Adapting Management of Marine Environments to a Changing Climate: A Checklist to Guide Reform and Assess Progress

Documented impacts of climate change on marine systems indicate widespread changes in many geographic regions and throughout all levels of the ocean’s food webs. Oceans provide the main source of animal protein for over a billion people, and contribute significantly to food security for billions more. Clearly, if we are to continue to derive these benefits, then the rate of adaptation in our human systems needs to at least keep pace with the rate of ecological change for these benefits to continue. An Australia-wide program of research into marine biodiversity and fisheries explored the opportunities for policy and management to respond to a changing climate. The research program spanned all Australian estuarine-nearshore and marine environments—tropical, subtropical, and temperate—and focused on two key marine sectors: biodiversity conservation and fisheries (commercial, recreational, and aquaculture). Key findings from across this strategic and extensive research investment were the need to foster resilience through habitat repair and protection, improve resource allocation strategies, fine-tune fisheries management systems, and enhance whole of government approaches and policies. Building on these findings, from a climate adaptation perspective, we generated a checklist of thirteen elements encompassing all project findings to assess and steer progress towards improving marine policy and management. These elements are grouped in three broad areas: preconditioning; future proofing; and transformational changes and opportunities. Arising from these elements is a suite of priority strategies that provide guidance for marine managers, policy practitioners, and stakeholders as they prepare for a future under climate change. As the research program encompassed a wide range of habitats and ecosystems, spanned a latitudinal range of over 30°, and considered a diversity of management systems and approaches, many of these elements and strategies will be applicable in a global context.     

Ventilatory Responses of Teleost Fish to Exercise and Thermal Stress

Exercise and thermal stress both markedly raise the oxygen demandof fish. The control of ventilation under these two conditionsis apparently quite different and contrasts between speciesare noteworthy. Under both exercise and thermal stress, changes in respiratorypumping amplitude tend to be greater than changes in ventilatoryfrequency in most species. Respiratory pump uncoupling duringthermal stress is frequently seen in trout but much less soin bullhead catfish or bluegills. In fish that actively ventilate the gills while swimming, thecontrol for this probably depends on swimming muscle reflexesrather than blood humoral factors. This control mechanism mayoperate in a reverse fashion in fish that use ram-jet ventilation.During recovery from severe exercise and during thermal stressthe control of gill ventilation is apparently humoral. Of thepossible factors, blood oxygen and possibly also pH are consideredto be the most important. Evidence is summarized that suggeststhe error detector is on the arterial side of the gas exchanger.     

Endocrine Control of Osmoregulation in Teleost Fish

As the primary link between environmental change and physiologicalresponse, the neuroendocrine system is a critical part of osmoregulatoryadaptations. Cortisol has been viewed as ‘the’ seawater-adaptinghormone in fish and prolactin as ‘the’ fresh wateradapting hormone. Recent evidence indicates that the growthhormone/insulin-like growth factor I axis is also importantin seawater adaptation in several teleosts of widely differingevolutionary lineages. In salmonids, growth hormone acts insynergy with cortisol to increase seawater tolerance, at leastpartly through the upregulation of gill cortisol receptors.Cortisol under some conditions may promote ion uptake and interactswith prolactin during acclimation to fresh water. The osmoregulatoryactions of growth hormone and prolactin are antagonistic. Insome species, thyroid hormones support the action of growthhormone and cortisol in promoting seawater acclimation. Althougha broad generalization that holds for all teleosts is unlikely,our current understanding indicates that growth hormone promotesacclimation to seawater, prolactin promotes acclimation to freshwater, and cortisol interacts with both of these hormones thushaving a dual osmoregulatory function.     

