Aspects Of Fish Physiology Research Articles

Qualitative Shotgun Proteomics Strategy for Protein Expression Profiling of Fish Otoliths

Despite decades of research on fish otoliths and their capacity to serve as biochronological recorders, much remains unknown about their protein composition, the mechanisms by which proteins are incorporated into the otolith matrix, or the potential for using otolith proteins to provide insight into aspects of fish life history. We examined the protein composition of Atlantic cod (Gadus morhua) otoliths using a state-of-the-art shotgun proteomics approach with liquid chromatography coupled to an electrospray ionization-orbitrap tandem mass spectrometer. In addition to previously known otolith matrix proteins, we discovered over 2000 proteins not previously identified in cod otoliths and more than 1500 proteins not previously identified in any fish otoliths. These included three novel proteins (Somatolactin, F-actin-capping protein subunit beta, Annexin) primarily involved in binding calcium ions and likely mediating crystal nucleation. However, most of the otolith proteins were not necessarily related to otolith formation but rather to other aspects of fish physiology. For example, we identified sex-related biomarkers for males (SPATA6 protein) and females (Vitellogenin-2-like protein). We highlight some noteworthy classes of proteins having diverse functions; however, the primary goal here is not to discuss each protein separately. The number and diverse roles of the proteins discovered in the otoliths suggest that proteomics could reveal critical life history information from archived otolith collections that could be invaluable for understanding aspects of fish biology and population ecology. This proof-of-concept methodology paper provides a novel methodology whereby otolith proteomics can be further explored.

The Combined Use of Copper Sulfate and Trichlorfon Exerts Stronger Toxicity on the Liver of Zebrafish

In aquaculture, copper sulphate and trichlorfon are commonly used as disinfectants and insecticide, sometimes in combination. However, improper use can result in biotoxicity and increased ecological risks. The liver plays a crucial role in detoxification, lipid metabolism, nutrient storage, and immune function in fish. Selecting the liver as the main target organ for research helps to gain an in-depth understanding of various aspects of fish physiology, health, and adaptability. In the present study, zebrafish were exposed to Cu (0.5 mg/L) and Tri (0.5 mg/L) alone and in combination for 21 days. The results demonstrate that both Cu and Tri caused hepatocyte structure damage in zebrafish after 21 days of exposure, with the combination showing an even greater toxicity. Additionally, the antioxidant and immune enzyme activities in zebrafish liver were significantly induced on both day 7 and day 21. A transcriptome analysis revealed that Cu and Tri, alone and in combination, impacted various physiological activities differently, including metabolism, growth, and immunity. Overall, Cu and Tri, either individually or in combination, can induce tissue damage by generating oxidative stress in the body, and the longer the exposure duration, the stronger the toxic effects. Moreover, the combined exposure to Cu and Tri exhibits enhanced toxicity. This study provides a theoretical foundation for the combined use of heavy metal disinfectants and other drugs.

The Synergistic Effects of Combined Use of Mentha longifolia, Thymus carmanicus, and Trachyspermum copticum on Growth Performance, Feed Utilization, and Expression of Key Immune Genes in Rainbow Trout (Oncorhynchus mykiss).

Medicinal plants exhibit remarkable positive effects on different aspects of fish physiology. This study aimed to evaluate the possible impact of a combination of plants (Mentha longifolia, Thymus carmanicus, and Trachyspermum copticum) on growth performance, immune responses and key immune gene expression of rainbow trout. For this purpose, four diets were designed, including zero, 0.25, 0.5, and 1% of a mixture of plants per kg of diet, representing dietary treatments of control, T1, T2, and T3, respectively. Two hundred forty fish (weighing 23.11 ± 0.57 g) were fed 3% of body weight twice a day for 45 days. The results showed that growth parameters of weight gain (except for T1) and FCR were significantly improved in fish receiving all levels of plants, with T3 showing the best growth results. Digestive enzymes activities were notably increased in T1 and T2 compared to the control. Stress biomarkers (glucose and cortisol) were significantly decreased in T1 and T2, while T3 was not significantly different from the control. Immunological responses were significantly improved in T2, while T1 andT3 did not show a statistical difference in terms of lysozyme activity. Catalase activity was noticeably decreased in T1, although superoxide dismutase and malondialdehyde were highest in T2. Immune-related genes were significantly up-regulated in T3 compared to other treatments. Also, antioxidant enzyme coding genes were strongly up-regulated in T2 and T3. Overall, the present results suggest that 1% inclusion of the mixture of M. longifolia, T. carmanicus, and T. copticum (T2) can be used to improve the growth and immunity of rainbow trout.

