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Variation in oxygen consumption and temperature preference of Atlantic cod, Gadus morhua, from Denmark and Greenland
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Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S203–S210
marine populations. To improve current diagnostic and prognostic abilities there is a need for better understanding of the processes by which these environmental events select for phenotypes and influence intraspecific trait variation. Various studies have investigated which physiological traits might define successful phenotypes in a given environment. Very few of these, however, have been on marine fish, in large part due to the technical difficulties of studying them in their natural environment, and the logistics required to combine laboratory and field experiments. We will argue, however, that this is not the main problem. It is our view that, contrary to examples from the medical sciences, environmental physiology has not been able to create truly diagnostic and prognostic tools from the large available database of mechanistic physiological information. As a result, the links between suborganismal traits of performance and the dynamics and productivity of populations remain to be defined, even in unperturbed environments. Understanding these links will be essential to forecast the impact of anthropogenic induced environmental changes on marine fish populations. From this perspective, notions such as inter-individual variability, temporal stability or adaptive significance needs to be given more appropriate consideration by physiologists. doi:10.1016/j.cbpa.2008.04.576
SETE.14 Population studies vs. physiology: Methodological approach to resting metabolic rate determination in fish populations W. Waser (University of Turku)
The successful merging of populations studies (Ecological Genetics, Molecular Ecology and Evolution Research) with (especially: live animal) physiology is predominantly impeded by the necessity of combining a) the large number of animals generally required for the former fields of inquiry and b) the technical efforts unavoidable for the latter. On the molecular level (“genomics”, “proteomics”) high throughput is more easily achieved, leading to increased use of molecular techniques in population studies. Investigations of whole organism's integrated responses within and between populations, however, are still few and far in between. To reduce the gap between necessity of large numbers and technical effort, an experimental setup to screen resting metabolic rate (i.e. oxygen consumption) in populations of small fish was devised. Screening of a few hundred fish is within the realms of possibility, but current conceptual and technical constrains still would make this an undertaking lasting several weeks. In a first evaluation, six populations of 9-spined sticklebacks collected in Sweden, Finland, and Russia were measured, showing no significant differences in metabolic rate between the groups. Also, the effect of different copper concentrations on metabolic rate was investigated in several groups of 9-spined sticklebacks. The multiplex setup for metabolic rate measurement enables the collection of data from a comparatively large number of fish, while still leaving the fish available for further molecular and genetic analyses.
doi:10.1016/j.cbpa.2008.04.577
SETE.15 Intraspecific variation in genotype, morphology and performance: Contribution to ecological performance and mortality selection in cultured and wild European sea bass (Dicentrarchus labrax) J. Nelson (Towson University); C. Handelsmann (Colorado State University); C. Sinclair (Towson University); G. Claireaux (Universite' de Bretagne Occidentale)
Understanding natural selection requires knowledge of phenotypic selection and the heritability of traits that make successful phenotypes. Identification of key traits is difficult in most systems, but in marine fishes, the relationships among performance, morphological and physiological traits, genotype and animal success in nature are virtually unknown. A cohort of 120 cultured fish was genotyped using seven species-specific microsatellite primers on fin clip DNA, characterized for body morphology with geometric morphometric techniques, and measured for sprint and endurance performance. Fish were subsequently released into estuaries for 6 months at densities that ensured competition for natural forage. A second experiment exposed replicate groups of cultured and wild fish of known morphology and print capacity to avian predation in the estuaries for 14 weeks. Substantial intraspecific variation was found in all measured parameters. Growth in the estuaries was genotype-dependent and morphology correlated with survival of cultured fish. Growth rate was predictive of survival and was inversely correlated to swimming performance. Wild fish were faster than cultured fish and experienced lower mortality (65% vs. 100%) under the selective regime in the estuaries, despite being significantly smaller. Both juvenile and adult sea bass captured in the wild exhibited only a subset of the morphological variation found in cultured fish. Interestingly, cultured fish with similar morphology to wild fish were significantly faster than other cultured fish. This suggests that, if the complete range of phenotypes is represented by cultured fish, significant stabilizing selection occurs at early life history stages in the wild. doi:10.1016/j.cbpa.2008.04.578
SETE.16 Variation in oxygen consumption and temperature preference of Atlantic cod, Gadus morhua, from Denmark and Greenland J. Steffensen (University of Copenhagen) A study of Gadoid metabolism in Greenland, concerning metabolic cold adaptation, found no significant difference in standard metabolic rates between the Arctic Boreogadus saida and Gadus ogac, or the temperate Atlantic cod (Gadus morhua), when measured at 4 °C. If however comparing metabolic rates of Atlantic cod at a temperature of 4–5 °C from Greenland with fish from Denmark, the Greenland fish had considerable higher values. In 1961 Sick showed that Atlantic cod haemoglobin is polymorph and consists of two homozygous genotypes (HbI-1 and HbI-2) and one heterozygous genotype (HbI-1/2). The genotypes are controlled by two alleles referred to as HbI1and HbI2. The frequency distribution of the two alleles is heterogeneous across the North Atlantic with 99% of HbI2 in waters around Greenland, northernmost Norway and in the Baltic Sea, while the HbI1is dominant in warmer waters. Is this the reason for the difference in metabolic rate between fish from Greenland and Denmark?
Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S203–S210
In Denmark cod with all three genotypes can be caught, and experiments with a shuttle box showed that the preferred temperature of HbI-1 and HbI-2 was 15.4 and 8.2 °C, respectively. When exposed to hypoxia the preferred temperature of HbI-1 cod changed from 15.4 to 9.8 °C, while the HbI-2 cod showed no effect. McFarland compared oxygen consumption of cod caught in Denmark with haemoglobin type HbI-1 and HbI-2, but found no significant difference, so it is still unknown why Greenland Atlantic cod have a higher metabolic rate.
doi:10.1016/j.cbpa.2008.04.579
SETE.17 Why hypoxic bradycardia in fishes? A. Farrell (University of British Columbia) Why do certain fish respond to environmental hypoxia with bradycardia whereas mammals respond with tachycardia? Equivocal results regarding a potential benefit to gill oxygen transfer open the door for the present analysis of potential benefits of hypoxic bradycardia to cardiac function. The potential benefits, which include improving contractility through a negative force frequency effect, reducing cardiac oxygen demand by improving mechanical efficiency, and improving cardiac oxygen delivery to trabecular and compact cardiac muscle, recognize the ability of the fish heart to considerably vary stroke volume and its reliance on oxygen contained invenous blood. Further insights to the benefits of hypoxic bradycardia are provided by the observations that anemic trout, Antarctic fish, anoxia-tolerant fishes and air breathing fishes do not display hypoxic bradycardia. Research support provided by NSERC Canada. doi:10.1016/j.cbpa.2008.04.580
SETE.18 Temperature tolerance and respiration in coral reef fishes G. Nilsson (University of Oslo) Abstract not available. doi:10.1016/j.cbpa.2008.04.581
SETE.19 Intra-specific variation in muscle fibre phenotype I.A. Johnston, I.P.G. Amaral, V.L.A. Vieira (University of St Andrews) The large increase in body size observed between larval and adult fish requires the continuous production of fast myotomal muscle fibres until around 40% of the maximum length. Subsequent growth in myotomal girth only involves fibre hypertrophy, although myotubes can still be produced to repair damage following injury. The optimal fibre number hypothesis provides a physiological explanation for changes in final fibre
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number (FFN) with body size and environment. The hypothesis envisages an optimal fibre number which minimises the energy costs of maintaining ionic homeostasis in the muscle (Johnston et al., 2003, 2006). This presentation will consider various tests of the optimal fibre number hypothesis in marine and anadromous fishes and examine the relative importance of selection and developmental plasticity in generating the observed variation in FFN between populations. Recent genomic approaches to investigate the control of fibre number and experiments to determine the consequences of intraspecific variation in FFN for whole animal performance will be discussed. Johnston, I.A., Fernandez, D., Calvo, J., Vieira, V.L.A., North, T.W., Abercromby, M., and Garland, T. Jr. (2003). Reduction in muscle fibre number during the adaptive radiation of Notothenioid fishes: a phylogenetic perspective. J. Exp. Biol. 206, 25952609. Johnston, I.A., Abercromby, M., and Andersen, Ø. (2006). Muscle fibre number varies with haemoglobin phenotype in Atlantic cod as predicted by the optimal fibre number hypothesis. Biol. Lett. 2, 590592. doi:10.1016/j.cbpa.2008.04.582
SETE.20 Haemoglobin polymorphism and red blood cell sickling in marine fishes M. Berenbrink (University of Liverpool); D. McDonald (University of Miami); P. Koldkjaer (University of Liverpool)
