Figure - available from: Evolutionary Applications
This content is subject to copyright. Terms and conditions apply.
Relationship between aggression intensity (no. of agonistic interactions) and gene expression (DESeq2 normalized counts) in the six most aggressive fish at each density. Shown are examples of six responsive genes (out of 19) where there were significant interactions between aggression intensity and rearing density (q < 0.05; Table 1), suggesting that agonistic behaviour is regulated in a density‐dependent manner: (a) v‐fos FBJ murine osteosarcoma viral oncogene homolog Ab (fosab), (b) proopiomelanocortin a (pomca), (c) krt5, (d) nnt, (e) irg1 and (f) bag6l
Source publication
To meet future global demand for fish protein, more fish will need to be farmed using fewer resources, and this will require the selection of non‐aggressive individuals that perform well at high densities. Yet, the genetic changes underlying loss of aggression and adaptation to crowding during aquaculture intensification are largely unknown. We exa...
Citations
... Present study noted high expression of SST-I gene in both low as well high stocking density treatments. This aligns with previous findings indicating that sst1 was upregulated in tilapia at high density [61] as well as in cichlids [62,63]. After the dietary supplementation of curcumin in current study at high density the expression of SST-1 drops which indicates the stimulatory effect in terms of growth. ...
... Increase in the chemical composition against curcumin supplementation has also been previously observed in Nile tilapia [64]. Present study aligns with previous findings indicating that SST-I was upregulated in tilapia at high density [61] as well as in cichlids [62,65]. This increase in the growth parameters and crude protein is due to digestive enhancer properties of curcumin [66,67]. ...
... Addition of curcumin in diet significantly influences the expression of appetite-regulating neuropeptides like POMC in tilapia [94]. The present study aligns with previous findings conducted on tilapia [61]. ...
The present study evaluated the effects of curcumin on growth, immune and antioxidant response in tilapia (Oreochromis niloticus). An optimum dose of curcumin was investigated by feeding four different levels of this compound in combination with three different regimes of stocking density (12 treatments). Fish were reared at three densities; low density (LD = 1.50 kg/m³), medium density (MD = 3.00 kg/m³), and high density (HD = 4.50 kg/m³). Each treatment was fed with four different levels of dietary supplementation of curcumin (C0 = 0 mg/kg, C1 = 50 mg/kg, C2 = 100 mg/kg, and C3 = 150 mg/kg) for 60 days. Each treatment has three replicates (n = 50/replicate in LD, 100/replicate in MD, 150/ replicate in HD). Although better growth was observed in MD, however treatments at all densities fed with C1 diet showed improved growth as compared to other diets. Chemical composition of fish and activity of amylase, lipase and protease in all treatments were noted to be similar. Levels of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and cortisol in MD and HD treatments were similar to those in LD treatment. However, fish fed with C1 diet in each density treatment showed the lowest values of antioxidant enzymes. Similarly, the levels of malondialdehyde were noted to be similar in MD and HD treatments as compared to that in LD. Its levels were lower in fish fed with C1 and C3 diets in all density treatments. Expression of pro-opiomelanocortin-α (POMC-α), Somatostatins-1 (SST-1) and Interleukin 1-β (IL-1β) did not increase in MD and HD treatments in response to high stocking density when compared with LD treatment. The lowest levels of these genes were noted in fish fed with C2 and C3 diets in all treatments. In conclusion, supplementation of curcumin in diet of tilapia improved growth and antioxidant response in tilapia. optimum dose of curcumin for tilapia culture is 50 mg/kg at the density of 3.00 kg/m³which might be further investigated for intensive culture.
... The present study observed an equivalent expression of the SST-I gene in low and high stocking density treatments although the difference in their stocking densities. This observation is consistent with previous research showing upregulation of SST-1 in tilapia under high density conditions [45], as well as in cichlids [46,47]. Following the dietary supplementation of N-acetyl cysteine in the present study under high density conditions, the expression of SST-1 decreased, indicating a stimulatory effect on growth. ...