Nutrigenomics and fish

Abstract The interaction of nutrients, environment, and genome determines the general physiological functioning and health of an organism. The branch of science which aims to understand these interactions is known as “Nutrigenomics.” Aquaculture and fisheries are the fast-growing food production systems and have an important role to play in achieving food and nutritional security. However, like other food production sectors, it also faces numerous challenges. Understanding the nutritional requirements and need-based dietary manipulation are perhaps the most effective and sustainable way of dealing with these challenges. In this review, we discuss the concept of nutrigenomics as a subset of multi-omics technology and highlight some studies encompassing nutrigenomics studies, with a specific focus on its application in fish nutrition. How these emerging techniques are applied in understanding various aspects of fish physiology as influenced by nutrition including nutritional supplements and various environmental factors like habitat, stress (temperature), and environmental contaminants have also been discussed.

Do environmental conditions (temperature and food composition) affect otolith shape during fish early-juvenile phase? An experimental approach applied to European Seabass (Dicentrarchus labrax)

Otolith shape is an efficient tool for fish stock discrimination. Therefore, it is crucial to identify the environmental parameters that could influence otolith morphogenesis and growth. Current global ocean warming negatively affects the production of polyunsaturated fatty acids (EPA and DHA) by phytoplankton and thus their availability in marine food webs. As EPA and DHA are essential nutrients for most fish species, their deficiency could affect many aspects of fish physiology, notably otolith morphogenesis. The goal of this study was to assess experimentally the combined influences of temperature (T) and dietary polyunsaturated fatty acid (PUFA) content on European seabass (Dicentrarchus labrax) otolith morphogenesis during early life stages. 300 individuals were reared from 94 to 200 days post hatch (dph) at 15 or 20 °C and fed a high (1.65% PUFA) or low (0.73% PUFA) nutrient diet. To analyze the temperature effect, Growing Degree Days (GDD) were used. Otolith morphometric measurements, shape factors and normalized Elliptical Fourier coefficients describing outline shape were extracted using image analysis. The directional asymmetry (DA) between left and right otolith shapes was not significantly correlated to the GDD or food nutrient level. The effects of T and PUFA on otolith shape were estimated using four linear mixed effects models and, for all descriptors of otolith outline, the best model included GDD, PUFA and T and their interaction as predictors. This temperature effect was described by GDD value and the interaction between GDD and T. Consequently, temperature has an effect on the speed but also on the morphogenesis trajectory of the otolith. Conversely, the concentration of PUFA in the diet had no significant effect on otolith shape. The otolith shape was first modified by a decrease in the width/length ratio during the first period of experiment and by the distance between rostrum and antirostrum during the second period of experiment. Our results indicate that otolith shape is very sensitive to environmental temperature and, as such, can be an effective tool for identifying fish stocks that have experienced different temperature regimes.

Expression and activity of lipid and oxidative metabolism enzymes following elevated temperature exposure and thyroid hormone manipulation in juvenile lake whitefish (Coregonus clupeaformis)