Endocrine Factors Affecting Thyroid Economy of Teleost Fish

SYNOPSIS. This review examines the way in which the activityof the hypothalamo-pituitary-thyroid axis in teleost fishesis modified by pituitary, steroid and amine hormones. Thesefactors may act at the level of the hypothalamus, the pituitarygland (thyrotrops), the thyroid gland, or the peripheral tissues,and affect thyroid hormone synthesis, release, metabolism, ordegradation. With few exceptions, the studies are limited toonly a few species, the results are often fragmentary and contradictory,are based on experiments in which pharmacological, rather thanphysiological, hormone ranges have been used, and there is toolittle information to establish a consistent pattern of responseto endocrines other than those which are components of the hypothalamo-pituitary-thyroidaxis itself. Most studies evaluating the effects of pituitaryhormones on thyroid economy in fish have, of necessity, reliedon mammalian preparations. Some of these (e.g., prolactin andthe gonadotropins) elicit very different responses from thoseof the equivalent semipurified or purified piscine hormone,although mammalian and piscine TSH and GH respectively appearto elicit similar responses in the teleostean thyroid system.The elevation of plasma T₄ levels in response to a challengeof exogenous TSH has been used in several studies as a way ofevaluating the sensitivity of the thyroid to TSH; the responseis modified by photoperiod, season, stage of development, estrogenand corticosteroids.     

Peculiarities of Structure, Polymorphism, and Resistance to Oxidation of Fish Hemoglobins

The paper presents data on peculiarities of structural organization of fish hemoglobin molecules. The existence of symmetric and asymmetric complexes and their importance for formation in some types of complex heterogeneous hemoglobin systems is considered. The comparative characteristics of the primary structure of - and -chains of the respiratory pigments in higher and lower vertebrates are presented. The causes of low resistance of fish hemoglobins to oxidation are discussed. Protective action of Cl^– under conditions of nitrite intoxication, as well as role of several intraerythrocytic molecular systems in maintaining the pigment ferroform (superoxide dismutase, catalase, peroxidase, and NADH-diaphorase) are considered.     

Molecular Evolution of Teleost Neural Isozymes

Isozymes, homologous enzymes coded by separate loci within a genome, present interesting systems for examining molecular and functional divergence through natural selection. Isozyme pairs for a number of metabolic enzymes, including Triosephosphate isomerase (Tpi), Malate dehydrogenase (Mdh), Phosphoglucose isomerase (Pgi), and Guanylate kinase (Guk), appear to all result from a single, large duplication event early in teleost evolution. These small gene families include two forms, a generally expressed form with no apparent charge and a neurally expressed form with a pronounced negative charge although the canalization of expression of the second form varies across families. Using ancestral sequence reconstructions and standard comparisons of rates of nonsynonymous and synonymous change, combined with the examination of the specific amino acid changes observed and predicted we examined the evolution of the Tpi and Guk families using all available vertebrate sequences and all four families using a smaller, common, dataset. We find that post-duplication, the neural Tpi and Guk isozymes evolved through similar periods of positive selection as evidenced by elevated rates of nonsynonymous change and accumulation of negative amino acids. Over the same evolutionary period our analysis suggests that Mdh and Pgi isozymes appear to have evolved under a less divergent pattern of selection. These distinct results likely reflect functional differences between the isozymes, possibly a result of differences in expression patterns.     

Conservation of Toll-Like Receptor Signaling Pathways in Teleost Fish

In mammals, toll-like receptors (TLR) recognize ligands, including pathogen-associated molecular patterns (PAMPs), and respond with ligand-specific induction of genes. In this study, we establish evolutionary conservation in teleost fish of key components of the TLR-signaling pathway that act as switches for differential gene induction, including MYD88, TIRAP, TRIF, TRAF6, IRF3, and IRF7. We further explore this conservation with a molecular phylogenetic analysis of MYD88. To the extent that current genomic analysis can establish, each vertebrate has one ortholog to each of these genes. For molecular tree construction and phylogeny inference, we demonstrate a methodology for including genes with only partial primary sequences without disrupting the topology provided by the high-confidence full-length sequences. Conservation of the TLR-signaling molecules suggests that the basic program of gene regulation by the TLR-signaling pathway is conserved across vertebrates. To test this hypothesis, leukocytes from a model fish, rainbow trout (Oncorhynchus mykiss), were stimulated with known mammalian TLR agonists including: diacylated and triacylated forms of lipoprotein, flagellin, two forms of LPS, synthetic double-stranded RNA, and two imidazoquinoline compounds (loxoribine and R848). Trout leukocytes responded in vitro to a number of these agonists with distinct patterns of cytokine expression that correspond to mammalian responses. Our results support the key prediction from our phylogenetic analyses that strong selective pressure of pathogenic microbes has preserved both TLR recognition and signaling functions during vertebrate evolution.     

