鱼类低温应激反应的调控机制

鱼类遭受低温胁迫易产生分子、细胞和组织损伤, 甚至导致个体死亡。鱼类机体细胞感受到低温刺激后, 通过多种应激通路将低温信号传递至细胞核, 启动低温应激反应, 建立新的胞内稳态, 从而增强抗寒能力。低温可激活鱼类内分泌系统释放皮质醇和甲状腺素等激素, 调控代谢、渗透压和免疫反应, 最终引起生理和行为变化。鱼类低温应激反应受表观遗传修饰、转录和翻译、前体RNA可变剪接和蛋白质翻译后修饰等多层级的复杂调控。目前, 采用多组学技术已经鉴定到大量与低温响应相关的效应基因和调控通路。研究表明, 能量代谢和抗氧化应激反应在鱼类抗寒能力的建成起着重要作用。其他环境因子(如低氧和盐度)及鱼体生理状态(如饥饿和营养)也影响鱼类对低温刺激的反应和抗寒能力。鉴定抗寒相关的分子标记并解析其关联基因的作用机制对鱼类的抗寒育种具有重要意义。     

Conservation physiology for applied management of marine fish: an overview with perspectives on the role and value of telemetry

Physiological studies focus on the responses of cells, tissues and individuals to stressors, usually in laboratory situations. Conservation and management, on the other hand, focus on populations. The field of conservation physiology addresses the question of how abiotic drivers of physiological responses at the level of the individual alter requirements for successful conservation and management of populations. To achieve this, impacts of physiological effects at the individual level need to be scaled to impacts on population dynamics, which requires consideration of ecology. Successfully realizing the potential of conservation physiology requires interdisciplinary studies incorporating physiology and ecology, and requires that a constructive dialogue develops between these traditionally disparate fields. To encourage this dialogue, we consider the increasingly explicit incorporation of physiology into ecological models applied to marine fish conservation and management. Conservation physiology is further challenged as the physiology of an individual revealed under laboratory conditions is unlikely to reflect realized responses to the complex variable stressors to which it is exposed in the wild. Telemetry technology offers the capability to record an animal's behaviour while simultaneously recording environmental variables to which it is exposed. We consider how the emerging insights from telemetry can strengthen the incorporation of physiology into ecology.     

运输过程中水质和鱼类生理指标的变化及运输控制策略

鱼类运输应激是世界范围内面临的重要问题, 标准化运输操作规程的制定有利于水产养殖业的健康发展。血浆皮质醇是经典的应激评价指标, 在运输过程中持续上升, 适用于鱼类短途和长途运输, 而血糖则更适用于鱼类短途运输。乳酸、CO₂、渗透压等生理指标也应更多的被应用于运输应激评价。水质恶化(尤其是pH降低和氨累积)和应激反应是鱼类运输中急需解决的关键问题, 而现有的解决措施并不完善。水质和生理指标是相互影响的, 相关研究中应联合分析两者对运输的影响。文章综合分析了运输对鱼类造成的应激反应、水质恶化以及常用的抗应激运输措施, 进而对后续研究进行展望, 旨在为相关的研究提供基础资料。     

Sound the alarm: A meta‐analysis on the effect of aquatic noise on fish behavior and physiology

The aquatic environment is increasingly bombarded by a wide variety of noise pollutants whose range and intensity are increasing with each passing decade. Yet, little is known about how aquatic noise affects marine communities. To determine the implications that changes to the soundscape may have on fishes, a meta‐analysis was conducted focusing on the ramifications of noise on fish behavior and physiology. Our meta‐analysis identified 42 studies that produced 2,354 data points, which in turn indicated that anthropogenic noise negatively affects fish behavior and physiology. The most predominate responses occurred within foraging ability, predation risk, and reproductive success. Additionally, anthropogenic noise was shown to increase the hearing thresholds and cortisol levels of numerous species while tones, biological, and environmental noise were most likely to affect complex movements and swimming abilities. These findings suggest that the majority of fish species are sensitive to changes in the aquatic soundscape, and depending on the noise source, species responses may have extreme and negative fitness consequences. As such, this global synthesis should serve as a warning of the potentially dire consequences facing marine ecosystems if alterations to aquatic soundscapes continue on their current trajectory.     