Temperature has unequivocal effects on several aspects of fish physiology, but the full extent of its interaction with key endocrine signaling systems to influence metabolic function remains unknown. The aim of the current study was to assess the individual and combined effects of elevated temperature and hyperthyroidism on hepatic metabolism in juvenile lake whitefish by quantifying mRNA abundance and activity of key metabolic enzymes. Fish were exposed to 13 (control), 17 or 21 °C for 0, 4, 8 or 24 days in the presence or absence of low-T4 (1 µg × g body weight−1) or high-T4 (10 µg × g body weight−1) treatment. Our results demonstrate moderate sensitivity to elevated temperature in this species, characterized by short-term changes in mRNA abundance of several metabolic enzymes and long-term declines in citrate synthase (CS) and cytochrome c oxidase (COX) activities. T4-induced hyperthyroidism also had several short-term effects on mRNA abundance of metabolic transcripts, including depressions in acetyl-coA carboxylase β (accβ) and carnitine palmitoyltransferase 1β (cpt1β), and stabilization of cs mRNA levels; however, these effects were primarily limited to elevated temperature groups, indicating temperature-dependent effects of exogenous T4 treatment in this species. In contrast, maximal CS and COX activities were not altered by hyperthyroidism at any temperature. Collectively, our data suggest that temperature has the potential to manipulate thyroid hormone physiology in juvenile lake whitefish and, under warm-conditions, hyperthyroidism may suppress certain elements of the β-oxidation pathway without substantial impacts on overall cellular oxidative capacity.

Discrimination of juvenile snapper (Chrysophrys auratus) growth and nutrition via metabolomic GC-MS methods

Many fish species utilise nursery habitats to enhance survival and growth through vulnerable juvenile life stages. Nursery habitats, however, are often threatened by a variety of stressors, and it is likely that some nursery habitats or locations are more degraded than others. If degraded nursery habitats impact juvenile fish growth or other aspects of fish physiology, a tool to detect this would have great utility in prioritising habitat conservation efforts. We assessed the ability of metabolic profiling to discriminate hatchery reared snapper (Chrysophrys auratus) that had differing food availability and growth rates. Metabolomic profiles of snapper from the different sample groups (i.e. different combinations of fast or slow growth rate and high and low food availability) had high levels of discrimination. This difference was largely driven by an unknown metabolite, which we suspect is a dipeptide proline compound. It is unclear if this unknown metabolite was specific to the results of the present study, or may have more generic value as a bio-indicator of nursery habitat quality. The next step is to analyse the metabolomic profiles of juvenile snapper from a gradient of locations with low to high nursery habitat quality and assess the ability of metabolomic methods to discriminate individual fish from across this more realistic setting.

Arginine Vasotocin Treatment Induces a Stress Response and Exerts a Potent Anorexigenic Effect in Rainbow Trout, Oncorhynchus mykiss

The peptide arginine vasotocin (AVT), homologous to mammalian arginine vasopressin, is involved in many aspects of fish physiology, such as osmoregulation, regulation of biological rhythms, reproduction, metabolism or responses to stress, and the modulation of social behaviours. Because a decrease in appetite is a general response to stress in fish and other vertebrates, we investigated the role of AVT as a possible food intake regulator in fish. We used i.c.v. injections for central administration of AVT to rainbow trout (Oncorhynchus mykiss). In a first experiment, we evaluated the temporal response of food intake after AVT treatment. In a second experiment, we investigated the effects of central AVT administration on the response of typical stress markers (plasma cortisol, glucose and lactate), as well as brain serotonergic, noradrenergic and dopaminergic activity. In addition, the mRNA levels of genes involved in food intake regulation [neuropetide Y, pro-opiomelanocortin (POMC), cocaine- and amphetamine-regulated transcript (CART) and corticotrophin-releasing factor (CRF)] and in CRF- (CRF-binding protein) and AVT-signalling (pro-VT and AVT receptor), were also assessed after AVT treatment. Our results showed that AVT is a potent anorexigenic factor in fish. Increases of plasma cortisol and glucose after AVT treatment strongly suggest that AVT administration induced a stress response and that AVT action was mediated by hypothalamic-pituitary-interrenal axis activation, which was also supported by the increase of the serotonergic activity in trout telencephalon and hypothalamus. The increased hypothalamic levels of POMC and CART suggest that these peptides might have a role in the anorexigenic action of AVT, whereas the involvement of CRF signalling is unclear.