Evolution and Expression of Paxillin Genes in Teleost Fish

BackgroundPaxillin family proteins regulate intracellular signaling downstream of extracellular matrix adhesion. Tissue expression patterns and cellular functions of Paxillin proteins during embryo development remain poorly understood. Additionally, the evolution of this gene family has not been thoroughly investigated.ResultsThis report characterizes the evolution and expression of a novel Paxillin gene, called Paxillin-b, in Teleosts. Alignments indicate that Teleost Paxillin-a and Paxillin-b proteins are highly homologous to each other and to human Paxillin. Phylogenetic and synteny analyses suggest that these genes originated from the duplication of an ancestral Paxillin gene that was in a common ancestor of Teleosts and Tetrapods. Analysis of the spatiotemporal expression profiles of Paxillin-a and Paxillin-b using zebrafish revealed both overlapping and distinct domains for Paxillin-a and Paxillin-b during embryo development. Localization of zebrafish Paxillin orthologs expressed in mammalian cells demonstrated that both proteins localize to focal adhesions, similar to mammalian Paxillin. This suggests these proteins regulate adhesion-dependent processes in their endogenous tissues.ConclusionPaxillin-a and Paxillin-b were generated by duplication in Teleosts. These genes likely play similar roles as Paxillin genes in other organisms. This work provides a framework for functional investigation of Paxillin family members during development using the zebrafish as an in vivo model system.     

硬骨鱼新型免疫球蛋白的研究进展

鱼类是最早出现免疫球蛋白的动物,鱼类免疫球蛋白在鱼类的特异性体液免疫应答中发挥重要的作用。一直以来,人们认为在硬骨鱼中仅存在IgM和IgD两种免疫球蛋白,而2005年以来,陆续在斑马鱼、虹鳟鱼及鲤鱼等硬骨鱼中发现了新型免疫球蛋白,分别命名为IgZ、IgT及IgM-IgZ等。这些新型免疫球蛋白不仅在基因结构上很特别,而且呈现出多样性,在不同种的硬骨鱼中的功能也不完全相同,同一种鱼中的IgT也呈现多样性。虽然目前对于鱼类新型免疫球蛋白的研究刚刚起步,对其功能了解较少,但有研究表明IgT在硬骨鱼的粘膜免疫中发挥重要的作用,且认为它与IgA是同源的。该文拟对硬骨鱼中发现的新型免疫球蛋白的结构特点、基因组成和分布模式及功能差异作一简要综述。     

Ultrastructural Distribution of Calcium in Cutaneous Electroreceptor Organs of Teleost Fish

The calcium distribution in the ampullary electroreceptor and the type B electrore-ceptor organ (gymnarchomast) of Gymnarchus niloticus (Gymnarchidae) and in the tuberous organ of Apteronotus leptorhynchus (gymnotidae) was studied. Endogenous calcium appeared as electron-dense precipitates when the cutaneous organs were pre-fixed with phosphate-buffered glutaraldehyde and postfixed with osmium tetroxide plus potassium bichromate. Calcium precipitates were localized in both intracellular compartments of sensory cells and afferent nerve fibers. In contrast to sensory cells, small amounts of calcium precipitates were found in the cytoplasm of accessory cells. In sensory cells, electron-dense deposits were apparent mainly in synaptic vesicles near synaptic ribbons, inside vacuoles of the endoplasmic reticulum, and between the layers of the nuclear membrane. Very few deposits were found in mitochondria. Precipitates were also observed within the axons of afferent nerves and between the layers of the myelin sheath. The synaptic cleft was devoid of calcium. Calcium deposits have a specific cellular distribution in electro-receptor organs of teleost fish.     

Molecular Studies on the Ecology of Listeria monocytogenes in the Smoked Fish Processing Industry

