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The impact of early rearing environment on phenotypic development in teleosts has been reasonably well-documented, but only recently has attention been paid to sturgeon raised for conservation purposes. In the present study, we hypothesized that rearing environment will result in the development of distinct metabolic phenotypes in age-0 lake sturgeon (Acipenserfulvescens) and that these phenotypes will drive differential survival rates during a simulated overwintering event. Lake sturgeon gametes were fertilized and raised in one of three different environments: 16[degrees]C +100% dissolved oxygen (DO), 14[degrees]C + 100% DO, and 16[degrees]C + 80% DO, each with or without substrate. We measured standard metabolic rate, forced maximum metabolic rate, metabolic scope, energy density, hepatosomatic index, Fulton's condition factor, and enzyme activities associated with ATP production. Our results suggest that subtle changes in abiotic environments during early life history result in the development of distinct metabolic phenotypes during the first year of life. These have important implications for survival of age-0 lake sturgeon when stocked in the fall of their first year. Si l'incidence du milieu de grossissement precoce sur le developpement phenotypique chez les teleosteens est raisonnablement bien documentee, ce n'est que recemment qu'une attention a ete portee aux esturgeons eleves a des fins de conservation. Nous avons postule que differents milieux de grossissement se traduiraient par le developpement de differents phenotypes metaboliques chez les esturgeons jaunes (Acipenserfulvescens) de 0 an et que ces phenotypes produiraient des taux de survie differents durantun episode d'hivernage simule. Des gametes d'esturgeon jaune ont ete fertilises et eleves dans l'un des trois milieux suivants: 16[degrees]C +100 % d'oxygene dissous (OD), 14[degrees]C +100 % OD et 16[degrees]C + 80 % OD, avec ou sans substrat. Nous avons mesure le metabolisme standard, le metabolisme maximum force, la portee metabolique, la densite energetique, l'indice hepatosomatique, le coefficient de condition de Fulton et des activites enzymatiques associees a la production d'ATP. Nos resultats portent a croire que de petites variations du milieu abiotique au debut du cycle biologique se traduisent par le developpement de phenotypes metaboliques distincts durant la premiere annee de vie. Ces differents phenotypes ont une importante incidence sur la survie des esturgeons jaunes de 0 an ensemences a l'automne de leur premiere annee. [Traduit par la Redaction], Introduction Conservation aquaculture is a common approach used towards improving the status of fish populations at risk. Much investment has been made in this area in association with conservation efforts [...]

Understanding how metabolic costs change in relation to increasing temperature under future climate changes is important to predict how ectotherms will be affected across the globe. In fish, whole body respiration is traditionally used to estimate aerobic performance via an organism's minimum and maximum oxygen consumption rates. However, mitochondria play a crucial role in the aerobic cascade and may be a useful surrogate of aerobic performance. To test whether whole body oxygen consumption and mitochondrial capacity are correlated, we estimated whole body metabolic and mitochondrial respiration rates (using permeabilized red muscle fibres) in brook trout (Salvelinus fontinalis (Mitchill, 1814)) at 10, 15, and 20 °C. Standard metabolic rate increased with acclimation temperature, while maximum rates were less sensitive. All mitochondrial respiration rates increased with acclimation temperature, suggesting that red muscle mitochondrial preparations may correlate to the minimal metabolic demands in this species. When expressed as relative rates of electron flow, the red muscle fibres showed no effect of temperature on mitochondrial coupling efficiency. However, there was a pattern of declining capacity to augment respiration via complex II with increasing temperature with a concomitant increase in the capacity of the phosphorylating system relative to maximal rates of mitochondrial electron flow. [ABSTRACT FROM AUTHOR]

Homeostatic regulation allows organisms to secure basic physiological processes in a varying environment. To counteract fluctuations in ambient carbonate system speciation due to elevated seawater pC[O.sub.2] (hypercapnia), many aquatic crustaceans excrete/accumulate acid-base equivalents through their gills; however, not much is known about the role of ammonia in this response. The present study investigated the effects of hypercapnia on acid-base and ammonia regulation in the Dungeness crab, Metacarcinus magister on the whole animal and isolated gill levels. Hemolymph pC[O.sub.2] and [HC[O.sub.3.sup.-]] increased in M. magister acclimated to elevated pC[O.sub.2] (330 Pa), while pH remained stable. Additionally, hemolymph [[Na.sup.+]], [[Ca.sup.2+]], and [S[O.sub.4.sup.2-]] were significantly increased. When challenged with varying pH during gill perfusion, the pH of the artificial hemolymph remained relatively unchanged. Overall, ammonia production and excretion, as well as oxygen consumption, were reduced in crabs acclimated to elevated pC[O.sub.2], demonstrating that either (amino acid) oxidation is reduced in response to this particular stress, or nitrogenous wastes are excreted in an alternative form., Introduction In many marine organisms, a rise in seawater pC[O.sub.2] (environmental hypercapnia) causes an increase in body fluid pC[O.sub.2] in order to maintain an outwardly directed gradient for the passive [...]