Effects of colored light and tank color on growth indices and some physiological parameters of juvenile beluga (Huso huso)

International SturgeonResearch Institute, Guilan, IranSummaryThe influence of colored light and tank color was investigatedon growth performance (body weight, growth rate, carcasscomposition, etc.) and physiological status (blood and plasmaparameters) of beluga (Huso huso) juveniles. The study wasconducted using 64 specimens for colored light treatments withinitial weight 98.83 ± 1.42 (mean ± SE) g which were rearedunder white, red, green and blue light and using 80 specimensfor tank color treatments with initial weight 98.50 ±1.24 (mean ± SE) g which were reared in white, red, green,black and blue tanks, all for 12 weeks. Red light had asignificantly negative impact on beluga growth performance(in contrast with blue light) accompanied with reduced livertotal lipids and plasma albumin and elevated plasma cortisol,glucose, cholesterol and triglyceride (in contrast with the othertreatments). No significant effects of tank color were detectedon growth performance. Nevertheless, most of growth param-eters suggested a positive impact of black tank. Althoughplasma glucose levels in white tank were significantly higherthan the other tank colors, no significant effects of tank colorwere detected for the other physiological parameters. There-fore, based on the obtained results, blue light by establishingcomfort in beluga juveniles spelled increased growth perfor-mance and had positive significant effect on physiologicalconditions. Moreover, taking into consideration the consis-tency of all growth parameters among beluga juveniles rearedin black tanks, it is suggested that considerable results inregard to this treatment may be achieved if the rearing periodprolongs.IntroductionThe living fossil status of the lineage and the unusualmorphologic traits of sturgeons make the research on themscientifically valuable (Gardiner, 1984; Bemis et al., 1997).Caspian Sea is the habitat for the four commercial species ofsturgeon (Khodorevskaya et al., 1997) where their populationsare declining due to overfishing for meat and caviar produc-tion, habitat destruction, and environmental pollution (Billardand Lecointre, 2001). The beluga, Huso huso, is an importantcommercial species in the Caspian Sea and a good candidatefor aquaculture because of their fast growth, market price,propagation in captivity and high marketable value of theircaviar. In order to optimize the cultivation of this species,realizing its behavior and performance in culture conditions issubstantial. Among environmental factors that may influencefish performance in culture are colored light and tank color(Barton, 2002). The effects of colored light on disparate aspectsof fish physiology have been investigated such as growth,survival, neuro-hormonal system, reproduction, behavior andstress response (Head and Malison, 2000; Ruchin, 2001, 2004;Volpato and Barreto, 2001; Bayarri et al., 2002; Naor et al.,2003; Boulcott et al., 2005; Marchesan et al., 2005; Karak-atsouli et al., 2007, 2008). Each of the above studies has beenindicated that various light colors have relieved the physio-logical processes in different species. Hence, it is likely that thisspecies-specific quality relates to consistencies of fish visualstructure with its particular natural habitat traits. The effectsof tank color on different aspects of fish physiology have alsobeen investigated including growth performance, survival, skincolor and stress response (Papoutsoglou et al., 2000, 2005;Tamazouzt et al., 2000; Rotllant et al., 2003; Van der Salmet al., 2004; Jentoft et al., 2006; Strand et al., 2007). Thesestudies have indicated that reactions to tank color may varyaccording to fish species and life stage (Papoutsoglou et al.,2005). While light is easily adjusted in intensive indoor fishcultivation and it is possible to have tanks manufactured inany color, determining suitable light and tank color forfarming beluga is important for optimizing its production andcomfort. The present study aimed to investigate whethercolored light and tank color could affect beluga growthperformance and physiological status (blood and plasmaparameters). For this reason, fish were reared separately underwhite, red, green and blue light and in white, red, green, blackand blue tanks.Materials and methods

Quantification of whole brain arginine vasotocin for two Syngnathus pipefishes: elevated concentrations correlated with paternal brooding