In human sickle cell disease a single surface amino acid mutation in the beta globin chain leads to the formation of large insoluble haemoglobin (Hb) aggregates at low oxygen tension. This may cause peculiar cell deformations or ‘sickling’, which can cause vascular occlusion, organ failure and death. In a classic example of balanced polymorphism, the frequency of the mutated beta-globin allele is kept elevated in certain human populations because of the benefits for heterozygote carriers against infection with malaria parasites. In vitro, red blood cell sickling is also found in several marine fish species such as the oyster toadfish, Atlantic cod and other codfishes (Harison et al., 1998). Recently, we have demonstrated its occurrence in vivo in whiting, Merlangus merlangius, and suggested that it may be involved in protection against parasite infection (Koldkjaer and Berenbrink, 2007). However, the molecular and genetic bases of sickling in marine fishes are poorly understood. Here we describe large intraspecific differences in red blood cell sickling in the Gulf toadfish Opsanus beta, which are associated with a complex Hb polymorphism. In contrast, we show that in Atlantic cod nearly 100% sickling can be induced in all Hb genotypes that comprise the well-known HbI polymorphism. These results indicate distinct intra and interspecific differences in red blood cell sickling in marine fishes, although its relative costs and benefits remain to be established. References Harosi, et al., 1998. Biol. Bull. 195, 5–11. Koldkjaer, Berenbrink, 2007. J. Exp. Biol. 210, 3451–3460. doi:10.1016/j.cbpa.2008.04.583
Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S203–S210
marine populations. To improve current diagnostic and prognostic abilities there is a need for better understanding of the processes by which these environmental events select for phenotypes and influence intraspecific trait variation. Various studies have investigated which physiological traits might define successful phenotypes in a given environment. Very few of these, however, have been on marine fish, in large part due to the technical difficulties of studying them in their natural environment, and the logistics required to combine laboratory and field experiments. We will argue, however, that this is not the main problem. It is our view that, contrary to examples from the medical sciences, environmental physiology has not been able to create truly diagnostic and prognostic tools from the large available database of mechanistic physiological information. As a result, the links between suborganismal traits of performance and the dynamics and productivity of populations remain to be defined, even in unperturbed environments. Understanding these links will be essential to forecast the impact of anthropogenic induced environmental changes on marine fish populations. From this perspective, notions such as inter-individual variability, temporal stability or adaptive significance needs to be given more appropriate consideration by physiologists. doi:10.1016/j.cbpa.2008.04.576
SETE.14 Population studies vs. physiology: Methodological approach to resting metabolic rate determination in fish populations W. Waser (University of Turku)
The successful merging of populations studies (Ecological Genetics, Molecular Ecology and Evolution Research) with (especially: live animal) physiology is predominantly impeded by the necessity of combining a) the large number of animals generally required for the former fields of inquiry and b) the technical efforts unavoidable for the latter. On the molecular level (“genomics”, “proteomics”) high throughput is more easily achieved, leading to increased use of molecular techniques in population studies. Investigations of whole organism's integrated responses within and between populations, however, are still few and far in between. To reduce the gap between necessity of large numbers and technical effort, an experimental setup to screen resting metabolic rate (i.e. oxygen consumption) in populations of small fish was devised. Screening of a few hundred fish is within the realms of possibility, but current conceptual and technical constrains still would make this an undertaking lasting several weeks. In a first evaluation, six populations of 9-spined sticklebacks collected in Sweden, Finland, and Russia were measured, showing no significant differences in metabolic rate between the groups. Also, the effect of different copper concentrations on metabolic rate was investigated in several groups of 9-spined sticklebacks. The multiplex setup for metabolic rate measurement enables the collection of data from a comparatively large number of fish, while still leaving the fish available for further molecular and genetic analyses.