We have applied molecular approaches, including PCR-based detection strategies and DNA fingerprinting methods, to study the ecology of Listeria monocytogenes in food processing environments. A total of 531 samples, including raw fish, fish during the cold-smoking process, finished product, and environmental samples, were collected from three smoked fish processing facilities during five visits to each facility. A total of 95 (17.9%) of the samples tested positive for L. monocytogenes using a commercial PCR system (BAX for Screening/Listeria monocytogenes), including 57 (27.7%) environmental samples (n = 206), 8 (7.8%) raw material samples (n = 102), 23 (18.1%) samples from fish in various stages of processing(n = 127), and 7 (7.3%) finished product samples (n = 96). L. monocytogenes was isolated from 85 samples (16.0%) using culture methods. Used in conjunction with a 48-h enrichment in Listeria Enrichment Broth, the PCR system had a sensitivity of 91.8% and a specificity of 96.2%. To track the origin and spread of L. monocytogenes, isolates were fingerprinted by automated ribotyping. Fifteen different ribotypes were identified among 85 isolates tested. Ribotyping data established possible contamination patterns, implicating raw materials and the processing environment as potential sources of finished product contamination. Analysis of the distribution of ribotypes revealed that each processing facility had a unique contamination pattern and that specific ribotypes persisted in the environments of two facilities over time (P ≤ 0.0006). We conclude that application of molecular approaches can provide critical information on the ecology of different L. monocytogenes strains in food processing environments. This information can be used to develop practical recommendations for improved control of this important food-borne pathogen in the food industry.     

Effects of Temperature, pH, and Organic Phosphates on Fish Hemoglobins

This review presents data on effects of temperature, pH, and organic phosphates on structural-functional characteristics of fish hemoglobins. Special attention is paid to the structure of pigments insensitive to pH as well as those that have the reverse Bohr effect in alkaline range of pH. The role of surface -adrenoreceptors and activity of Na⁺/H⁺ exchanger in regulation of the acid-base equilibrium of intraerythrocyte medium are considered. There are compared characteristics of participation of nucleotide triphosphates, 2,3-DPG, and other organic phosphates in correction of fish hemoglobin affinity to oxygen. The values of H for fish respiratory pigments are presented, and their dependence on conditions of erythrocyte microsurrounding is discussed.     

Ecology of Vibrio mimicus in Aquatic Environments

[This corrects the article on p. 2077 in vol. 55.].     

Short Inverted-Repeat Transposable Elements in Teleost Fish and Implications for a Mechanism of Their Amplification

Angel is the first miniature inverted-repeat transposable element (MITE) isolated from fish. Angel elements are imperfect palindromes with the potential to form stem-loop structures in vitro. Despite sequence divergence of elements of up to 55% within and between species, their inverted repeat structures have been maintained, implying functional importance. We estimate that there are about 10³–10⁴ Angels scattered throughout the zebrafish genome, evidence that this family of transposable elements has been significantly amplified over the course of evolution. Angel elements and Xenopus MITEs carry common sequence motifs at their termini, indicating common origin and/or related mechanisms of transposition. We present a model in which MITEs take advantage of the basic cellular mechanism of DNA replication for their amplification, which is dependent on the characteristic inverted repeat structures of these elements. We propose that MITEs are genomic parasites that transpose via a DNA intermediate, which forms by a folding-back of a single strand of DNA, that borrow all of the necessary factors for their amplification from products encoded in the genomes in which they reside. DNA polymorphisms in different lines of zebrafish were detected by PCR using Angel-specific primers, indicating that such elements, combined with other transposons in vertebrate genomes, will be useful molecular tools for genome mapping and genetic analyses of mutations. Received: 7 April 1998 / Accepted: 7 April 1998     

Structure of Annelid High Molecular Weight Hemoglobins (Erythrocruorins)

The extracellular vascular hemoglobins (erythrocruorins) ofannelids are polymeric oxygen carriers with molecular weightsof approximately 3 x 10⁶ or about 46 times the molecular weightof a vertebrate hemoglobin tetramer. The molecule appears asa dodecamer of 12 large submultiples arranged at the verticesof two regular hexagons one on top of the other in electronmicrographs. The dimensions are about 250 Å across theface of the hexagon and about 170 Å in height. The molecularweight of a one-twelfth submultiple is approximately 250 000.Biochemical studies suggest that each submultiple contains 16to 18 subunits and that the intact hemoglobin molecule containsapproximately 200 subunits. Unlike vertebrate hemoglobin whichcontains one heme moiety for each polypeptide chain the annelidhemoglobins apparently contain one heme per 15 to 20 chains.The reasons for this lack of a 11 heme chain stoichiometry arenot known at present. One possibility may be that it is theresult of insufficient purification of the hemoglobin. Alternatively,more than one globin chain might share a heme certain globinchains might lack the heme moiety and have a non hemoglobinfunction, or certain globin chains may lose their heme duringpurification of the hemoglobin. We are presently determiningthe amino acid sequence of one globin chain of Lumbricus terrestrishemoglobin. This information should be helpful in understandingthe structure of these interesting polymers.