćenje je nastavljeno tijekom 60 dana nakon prestanka izloženosti kako bismo procijenili stabilnost oksidacijskoga stresa izazvanoga IONP-om. Izloženost je utjecala na aktivnost antioksidacijskih i markerskih enzima te povećala razine vodikova peroksida i lipidne peroksidacije u tkivu ribljih škrga, jetre i mozga. Čak i nakon 60 dana „čišćenja“ zaostali su štetni učinci, koji upozoravaju na nepovratnu nanotoksičnost. Štoviše, IONP se akumulirao u tkivu škrga, jetre i mozga. Naša otkrića naglašavaju potencijalne zdravstvene rizike za neciljane organizme u okolišu, te je nužno uspostaviti odgovarajuće smjernice za sigurno rukovanje i odlaganje IONP-a kako bi se zaštitio vodeni okoliš.

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.

BACKGROUND: Trace elements play a crucial role in fish nutrition, with zinc (Zn) being one of the most important elements. BIO-sourced zinc nanoparticles were synthesized using the green microalga Pediastrum boryanum (BIO-ZnNPs, 29.35 nm). 30 or 60 mg/ kg dry feed of the BIO-ZnNPs (BIO-ZnNPs30 and BIO-ZnNPs60) were mixed with the Nile tilapia (Oreochromis niloticus) basal diet and fed to the fish for 8 weeks to evaluate their impact on fish growth, digestion, intestinal integrity, antioxidative status, and immunity.
RESULTS: A significant enhancement was observed in all investigated parameters, except for the serum protein profile. BIO-ZnNPs at 60 mg/kg feed elevated the activities of reduced glutathione (GSH) and catalase (CAT), enzymatic antioxidants, but did not induce oxidative stress as reflected by no change in MDA level. Fish intestinal immunity was improved in a dose-dependent manner, in terms of improved morphometry and a higher count of acid mucin-producing goblet cells. Interleukin-8 (IL-8) was upregulated in BIO-ZnNPs30 compared to BIO-ZnNPs60 and control fish groups, while no significant expressions were noted in tumor necrosis factor-alpha (TNFα), nuclear factor kappa B (NFkB), and Caspase3 genes.
CONCLUSIONS: Overall, BIO-ZnNPs inclusion at 60 mg/kg feed showed the most advantage in different scenarios, compared to BIO-ZnNPs at 30 mg/kg feed. The positive effects on growth and intestinal health suggest that BIO-ZnNPs supplementation of aquafeeds has many benefits for farmed fish.

The joint impact of tadalafil (Cilais) as a pharmaceutical residue and microplastics on fish is not well comprehended. The current study examined haematological, biochemical, and antioxidant parameters, along with immunohistochemical and histological indications in tilapia (Oreochromis niloticus) after being exposed to tadalafil, polyethylene microplastics (PE-MPs), and their mixtures for 15 days. The fish were distributed into 1st group control group (The fish was maintained in untreated water without any supplements); 2nd group exposed to 10 mg/L PE-MPs;3rd group exposed to 20 mg/l tadalafil (Cilais); 4th group exposed to 20 mg/l tadalafil (Cilais) + 10 mg/LPE-MPs (in triplicate). The levels of creatinine, uric acid, glucose, AST, ALT, and albumin in fish treated with tadalafil alone or in combination with PE-MPs were significantly higher than those in the control group. Fish exposed to PE-MPs, tadalafil, and tadalafil plus PE-MPs showed significantly lower levels of RBCs, Hb, Ht, neutrophils, and lymphocytes compared to the control group. Serum levels of total antioxidant capacity and reduced glutathione (GSH) were notably lowered in fish groups subjected to PE-MPs, tadalafil, and tadalafil + PE-MPs combinations in comparison to the control group. Malondialdehyde (MDA) serum levels were notably elevated in fish groups subjected to PE-MPs, tadalafil, and tadalafil + PE-MPs combinations compared to the control group. The most severe impact was observed in the tadalafil + PE-MPs combination group. Interleukin-6 (IL-6) levels were significantly increased in liver tissues following exposure to both tadalafil and microplastics compared to tissues exposed to only one substance or the control group. Changes in the gills, liver, and renal tissues were seen following exposure to PE-MPs, tadalafil, and tadalafil + PE-MPs combination in comparison to the control group of fish. Ultimately, the mixture of tadalafil and PE-MPs resulted in the most detrimental outcomes. Tadalafil and PE-MPs exhibited showed greater adverse effects, likely due to tadalafil being absorbed onto PE-MPs.