Tricaine methane‐sulfonate (MS‐222) application in fish anaesthesia

Tricaine methane‐sulfonate (MS‐222) is one of the most widely used anaesthetics for poikilotherms worldwide. This paper outlines its anaesthetic efficacy and dosage in fish and legislation for its use, fish stress responses to MS‐222 anaesthesia and its effect on fish physiology and blood properties, pharmacokinetics, genotoxicity, immune response, potential interference with fish hepatic cytochrome P450 spectra, and its impact on nerve sensitivity. Key questions arising from the available data are analysed, such as regulatory constraints on its use, the need for the standardization of buffering protocols, and interdependencies of the factors impacting the specific applicative efficacy of MS‐222. Current research has provided an abundance of data on MS‐222 use in fish, although the applications within these studies are often impractical at the farming level. Specific emphasis is therefore placed on highlighting application strategies on a practical basis, presenting potential future research on topics that require in‐depth analysis (preparation and storage of anaesthetic solutions, pre‐anaesthetic sedation and stress reduction, cortisol response in aquarium fish, toxicity of MS‐222 metabolites, and possible immunodepressive properties). Additionally, both from a scientific and practical perspective, it is necessary to have a better understanding of safety margins, induction, immersion and recovery times for many (marine and freshwater, farmed and ornamental) fish species in order to achieve optimal utilization.     

Plenty more fish in the sea: comparative and functional genomics using teleost models.

Biology has collaborated with evolution to create an enormous repertoire of animal variation. This in turn has provided experimental biologists with models that can be used in the lab to simulate more complex systems. Amongst the organisms that have been used in this way are fish, where a large number of species have been utilised in a variety of different ways. Fish possess the smallest genomes of any vertebrate, making them ideal as models for genome analysis and gene discovery. Fish are also easy to maintain in a laboratory environment and can be bred easily. Fish often have well-defined physiology and respond well to many experimental procedures. Finally, fish are of great economic importance in their own right, as one of the world's largest sources of protein. In this review, the relationship between fish species is examined along with the role of different fish models in a wide range of biological disciplines.     

Effect of dietary ascorbic acid on growth and non-specific immune responses of tiger puffer, Takifugu rubripes

We report nutritional physiology and non-specific immune responses of ascorbic acid (AA) in puffer fish for the first time. This study aimed to examine the essentiality and requirements of AA in diets for the tiger puffer, Takifugu rubripes based on growth performance, liver AA and bone collagen concentration, and non-specific immune responses. Five casein-gelatin based semi-purified diets were formulated to contain five graded levels of l-ascorbyl-2-monophosphate at 0, 40, 80, 160 and 700mg/kg (designated as AMP0, AMP40, AMP80, AMP160 and AMP700, respectively) and fed to triplicate groups of fish. After 10weeks of feeding trial, growth performances of fish (initial body weight, 35g) fed the AMP0 were significantly lower compared to that of fish fed diets supplemented with AMP. The fish fed the AMP0 diet also exhibited significantly lower hematocrit, condition factor and hepatosomatic index compared to the fish fed diets supplemented with AMP. Phagocytic activity (NBT assay) was significantly lower in fish fed the AMP0 diet than in fish fed the AMP containing diets. Plasma lysozyme activity of fish fed the AMP80 and AMP160 was significantly higher than that of fish fed the AMP0. Dietary supplementation of AMP significantly increased the liver superoxide dismutase in the fish. Myeloperoxidase activity of fish fed the AMP0 was significantly lower compared to that of fish fed the AMP containing diets. Bone collagen level tended to increase numerically and total AA concentration in liver of fish was significantly increased in a dose dependent manner by the supplementation of AMP. Therefore, tiger puffer requires exogenous ascorbic acid and the optimum dietary level could be 29mg AA/kg diet for normal growth and physiology. Dietary AA concentration over 82mg/kg could be required to enhance non-specific immune responses of the fish. However, it does not seem that the fish needs an overdose of dietary AA (>160mg/kg) for better non-specific immune responses.     

Biomimetic Sensors： Active Electrolocation of Weakly Electric Fish as a Model for Active Sensing in Technical Systems