doi:10.1016/j.cbpa.2008.04.577
SETE.15 Intraspecific variation in genotype, morphology and performance: Contribution to ecological performance and mortality selection in cultured and wild European sea bass (Dicentrarchus labrax) J. Nelson (Towson University); C. Handelsmann (Colorado State University); C. Sinclair (Towson University); G. Claireaux (Universite' de Bretagne Occidentale)
Understanding natural selection requires knowledge of phenotypic selection and the heritability of traits that make successful phenotypes. Identification of key traits is difficult in most systems, but in marine fishes, the relationships among performance, morphological and physiological traits, genotype and animal success in nature are virtually unknown. A cohort of 120 cultured fish was genotyped using seven species-specific microsatellite primers on fin clip DNA, characterized for body morphology with geometric morphometric techniques, and measured for sprint and endurance performance. Fish were subsequently released into estuaries for 6 months at densities that ensured competition for natural forage. A second experiment exposed replicate groups of cultured and wild fish of known morphology and print capacity to avian predation in the estuaries for 14 weeks. Substantial intraspecific variation was found in all measured parameters. Growth in the estuaries was genotype-dependent and morphology correlated with survival of cultured fish. Growth rate was predictive of survival and was inversely correlated to swimming performance. Wild fish were faster than cultured fish and experienced lower mortality (65% vs. 100%) under the selective regime in the estuaries, despite being significantly smaller. Both juvenile and adult sea bass captured in the wild exhibited only a subset of the morphological variation found in cultured fish. Interestingly, cultured fish with similar morphology to wild fish were significantly faster than other cultured fish. This suggests that, if the complete range of phenotypes is represented by cultured fish, significant stabilizing selection occurs at early life history stages in the wild. doi:10.1016/j.cbpa.2008.04.578
SETE.16 Variation in oxygen consumption and temperature preference of Atlantic cod, Gadus morhua, from Denmark and Greenland J. Steffensen (University of Copenhagen) A study of Gadoid metabolism in Greenland, concerning metabolic cold adaptation, found no significant difference in standard metabolic rates between the Arctic Boreogadus saida and Gadus ogac, or the temperate Atlantic cod (Gadus morhua), when measured at 4 °C. If however comparing metabolic rates of Atlantic cod at a temperature of 4–5 °C from Greenland with fish from Denmark, the Greenland fish had considerable higher values. In 1961 Sick showed that Atlantic cod haemoglobin is polymorph and consists of two homozygous genotypes (HbI-1 and HbI-2) and one heterozygous genotype (HbI-1/2). The genotypes are controlled by two alleles referred to as HbI1and HbI2. The frequency distribution of the two alleles is heterogeneous across the North Atlantic with 99% of HbI2 in waters around Greenland, northernmost Norway and in the Baltic Sea, while the HbI1is dominant in warmer waters. Is this the reason for the difference in metabolic rate between fish from Greenland and Denmark?
Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S203–S210
In Denmark cod with all three genotypes can be caught, and experiments with a shuttle box showed that the preferred temperature of HbI-1 and HbI-2 was 15.4 and 8.2 °C, respectively. When exposed to hypoxia the preferred temperature of HbI-1 cod changed from 15.4 to 9.8 °C, while the HbI-2 cod showed no effect. McFarland compared oxygen consumption of cod caught in Denmark with haemoglobin type HbI-1 and HbI-2, but found no significant difference, so it is still unknown why Greenland Atlantic cod have a higher metabolic rate.