The study investigated the impact of N-acetyl cysteine on growth, immune response, and antioxidant activity in tilapia (Oreochromis niloticus). Fish were reared at three densities (1.50, 3.00, and 4.50 kg/m³) with four levels of N-acetyl cysteine supplementation (0, 2, 4, and 6 mg/kg) over 60 days. Better growth was observed at low density, but at all densities, fish fed the highest N-acetyl cysteine level (6 mg/kg) showed improved growth. Chemical composition of fish and activity of amylase, lipase and protease in all treatments were noted to be insignificant. The levels of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and cortisol in HD treatments were high as compared to LD and MD treatment. However, fish fed with N3 diet in each density treatment showed the lowest level of antioxidant enzymes as well as cortisol. Similarly, the levels of malondialdehyde were noted to be high at HD treatments as compared to that in LD and MD. Its levels were lower in fish fed with N3 diets in all density treatments. Expression of somatostatins-1 did not increase in MD and HD treatments in response to high stocking density when compared with LD treatment. However, pro-opiomelanocortin-α level was reduced after N3 diet in HD treatment and interleukin 1-β expression increased after N3 supplement in HD treatment. In conclusion, N-acetyl cysteine supplementation improved growth and antioxidant response in tilapia. The most optimum dose of N-acetyl cysteine was noted to be 6 mg/kg at high stocking, suggesting the potential role of this nutraceutical in tilapia intensive culture.
... High-throughput transcriptomic studies with different fish species have mainly focused on the immunological responses to pathogens and parasites [11], and on the effects of alkalinity [12], rearing density [13,14], temperature [15][16][17][18], salinity [19], ammonia [20], and fasting [21,22]. However, studies on the transcriptional effects of other aquaculture stressors are still lacking. ...
Gilthead seabream (Sparus aurata) is an important species in Mediterranean aquaculture. Rapid intensification of its production and sub-optimal husbandry practices can cause stress, impairing overall fish performance and raising issues related to sustainability, animal welfare, and food safety. The advent of next-generation sequencing technologies has greatly revolutionized the study of fish stress biology, allowing a deeper understanding of the molecular stress responses. Here, we characterized for the first time, using RNA-seq, the different hepatic transcriptome responses of gilthead seabream to common aquaculture challenges, namely overcrowding, net handling, and hypoxia, further integrating them with the liver proteome and metabolome responses. After reference-guided transcriptome assembly, annotation, and differential gene expression analysis, 7, 343, and 654 genes were differentially expressed (adjusted p-value < 0.01, log2|fold-change| >1) in the fish from the overcrowding, net handling, and hypoxia challenged groups, respectively. Gene set enrichment analysis (FDR < 0.05) suggested a scenario of challenge-specific responses, that is, net handling induced ribosomal assembly stress, whereas hypoxia induced DNA replication stress in gilthead seabream hepatocytes, consistent with proteomics and metabolomics’ results. However, both responses converged upon the downregulation of insulin growth factor signalling and induction of endoplasmic reticulum stress. These results demonstrate the high phenotypic plasticity of this species and its differential responses to distinct challenging environments at the transcriptomic level. Furthermore, it provides significant resources for characterizing and identifying potentially novel genes that are important for gilthead seabream resilience and aquaculture production efficiency with regard to fish welfare.
... According to recent FAO data (18), Nile tilapia, Oreochromis niloticus, is currently amongst the three most farmed fish species globally, with China, Indonesia, Egypt, Bangladesh, and Brazil emerging as the largest producers (19). Aquaculture sectors have been under pressure to produce more with fewer resourcesincreasing production using less feed, water, and space to meet the growing global demand for fish proteins (20). However, this pressure tends to affect the environment and the welfare of farmed fish (21). ...