Instead of vision, many nocturnal animals use alternative senses for navigation and object detection in their dark environment. For this purpose, weakly electric mormyrid fish employ active electrolocation, during which they discharge a specialized electric organ in their tail which discharges electrical pulses. Each discharge builds up an electrical field around the fish, which is sensed by cutaneous electroreceptor organs that are distributed over most of the body surface of the fish. Nearby objects distort this electrical field and cause a local alteration in current flow in those electroreceptors that are closest to the object. By constantly monitoring responses of its electroreceptor organs, a fish can detect, localize, and identify environmental objects.Inspired by the remarkable capabilities of weakly electric fish in detecting and recognizing objects, we designed technical sensor systems that can solve similar problems of remote object sensing. We applied the principles of active electrolocation to technical systems by building devices that produce electrical current pulses in a conducting medium (water or ionized gases) and simultaneously sense local current density. Depending on the specific task a sensor was designed for devices could (i) detect an object, (ii) localize it in space, (iii) determine its distance, and (iv) measure properties such as material properties, thickness, or material faults. Our systems proved to be relatively insensitive to environmental disturbances such as heat, pressure, or turbidity. They have a wide range of applications including material identification, quality control, non-contact distance measurements, medical applications and many more. Despite their astonishing capacities, our sensors still lag far behind what electric fish are able to achieve during active electrolocation. The understanding of the neural principles governing electric fish sensory physiology and the corresponding optimization of our sensors to solve certain technical tasks therefore remain ongoing goals of our research.     

Biomimetic Sensors: Active Electrolocation of Weakly Electric Fish as a Model for Active Sensing in Technical Systems

Instead of vision, many nocturnal animals use alternative senses for navigation and object detection in their dark environment. For this purpose, weakly electric mormyrid fish employ active electrolocation, during which they discharge a specialized electric organ in their tail which discharges electrical pulses. Each discharge builds up an electrical field around the fish, which is sensed by cutaneous electroreceptor organs that are distributed over most of the body surface of the fish. Nearby objects distort this electrical field and cause a local alteration in current flow in those electroreceptors that are closest to the object. By constantly monitoring responses of its electroreceptor organs, a fish can detect, localize, and identify environmental objects.Inspired by the remarkable capabilities of weakly electric fish in detecting and recognizing objects, we designed technical sensor systems that can solve similar problems of remote object sensing. We applied the principles of active electrolocation to technical systems by building devices that produce electrical current pulses in a conducting medium (water or ionized gases) and simultaneously sense local current density. Depending on the specific task a sensor was designed for devices could (i) detect an object, (ii) localize it in space, (iii) determine its distance, and (iv) measure properties such as material properties, thickness, or material faults. Our systems proved to be relatively insensitive to environmental disturbances such as heat, pressure, or turbidity. They have a wide range of applications including material identification, quality control, non-contact distance measurements, medical applications and many more. Despite their astonishing capacities, our sensors still lag far behind what electric fish are able to achieve during active electrolocation. The understanding of the neural principles governing electric fish sensory physiology and the corresponding optimization of our sensors to solve certain technical tasks therefore remain ongoing goals of our research.     

The challenges of implementing pathogen control strategies for fishes used in biomedical research

Over the past several decades, a number of fish species, including the zebrafish, medaka, and platyfish/swordtail, have become important models for human health and disease. Despite the increasing prevalence of these and other fish species in research, methods for health maintenance and the management of diseases in laboratory populations of these animals are underdeveloped. There is a growing realization that this trend must change, especially as the use of these species expands beyond developmental biology and more towards experimental applications where the presence of underlying disease may affect the physiology animals used in experiments and potentially compromise research results. Therefore, there is a critical need to develop, improve, and implement strategies for managing health and disease in aquatic research facilities. The purpose of this review is to report the proceedings of a workshop entitled "Animal Health and Disease Management in Research Animals" that was recently held at the 5th Aquatic Animal Models for Human Disease in September 2010 at Corvallis, Oregon to discuss the challenges involved with moving the field forward on this front.     

Paternal effects in a wild‐type zebrafish implicate a role of sperm‐derived small RNAs

While the importance of maternal effects has long been appreciated, a growing body of evidence now points to the paternal environment having an important influence on offspring phenotype. Indeed, research on rodent models suggests that paternal stress leaves an imprint on the behaviour and physiology of offspring via nongenetic information carried in the spermatozoa; however, fish have been understudied with regard to these sperm‐mediated effects. Here, we investigated whether the zebrafish was subjected to heritable influences of paternal stress by exposing males to stressors (conspecific‐derived alarm cue, chasing and bright light) before mating and assessing the behavioural and endocrine responses of their offspring, including their behavioural response to conspecific‐derived alarm cue. We found that after males are exposed to stress, their larval offspring show weakened responses to stressors. Small RNA sequencing subsequently revealed that the levels of several small noncoding RNAs, including microRNAs, PIWI‐interacting RNAs and tRNA‐derived small RNAs, were altered in the spermatozoa of stressed fathers, suggesting that stress‐induced alterations to the spermatozoal RNA landscape may contribute to shaping offspring phenotype. The work demonstrates that paternal stress should not be overlooked as a source of phenotypic variation and that spermatozoal small RNAs may be important intergenerational messengers in fish.     