Myxozoa, a unique group of obligate endoparasites within the phylum Cnidaria, can cause emerging diseases in wild and cultured fish populations. Recently, the myxozoan Myxobolus bejeranoi has been identified as a prevalent pathogen infecting the gills of cultured hybrid tilapia, leading to systemic immune suppression and considerable mortality. Here, we employed a proteomic approach to examine the impact of M. bejeranoi infection on fish gills, focusing on the structure of the granulomata, or cyst, formed around the proliferating parasite to prevent its spread to surrounding tissue. Enrichment analysis showed increased immune response and oxidative stress in infected gill tissue, most markedly in the cyst\'s wall. The intense immune reaction included a consortium of endopeptidase inhibitors, potentially combating the myxozoan arsenal of secreted proteases. Analysis of the cyst\'s proteome and histology staining indicated that keratin intermediate filaments contribute to its structural rigidity. Moreover, we uncovered skin-specific proteins, including a grainyhead-like transcription factor and a teleost-specific S100 calcium-binding protein that may play a role in epithelial morphogenesis and cysts formation. These findings deepen our understanding of the proteomic elements that grant the cyst its distinctive nature at the critical interface between the fish host and myxozoan parasite.

Regarding several infectious diseases in fish, multiple vaccinations are not favorable. The chimeric multiepitope vaccine (CMEV) harboring several antigens for multi-disease prevention would enhance vaccine efficiency in terms of multiple disease prevention. Herein, the immunogens of tilapia\'s seven pathogens including E. tarda, F. columnare, F. noatunensis, S. iniae, S. agalactiae, A. hydrophila, and TiLV were used for CMEV design. After shuffling and annotating the B-cell epitopes, 5,040 CMEV primary protein structures were obtained. Secondary and tertiary protein structures were predicted by AlphaFold2 creating 25,200 CMEV. Proper amino acid alignment in the secondary structures was achieved by the Ramachandran plot. In silico determination of physiochemical and other properties including allergenicity, antigenicity, glycosylation, and conformational B-cell epitopes were determined. The selected CMEV (OSLM0467, OSLM2629, and OSLM4294) showed a predicted molecular weight (MW) of 70 kDa, with feasible sites of N- and O-glycosylation, and a number of potentially conformational B-cell epitope residues. Molecular docking, codon optimization, and in-silico cloning were tested to evaluate the possibility of protein expression. Those CMEVs will further elucidate in vitro and in vivo to evaluate the efficacy and specific immune response. This research will highlight the new era of vaccines designed based on in silico structural vaccine design.

Cichlid fishes of the genus Oreochromis (tilapia) are among the most important fish for inland capture fisheries and global aquaculture. Deliberate introductions of non-native species for fisheries improvement and accidental escapees from farms have resulted in admixture with indigenous species. Such hybridization may be detrimental to native biodiversity, potentially leading to genomic homogenization of populations and the loss of important genetic material associated with local adaptation. By contrast, introgression may fuel diversification when combined with ecological opportunity, by supplying novel genetic combinations. To date, the role of introgression in the evolutionary history of tilapia has not been explored. Here we studied both ancient and recent hybridization in tilapia, using whole genome resequencing of 575 individuals from 23 species. We focused on Tanzania, a natural hotspot of tilapia diversity, and a country where hybridization between exotic and native species in the natural environment has been previously reported. We reconstruct the first genome-scale phylogeny of the genus and reveal prevalent ancient gene flow across the Oreochromis phylogeny. This has likely resulted in the hybrid speciation of one species, O. chungruruensis. We identify multiple cases of recent hybridization between native and introduced species in the wild, linked to the use of non-native species in both capture fisheries improvement and aquaculture. This has potential implications for both conservation of wild populations and the development of the global tilapia aquaculture industry.

BACKGROUND: Histone post-translational modifications (PTMs) are epigenetic marks that can be induced by environmental stress and elicit heritable patterns of gene expression. To investigate this process in an ecological context, we characterized the influence of salinity stress on histone PTMs within the gills, kidney, and testes of Mozambique tilapia (Oreochromis mossambicus). A total of 221 histone PTMs were quantified in each tissue sample and compared between freshwater-adapted fish exposed to salinity treatments that varied in intensity and duration.
RESULTS: Four salinity-responsive histone PTMs were identified in this study. When freshwater-adapted fish were exposed to seawater for two hours, the relative abundance of H1K16ub significantly increased in the gills. Long-term salinity stress elicited changes in both the gills and testes. When freshwater-adapted fish were exposed to a pulse of severe salinity stress, where salinity gradually increased from freshwater to a maximum of 82.5 g/kg, the relative abundance of H1S1ac significantly decreased in the gills. Under the same conditions, the relative abundance of both H3K14ac and H3K18ub decreased significantly in the testes of Mozambique tilapia.
CONCLUSIONS: This study demonstrates that salinity stress can alter histone PTMs in the gills and gonads of Mozambique tilapia, which, respectively, signify a potential for histone PTMs to be involved in salinity acclimation and adaptation in euryhaline fishes. These results thereby add to a growing body of evidence that epigenetic mechanisms may be involved in such processes.

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.