The primary aim of this study was to comprehensively evaluate the welfare of Nile tilapia (Oreochromis niloticus) throughout their entire life cycle within aquaculture, spanning from reproduction to slaughter. The methodology was structured to identify welfare indicators closely aligned with the principles of animal freedoms defined by the Farm Animal Council, encompassing environmental, health, nutritional, behavioral, and psychological freedom. Notably, psychological freedom was inherently considered within the behavioral and physical analyses of the animals. To accomplish this, an integrative systematic literature review was conducted to define precise indicators and their corresponding reference values for each stage of tilapia cultivation. These reference values were subsequently categorized using a scoring system that assessed the deviation of each indicator from established ideal (score 1), tolerable (score 2), and critical (score 3) ranges for the welfare of the target species. Subsequently, a laboratory experiment was executed to validate the pre-selected health indicators, specifically tailored for the early life stages of tilapia. This test facilitated an assessment of the applicability of these indicators under operational conditions. Building on the insights gained from this experimentation, partial welfare indices (PWIs) were computed for each assessed freedom, culminating in the derivation of a general welfare index (GWI). Mathematical equations were employed to calculate these indices, offering a quantitative and standardized measure of welfare. This approach equips tilapia farmers and processors with the tools necessary for the continuous monitoring and enhancement of their production systems and stimulate the adoption of more sustainable and ethical practices within the tilapia farming.
... Through the enrichment analysis of gene functions and pathways, the process of molecular changes in the organism in response to stress and the functional changes that may eventually develop can be determined [12]. Currently, transcriptome sequencing studies have been carried out for evaluating the effect of stocking density on many fish species, such as Nile tilapia (Oreochromis niloticus) [15], yellow croaker (Larimichthys crocea) [16], grass carp (Ctenopharyngodon idellus) [4,17], and rainbow trout (Oncorhynchus mykiss) [18]. These studies have revealed that gene regulation affects growth, metabolism, and immunity under high stocking densities, which laid the scientific and theoretical foundation for developing the production of these cultured species. ...
Long-term high stocking density often brings negative effects such as decreased body weight, decreased immunity, and increased mortality to cultured fish, while the effects of short-term stocking are relatively less studied. In this experiment, we characterized spatial and temporal gene expression in black porgy (Acanthopagrus schlegelii) liver by establishing two stocking density groups—high (H: 26.5 kg/m3) and low (L: 2.95 kg/m3)—and conducting transcriptome sequencing before collecting liver samples at two time points: 6 h (AL and AH) and 60 d (CL and CH) into the culture trial. There were 648 and 550 differentially expressed genes (DEGs) in the AL-vs-AH and CL-vs-CH groups, respectively. The DEGs in the AL-vs-AH group were significantly enriched in steroid biosynthesis, terpenoid backbone biosynthesis, the PPAR signaling pathway, proteasome, aminoacyl-tRNA biosynthesis, and ribosome biogenesis in eukaryotes. The DEGs in the CL-vs-CH group were more significantly enriched in lipid metabolism-related pathways, such as the PPAR signaling pathway, fatty acid metabolism, and cholesterol metabolism. In addition, immune-related pathways such as the phagosome and complement and coagulation cascades were also enriched in the CL-vs-CH group. The expression changes concerning the DEGs in each group were further analyzed. The DEGs related to steroid synthesis, protein synthesis, and the degradation pathways were down-regulated, but immune-related genes were generally up-regulated in the AH group. The DEGs related to lipid synthesis were significantly up-regulated in the CH group, but the DEGs related to lipid consumption and utilization were down-regulated. The expression of immune-related DEGs was also negatively affected in the CH group. These results suggest that acute and chronic crowding stress affects lipid metabolism and immune regulation in the liver of black porgy. Acute stress particularly affected hepatic protein metabolism, while chronic stress showed more effects on hepatic lipid metabolism. The results of this study provide a theoretical basis for understanding the effects of high stocking densities upon black porgy and may also provide a reference for crowding stress regulation studies in other fish species.
... High cortisol has also been shown to increase hepatic insulin-like growth factor 1 binding protein 1(igfbp) 1b1 and -1b2 [38,39]. Crowding in Nile tilapia has been shown to increase the expression of somatostatin-1 (sst1), V-fos FBJ murine osteosarcoma viral oncogene homolog Ab (fosab) and prolactin genes [21,40]. There is however considerable variation in how fish respond to a stressor because of genetic differences among different taxa and also within stocks and species [41]. ...