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.     

Threat Sensitivity in Bicolor Damselfish: Effects of Sociality and Body Size

Threat sensitivity involves graded antipredator responses that reflect the degree of predatory threat encountered. Models of predatory Atlantic trumpetfish (Aulostomus maculatus) were presented to differently sized juvenile bicolor damselfish (Pomacentrus partitus) that occurred singly or in small groups to test for threat sensitivity. Bicolor damselfish displayed threat sensitivity by responding more strongly: 1. To large models than to small models; and 2. As models were brought closer. Solitary damselfish showed stronger responses than did fish in small groups. However, no habituation to threat occurred, no correlation was found between response strength and fish size, and many individuals gave strong, ungraded responses to predator models. Comparisons between juvenile bicolor damselfish and threespot damselfish suggest that bicolor are weakly threat sensitive in that they respond strongly regardless of threat (hypersensitivity). Solitary fish are more hypersensitive than grouped fish. Threespot damselfish show a stronger influence of damselfish body size: small threespot exhibit graded responses in proportion to degree of threat (pure threat sensitivity), whereas large threespot show relatively weak responses (nonchalance). These interspecific comparisons indicate the potential range that characterizes threat sensitivity and the possible influence of social and ontogenetic factors on that range.     

Physiological Plasticity to Water Flow Habitat in the Damselfish,Acanthochromis polyacanthus: Linking Phenotype to Performance

The relationships among animal form, function and performance are complex, and vary across environments. Therefore, it can be difficult to identify morphological and/or physiological traits responsible for enhancing performance in a given habitat. In fishes, differences in swimming performance across water flow gradients are related to morphological variation among and within species. However, physiological traits related to performance have been less well studied. We experimentally reared juvenile damselfish, Acanthochromis polyacanthus, under different water flow regimes to test 1) whether aspects of swimming physiology and morphology show plastic responses to water flow, 2) whether trait divergence correlates with swimming performance and 3) whether flow environment relates to performance differences observed in wild fish. We found that maximum metabolic rate, aerobic scope and blood haematocrit were higher in wave-reared fish compared to fish reared in low water flow. However, pectoral fin shape, which tends to correlate with sustained swimming performance, did not differ between rearing treatments or collection sites. Maximum metabolic rate was the best overall predictor of individual swimming performance; fin shape and fish total length were 3.3 and 3.7 times less likely than maximum metabolic rate to explain differences in critical swimming speed. Performance differences induced in fish reared in different flow environments were less pronounced than in wild fish but similar in direction. Our results suggest that exposure to water motion induces plastic physiological changes which enhance swimming performance in A. polyacanthus. Thus, functional relationships between fish morphology and performance across flow habitats should also consider differences in physiology.     

What can imaging tell us about physiology? Lung growth and regional mechanical strain

The interplay of mechanical forces transduces diverse physico-biochemical processes to influence lung morphogenesis, growth, maturation, remodeling and repair. Because tissue stress is difficult to measure in vivo, mechano-sensitive responses are commonly inferred from global changes in lung volume, shape, or compliance and correlated with structural changes in tissue blocks sampled from postmortem-fixed lungs. Recent advances in noninvasive volumetric imaging technology, nonrigid image registration, and deformation analysis provide valuable tools for the quantitative analysis of in vivo regional anatomy and air and tissue-blood distributions and when combined with transpulmonary pressure measurements, allow characterization of regional mechanical function, e.g., displacement, strain, shear, within and among intact lobes, as well as between the lung and the components of its container-rib cage, diaphragm, and mediastinum-thereby yielding new insights into the inter-related metrics of mechanical stress-strain and growth/remodeling. Here, we review the state-of-the-art imaging applications for mapping asymmetric heterogeneous physical interactions within the thorax and how these interactions permit as well as constrain lung growth, remodeling, and compensation during development and following pneumonectomy to illustrate how advanced imaging could facilitate the understanding of physiology and pathophysiology. Functional imaging promises to facilitate the formulation of realistic computational models of lung growth that integrate mechano-sensitive events over multiple spatial and temporal scales to accurately describe in vivo physiology and pathophysiology. Improved computational models in turn could enhance our ability to predict regional as well as global responses to experimental and therapeutic interventions.     