Arginine vasotocin (AVT) regulates many aspects of fish physiology and behavior including courtship and reproduction. This study begins to address whether paternal functions for AVT have independently evolved in species in which paternal behavior has evolved. We quantified AVT in the brains of Syngnathus fuscus and Syngnathus floridae which, like other pipefishes and seahorses of the family Syngnathidae, brood embryos within specialized structures of the male. For both species, we measured AVT concentrations seventeenfold higher for some males during brooding compared to post-brooding males. Comparable whole brain AVT concentrations between gravid females and males with broods at some embryonic development stages suggest physiological similarities that we hypothesize is related to nutrient provisioning but should be elucidated with further studies including a detailed anatomical analysis of AVT production. Earlier studies have identified differences in the brooding structures of these species. Here we documented interspecific differences in the variability and mean AVT concentration for non-brooding males, the brood stage showing a return to post-brooding concentrations, and the variability of AVT concentrations for brooding males with embryos in some development stages. Future investigations should use these data to investigate the potential for divergent AVT function between species, sexes, and brooding males with embryos of different developmental stages.

Effect of music stimulus on gilthead seabream Sparus aurata physiology under different light intensity in a re‐circulating water system

The aim of the present study was to evaluate music effects (Mozart, K525) on gilthead seabream Sparus aurata and investigate whether its response to music was differentiated when combined with different lighting conditions. Therefore, S. aurata (mean ±s.e. 1·51 ± 0·01 g) were reared in re‐circulating water system under 80 and 200 lx and subjected to 2 and 4 h of music transmissions or to no music at all (control, ambient noise only). Underwater ambient noise of the equipment (e.g. pumps and aerators) in all experimental tanks was 121 dB re 1 μPa and music transmitted was set at 140 dB re 1 μPa. During the first 89 days of rearing, music resulted in enhanced growth. Nevertheless, at the end of the experiment (on day 117) no significant differences were found for body mass but music treatment resulted in more homogeneous fish populations than controls. Brain neurotransmitter levels were reduced especially when music transmission was combined with 200 lx. Feed utilization was significantly improved when fish were subjected to 4 h of music and 200 lx, while stomach proteolytic enzymes and intestine total carbohydrases were lower and higher, respectively, compared to controls. Some differences were also observed in liver and plasma fatty acids composition. The present results provide the initial evidence that music transmission under specific rearing conditions could have enhancing effects on S. aurata growth performance, at least at specific fish sizes. Moreover, the observed music effects on several aspects of fish physiology (e.g. digestive enzymes, fatty acid composition and brain neurotransmitters) imply that music could possibly provide even further enhancement in growth, quality, welfare and production.

Structural and phylogenetic comparison of three pepsinogens from Pacific bluefin tuna: Molecular evolution of fish pepsinogens

The amino acid sequences of three pepsinogens (PG1, PG2 and PG3) of Pacific bluefin tuna (Thunnus orientalis) were deduced by cloning and nucleotide sequencing of the corresponding cDNAs. The amino acid sequences of the pre-forms of PG1, PG2 and PG3 were composed of a signal peptide (16 residues each), a propeptide (41, 37 and 35 residues, respectively) and a pepsin moiety (321, 323 and 332 residues, respectively). Amino acid sequence comparison and phylogenetic analysis indicated that PG1 and PG2 belong to the pepsinogen A family and PG3 to the pepsinogen C family. Homology modeling of the three-dimensional structure suggested that the remarkably high specific activity of PG2 toward hemoglobin, which had been found previously, was partly due to a characteristic deletion of several residues in the S1'-loop region that widens the space of the active site cleft region so as to accommodate protein and larger polypeptide substrates more efficiently. Including the tuna and all other fish pepsinogen sequences available to date, the molecular phylogenetic comparison was made with reference to evolution of fish pepsinogens. It was suggested that functional divergences of pepsinogens (pepsins) occurring in fishes as well as in mammals, correlated with differences in various aspects of fish physiology.