Chronic stress is a serious threat to aquaculture as it lowers fish growth performance and compromises fish welfare. The exact mechanism by which growth is retarded is, however, not clearly understood. This study sought to elucidate the gene expression profiles associated with chronic stress in cultured Nile tilapia (Oreochromis niloticus) reared for 70 days at different ammonia concentrations and stocking densities. Fish in the treatment groups showed negative growth, while the controls showed positive allometric growth. The specific condition factor (Kn) ranged from 1.17 for the controls to 0.93 for the ammonia and 0.91 for the stocking density treatments. RNA was extracted from muscle tissue using TRIzol followed by library construction and Illumina sequenc-ing. Comparative transcriptome analysis revealed 209 differentially expressed genes (DEGs) (156 up-and 53 down-regulated) in the ammonia and 252 DEGs (175 up-and 77 down-regulated) in the stocking density treatment. In both treatments, 24 and 17 common DEGs were up-and down-regulated , respectively. DEGs were significantly enriched in six pathways associated with muscle activity , energy mobilization and immunity. The heightened muscular activity consumes energy which would otherwise have been utilized for growth. These results bring to fore the molecular mechanisms underlying chronic stress' suppression of growth in cultured Nile tilapia.
... Such studies provide the background to show that trait convergence is often achieved through genetic changes to shared pathways, genes or even molecular sites, suggesting that estimate the degree of genetic convergence expected for specific types of convergent traits (Sackton and Clark, 2019). Therefore, gene expression patterns offer new opportunities to decipher the molecular mechanisms of complex behaviours affected by domestication (Rodríguez- Barreto et al., 2019). Transcriptomics provides the ideal platform to approaches will be most powerful when they are combined into integrative studies that link transcriptional variation with neural activity, physiology and genetic variation in order to revolutionize behavioural studies (Fischer et al., 2021) Recent studies carried out on mullet, Mugil cephalus, showed a clear activation of pathways through the differential expression of a large number inmune related genes to the immune system in the kidney and spleen after being challenged with the bacterium Lactococcus garvieae . ...
... This type of protocol allows us to evaluate the individual aggressive propensity as there are no wins or losses 93,94 ; therefore, no effect of social rank on the stress response 95,96 . Additionally, mirror-elicited aggression is a predictor of individual stress 70 and is associated with gene expression in the hypothalamus of critical genes involved in the stress response of Nile tilapia 71 . Furthermore, despite criticism addressed to this method, it was recently demonstrated that several cichlid species in their natural environments aggressively react to their mirror image, expressing resembling behavioral patterns presented during fights with co-specifics 66 . ...
Cannabidiol (CBD) is a substance derived from Cannabis sativa, widely studied in medicine for controlling neural diseases in humans. Besides the positive effects on humans, it also presents anxiolytic proprieties and decreases aggressiveness and stress in mammals. Therefore, CBD has the potential to increase welfare in reared animals, as it seems to reduce negative states commonly experienced in artificial environments. Here, we tested the effect of different CBD doses (0, 1, 10 and 20 mg/kg) on aggressiveness, stress and reproductive development of the Nile tilapia (Oreochromis niloticus) a fish reared worldwide for farming and research purposes. CBD mixed with fish food was offered to isolated fish for 5 weeks. The 10 mg/kg dose decreased fish’s aggressiveness over time, whereas 20 mg/kg attenuated non-social stress. Both doses decreased the baseline cortisol level of fish and increased the gonadosomatic index. However, CBD 1 and 10 mg/kg doses decreased the spermatozoa number. No CBD dose affected feeding ingestion and growth variables, showing that it is not harmful to meat production amount. Despite the effect on spermatozoa, CBD supplementation exhibits high potential to benefit animals’ lives in artificial environments. Therefore, we showed for the first time that CBD could be used as a tool to increase non-mammal welfare, presenting a great potential to be explored in other husbandry and captivity species.