doi:10.1016/j.cbpa.2008.04.579
SETE.17 Why hypoxic bradycardia in fishes? A. Farrell (University of British Columbia) Why do certain fish respond to environmental hypoxia with bradycardia whereas mammals respond with tachycardia? Equivocal results regarding a potential benefit to gill oxygen transfer open the door for the present analysis of potential benefits of hypoxic bradycardia to cardiac function. The potential benefits, which include improving contractility through a negative force frequency effect, reducing cardiac oxygen demand by improving mechanical efficiency, and improving cardiac oxygen delivery to trabecular and compact cardiac muscle, recognize the ability of the fish heart to considerably vary stroke volume and its reliance on oxygen contained invenous blood. Further insights to the benefits of hypoxic bradycardia are provided by the observations that anemic trout, Antarctic fish, anoxia-tolerant fishes and air breathing fishes do not display hypoxic bradycardia. Research support provided by NSERC Canada. doi:10.1016/j.cbpa.2008.04.580
SETE.18 Temperature tolerance and respiration in coral reef fishes G. Nilsson (University of Oslo) Abstract not available. doi:10.1016/j.cbpa.2008.04.581
SETE.19 Intra-specific variation in muscle fibre phenotype I.A. Johnston, I.P.G. Amaral, V.L.A. Vieira (University of St Andrews) The large increase in body size observed between larval and adult fish requires the continuous production of fast myotomal muscle fibres until around 40% of the maximum length. Subsequent growth in myotomal girth only involves fibre hypertrophy, although myotubes can still be produced to repair damage following injury. The optimal fibre number hypothesis provides a physiological explanation for changes in final fibre
S207
number (FFN) with body size and environment. The hypothesis envisages an optimal fibre number which minimises the energy costs of maintaining ionic homeostasis in the muscle (Johnston et al., 2003, 2006). This presentation will consider various tests of the optimal fibre number hypothesis in marine and anadromous fishes and examine the relative importance of selection and developmental plasticity in generating the observed variation in FFN between populations. Recent genomic approaches to investigate the control of fibre number and experiments to determine the consequences of intraspecific variation in FFN for whole animal performance will be discussed. Johnston, I.A., Fernandez, D., Calvo, J., Vieira, V.L.A., North, T.W., Abercromby, M., and Garland, T. Jr. (2003). Reduction in muscle fibre number during the adaptive radiation of Notothenioid fishes: a phylogenetic perspective. J. Exp. Biol. 206, 25952609. Johnston, I.A., Abercromby, M., and Andersen, Ø. (2006). Muscle fibre number varies with haemoglobin phenotype in Atlantic cod as predicted by the optimal fibre number hypothesis. Biol. Lett. 2, 590592. doi:10.1016/j.cbpa.2008.04.582
SETE.20 Haemoglobin polymorphism and red blood cell sickling in marine fishes M. Berenbrink (University of Liverpool); D. McDonald (University of Miami); P. Koldkjaer (University of Liverpool)
In human sickle cell disease a single surface amino acid mutation in the beta globin chain leads to the formation of large insoluble haemoglobin (Hb) aggregates at low oxygen tension. This may cause peculiar cell deformations or ‘sickling’, which can cause vascular occlusion, organ failure and death. In a classic example of balanced polymorphism, the frequency of the mutated beta-globin allele is kept elevated in certain human populations because of the benefits for heterozygote carriers against infection with malaria parasites. In vitro, red blood cell sickling is also found in several marine fish species such as the oyster toadfish, Atlantic cod and other codfishes (Harison et al., 1998). Recently, we have demonstrated its occurrence in vivo in whiting, Merlangus merlangius, and suggested that it may be involved in protection against parasite infection (Koldkjaer and Berenbrink, 2007). However, the molecular and genetic bases of sickling in marine fishes are poorly understood. Here we describe large intraspecific differences in red blood cell sickling in the Gulf toadfish Opsanus beta, which are associated with a complex Hb polymorphism. In contrast, we show that in Atlantic cod nearly 100% sickling can be induced in all Hb genotypes that comprise the well-known HbI polymorphism. These results indicate distinct intra and interspecific differences in red blood cell sickling in marine fishes, although its relative costs and benefits remain to be established. References Harosi, et al., 1998. Biol. Bull. 195, 5–11. Koldkjaer, Berenbrink, 2007. J. Exp. Biol. 210, 3451–3460. doi:10.1016/j.cbpa.2008.04.583