Physiological Insights Towards Improving Fish Culture

The Triennial Aquaculture Meeting ‘‘Aquaculture 2007,’’ one of the largest aquaculture meetings in the world, cosponsored by the World Aquaculture Society, National Shellfish Association, and American Fisheries Society (AFS) Fish Culture Section, was held February 26 through March 2, 2007, in San Antonio, Texas. At this meeting, the AFS Fish Culture and Fish Physiology Sections co-organized a symposium entitled ‘‘Physiological Insights Towards Improving Fish Culture.’’ The symposium goals included providing a forum that would allow fish physiologists and aquaculturists to exchange scientific ideas, establish research collaborations, and work to improve finfish production using recent developments in basic and applied research. The symposium focused on four primary aspects of fish physiology and aquaculture: growth, reproduction, stress and immunology, and analgesia and anesthesia. Fifty presentations covered a diversity of species reared in a variety of production systems. The symposium was very well attended and was widely considered a success, as evidenced in part by the collection of articles published in this issue of the North American Journal of Aquaculture. It is clear that physiologists and aquaculturists working together can solve many of the key problems currently constraining the sustainable growth of world aquaculture. We wish to thank the symposium sponsors (Yellow Springs Instruments, Inc., and Aquatic Eco-Systems), the AFS Fish Culture and Fish Physiology Sections, and all of the scientists who participated in this inaugural symposium. The AFS Fish Culture and Fish Physiology Sections intend to host this symposium at all future Triennial Aquaculture Meetings, and we invite you to join us in San Diego in 2010.

Microarray Studies of Gene Expression in Fish

The use of microarrays for the study of various aspects of fish physiology has seen a spectacular increase in recent years. From early studies with model species, such as zebrafish, to current studies with commercially important species, such as salmonids, catfish, carp, and flatfish, microarray technology has emerged as a key tool for understanding developmental processes as well as basic physiology. In addition, microarrays are being applied to the fields of ecotoxicology and nutrigenomics. A number of different platforms are now available, ranging from microarrays containing cDNA amplicons to oligomers of various sizes. High-density microarrays containing hundreds of thousands of distinct oligomers have been developed for zebrafish and catfish. As this exciting technology advances, so will our understanding of global gene expression in fish. Furthermore, lessons learned from this experimentally tractable group of organisms can also be applied to more advanced organisms such as humans.

Endocrine Toxicants and Reproductive Success in Fish

There is compelling evidence on a global scale for compromised growth and reproduction, altered development, and abnormal behaviour in feral fish that can be correlated or in some cases causally linked with exposure to endocrine disrupting chemicals (EDCs). Attributing cause and effect relationships for EDCs is a specific challenge for studies with feral fish as many factors including food availability, disease, competition and loss of habitat also affect reproduction and development. Even in cases where there are physiological responses of fish exposed to EDCs (e.g., changes in reproductive hormone titres, vitellogenin levels), the utility of these measures in extrapolating to whole animal reproductive or developmental outcomes is often limited. Although fish differ from other vertebrates in certain aspects of their endocrinology, there is little evidence that fish are more sensitive to the effects of EDCs. Therefore, to address why endocrine disruption seems so widespread in fish, it is necessary to consider aspects of fish physiology and their environment that may increase their exposure to EDCs. Dependence on aquatic respiration, strategies for iono-osmotic regulation, and maternal transfer of contaminants to eggs creates additional avenues by which fish are exposed to EDCs. This paper provides an overview of responses observed in feral fish populations that have been attributed to EDCs and illustrates many of the factors that need consideration in evaluating the risks posed by these chemicals.

Dietary Protein Requirements of Fishes — A Reassessment

It is widely believed that fishes require more dietary protein than other vertebrates. Many aspects of fish physiology, nutrition, and trophic ecology have been interpreted within the context of this high protein requirement. Here, fishes are compared with terrestrial homeotherms in terms of (1) protein requirement for maintenance, (2) relative protein concentration in the diet required for maximum growth rate, (3) protein intake rate required for maximum growth rate, (4) efficiency of protein retention in growth, and (5) weight of growth achieved per weight of protein ingested. The two animal groups compared differ only in relative protein concentration in the diet required for maximum growth rate. This difference is explained in terms of homeotherms' greater requirement for energy and does not reflect absolute differences in protein requirement. The remaining measures of protein requirement suggest that fishes and terrestrial homeotherms are remarkably similar in their use of protein as a nutritional resource. Reinterpretation of the role of protein in fish physiology, nutrition, and trophic ecology is perhaps in order.