... However, the intensification of aquaculture is associated with challenges regarding its sustainability, including impact on animal health and welfare, the environment, food safety and economic viability (Stentiford et al., 2017). Intensive aquaculture can expose fish to crowding, handling and social stressors, which can induce adverse effects on health and fitness, such as impaired growth, depressed immunity, and increased susceptibility to disease (Conte, 2004;Ellison et al., 2018;Rodriguez-Barreto et al., 2019). Increasing resistance to stress and disease is therefore a priority in order to improve the sustainability of aquaculture. ...
Farmed fish are commonly exposed to stress in intensive aquaculture systems, often leading to immune impairment and increased susceptibility to disease. As microbial communities associated with the gut and skin are vital to host health and disease resilience, disruption of microbiome integrity could contribute to the adverse consequences of stress exposure. Little is known about how stress affects the fish microbiome, especially during sensitive early life stages when initial colonisation and proliferation of host-associated microbial communities take place. Therefore, we compared the effects of two aquaculture-relevant early-life stressors on the gut and skin microbiome of Atlantic salmon fry (four months post hatching) using 16S rRNA amplicon sequencing. Acute cold stress applied during late embryogenesis had a pronounced, lasting effect on the structure of the skin microbiome, as well as a less consistent effect on the gut microbiome. Follow-up targeted qPCR assays suggested that this is likely due to disruption of the egg shell microbial communities at the initial stages of microbiome colonisation, with persistent effects on community structure. In contrast, chronic post hatching stress altered the structure of the gut microbiome, but not of the skin. Both types of stress promoted similar Gammaproteobacteria ASVs, particularly within the genera Acinetobacter and Aeromonas, which include several important opportunistic fish pathogens. Our results demonstrate the sensitivity of the salmon microbiome to environmental stressors during early life, with potential associated health impacts on the host. We also identified common signatures of stress in the salmon microbiome, which may represent useful microbial stress biomarkers.
... In contrast, some welfare indicators, like eye and body darkening, can be indicative of social stress in territorial or aggressive species like Nile tilapia (Champneys et al., 2018;Freitas et al., 2014) or Atlantic salmon (O'Connor et al., 1999;Suter and Huntingford, 2002), but may be totally unsuitable for shoaling fish. Other individual based indicators, such as plasma cortisol (Pavlidis et al., 2013), expression of stress-related genes (Rodriguez-Barreto et al., 2019;Uren Webster et al., 2018), or the presence of bacterial biomarkers (Uren Webster et al., 2020), require analytical equipment and training that are not typically available within an aquaculture setting; they are laboratory-based welfare indicators, not operational ones (Noble et al., 2018). ...
Lumpfish (Cyclopterus lumpus L.) are widely used for controlling sea lice in salmon farming, but their welfare is often challenged by poor husbandry, stress, and disease outbreaks, which compromise their ability to delouse salmon and cause public concern. It is hence important to identify when the welfare of lumpfish is being compromised in a simple and effective manner so that remedial actions can be taken. We developed, validated and tested a Lumpfish Operational Welfare Score Index (LOWSI) based on a visual assessment of skin and fin damage, eye condition, sucker deformities and relative weight, operational welfare indicators that fish farmers considered to be the most informative and were validated against cortisol measurements. We also present percentile length-weight charts to enable fish farmers to detect underweight and emaciated lumpfish at different stages of development. The lumpish welfare score index was quick and easy to score and was highly repeatable (intra class correlation coefficient = 0.83 ± 0.05). Most lumpfish (71%) displayed good welfare, but significant differences were found between six commercial sites and 28% of lumpfish had lower than normal weights for their length, and 10% were emaciated. The most common welfare problems were sucker deformities and fin damage in hatcheries, and poor eye condition and body damage in sea cages, conditions that may increase the risk of emaciation. Being able to score the welfare of lumpfish quickly and accurately will help improve their welfare, reduce stress-related mortalities, and improve the sustainability of the salmon farming industry.