Electrical responses to water‐soluble components of fish mucus recorded from the cnidocytes of a fish predator,Physalia physalis

Physalia physalis, the Portuguese man of war, consumes mostly fish and fish larvae. Intracellular recordings from nematocyst‐containing cells (cnidocytes) in small pieces of Physalia tentacle were used to quantify the electrical responses to diluted and filtered fish skin mucus, 1–100 x 10^‐6 M amino acids, monosaccharides, and nucleosides, and seawater, which were delivered upstream of the tissue. Seawater caused responses (one pulse only) in about 10% of the applications. Fish mucus extract elicited responses in all applications, producing 1–18 depolarizing pulses (20 mV maximum amplitude). The pulses were characteristic of post‐synaptic potentials (EPSPs). Lucifer yellow and biocytin dye injections showed that the cnidocytes were not electrically coupled. Simultaneous records from two cnidocytes following mucus applications were identical.We propose, therefore, that the chemoreceptors are not on the cnidocytes, but are probably on sensory neurons that innervate clusters of cnidocytes. A < 3,000 MW fraction of mucus elicited responses indistinguishable from whole mucus extract. Higher molecular weight fractions caused no response. The various test solutions had lower percentages of response (47–92%) and produced significantly fewer pulses than the mucus extract. We conclude that prey capture in Physalia is facilitated by chemicals present in the mucus covering their fish prey. The chemical stimuli probably sensitize the nematocysts to discharge upon mechanical stimulation.     

Novel protein carrier system based on cyanobacterial nano-sized extracellular vesicles for application in fish

Aquaculture has been one of the fastest-growing food industry sectors, expanding at the pace of consumers' demands. To promote safe and effective fish growth performance strategies, and to stimulate environmentally friendly solutions to protect fish against disease outbreaks, new approaches are needed to safeguard fish welfare, as well as farmers and consumers interests. Here, we tested the use of cyanobacterial extracellular vesicles (EVs) as a novel nanocarrier system of heterologous proteins for applications in fish. We started by incubating zebrafish larvae with Synechocystis sp. PCC6803 EVs, isolated from selected mutant strains with different cell envelope characteristics. Results show that Synechocystis EVs are biocompatible with fish larvae, regardless of their structural composition, as EVs neither induced fish mortality nor triggered significant inflammatory responses. We establish also that cyanobacteria are amenable to engineering heterologous protein expression and loading into EVs, for which we used the reporter sfGFP. Moreover, upon immersion treatment, we successfully demonstrate that sfGFP-loaded Synechocystis EVs accumulate in the gastrointestinal tract of zebrafish larvae. This work opens the possibility of using cyanobacterial EVs as a novel biotechnological tool in fish, with prospective applications in carrying proteins/enzymes, for example for modulating their nutritional status or stimulating specific adaptive immune responses.     

Uncovering physiologic mechanisms of circadian rhythms and sleep/wake regulation through mathematical modeling

Mathematical models of neurobehavioral function are useful both for understanding the underlying physiology and for predicting the effects of rest-activity-work schedules and interventions on neurobehavioral function. In a symposium titled "Modeling Human Neurobehavioral Performance I: Uncovering Physiologic Mechanisms" at the 2006 Society for Industrial and Applied Mathematics/Society for Mathematical Biology (SIAM/SMB) Conference on the Life Sciences, different approaches to modeling the physiology of human circadian rhythms, sleep, and neurobehavioral performance and their usefulness in understanding the underlying physiology were examined. The topics included key elements of the physiology that should be included in mathematical models, a computational model developed within a cognitive architecture that has begun to include the effects of extended wake on information-processing mechanisms that influence neurobehavioral function, how to deal with interindividual differences in the prediction of neurobehavioral function, the applications of systems biology and control theory to the study of circadian rhythms, and comparisons of these methods in approaching the overarching questions of the underlying physiology and mathematical models of circadian rhythms and neurobehavioral function. A unifying theme was that it is important to have strong collaborative ties between experimental investigators and mathematical modelers, both for the design and conduct of experiments and for continued development of the models.     

Comparative physiology and biochemistry: challenges for the future

1. Comparative physiology is distinguished from other types of physiology by treating the diversity of solutions of functional problems and by using kind of animal as a functional variable. 2. The strength of comparative physiology os its capacity to give some solutions to problems in basic biology. 3. Specific examples of subject areas to which comparative physiology contributes are: (a) mechanisms underlying evolution; (b) the nature of speciation; (c) comparative cognitive science, neural models for behavior; and (d) applications of molecular techniques to physiology of whole animals. 4. Applications continue in ecology, medicine and agriculture. 5. The breadth of the comparative approach to physiology has important philosophical implications.