The hyperinsulism/hyperammonemia (HI/HA) syndrome is caused by glutamate dehydrogenase (GDH) gain-of-function mutations that reduce the inhibition by GTP, consequently increasing the activity of GDH in vivo. The source of the hyperammonemia in the HI/HA syndrome remains unclear. We examined the effect of systemic activation of GDH on ammonia metabolism in the rat. 2-Aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) is a nonmetabolizable analog of the natural GDH allosteric activator leucine. A dose of 100 [micro]mol BCH/100 g rat resulted in a mild systemic hyperammonemia. Using arterial-venous (A-V) differences, we exclude the liver, intestine, and skeletal muscle as major contributors to this BCH-induced hyperammonemia. How ever, renal ammonia output increased, as demonstrated by an increase in A-V difference for ammonia across the kidney in BCH-treated animals. Isolated renal cortical tubules incubated with BCH increased the rate of ammoniagenesis from glutamine by 40%. The flux through GDH increased more than twofold when BCH was added to renal mitochondria respiring on glutamine. The flux through glutaminase was not affected by BCH, whereas glutamate-oxaloacetate transaminase flux decreased when normalized to glutaminase flux. These data show that increased renal ammoniagenesis due to activation of GDH can explain the BCH-induced hyperammonemia. These results are discussed in relation to the organ source of the ammonia in the HI/HA syndrome as well as the role of GDH in regulating renal ammoniagenesis. kidney; mitochondria; glutaminase; 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid doi: 10.1152/ajpendo.00028.2010.

Trimethylamine oxide (TMAO) is typically accumulated as an organic osmolyte in marine elasmobranchs to levels second only to urea (which can reach >400 mM); however, little is known about the whole animal regulation of TMAO in elasmobranchs. In the present study on the winter skate (Leucoraja ocellata), we determine whether this species can maintain levels of TMAO in the absence of feeding, and if so, is this due to endogenous synthesis or low whole animal losses. Winter skates maintain plasma TMAO levels for up to 45 days without feeding. The liver displays methimazole oxidation, which is consistent with the presence of flavin-containing monooxygenase (E.C. 1.14.13.8) activity, the class of enzymes responsible for the physiological oxygenation of trimethylamine (TMA) to TMAO in mammals. However, no evidence for TMA oxygenation by winter skates was found using in vivo or in vitro techniques, indicating no significant capacity for endogenous TMAO synthesis. Fed skates displayed low, but measurable (~4-13 [micro]mol * [kg.sup.-1] * [h.sup.-1]), efflux of TMAO (plus TMA), whereas fasted skates did not. Using the loss of injected [[sup.14]C]TMAO, it was determined that whole animal TMAO losses are likely elasmobranch; excretion; flavin-containing monooxygenase; trimethylamine oxide synthesis

Atlantic cod (Gadus morhua) were held either at seasonal ambient temperatures (-0.3 to 11[degrees]C) or at a relatively constant control temperature (8-11[degrees]C) to investigate aspects of protein synthesis during a period of compensatory growth. Protein synthesis rate, total RNA, and RNA-specific protein synthesis rate were determined in white muscle and liver when ambient temperatures were -0.3. 4.5, and 11[degrees]C in February, June, and July, respectively. To allow for comparisons between treatment temperatures, fish were also acutely transferred to a comparable assay temperature in February and June. Over the transition from 4.5 to 11[degrees]C (June to July), the ambient-held cod had a significant increase in size and a substantially higher growth rate relative to control-held fish over the same period, consistent with cold-induced compensatory growth. During the onset of this enhanced growth, in June when ambient temperature was ~4.5[degrees]C, ambient-held fish elevated their capacity for protein synthesis in the white muscle and liver via elevation of the RNA content. When ambient temperature reached the same point as for the control fish (11[degrees]C), the rate of white muscle protein synthesis remained higher in the ambient-held vs. that in the control-held fish, a process facilitated by elevated RNA content and greater RNA-specific rate of protein synthesis. In the liver, all measured characteristics of protein synthesis were the same for ambient and control fish in July. The latter suggests that compensatory growth may be in part explained by improved efficiency of protein synthesis. efficiency of protein synthesis; cold adaptation; muscle; liver

Differences in genomic architecture between populations, such as chromosomal inversions, may play an important role in facilitating adaptation despite opportunities for gene flow. One system where chromosomal inversions may be important for eco‐evolutionary dynamics is in freshwater fishes, which often live in heterogenous environments characterized by varying levels of connectivity and varying opportunities for gene flow. In the present study, reduced representation sequencing was used to study possible adaptation in n = 345 walleye (Sander vitreus) from three North American waterbodies: Cedar Bluff Reservoir (Kansas, USA), Lake Manitoba (Manitoba, Canada), and Lake Winnipeg (Manitoba, Canada). Haplotype and outlier‐based tests revealed a putative chromosomal inversion that contained three expressed genes and was nearly fixed in walleye assigned to Lake Winnipeg. These patterns exist despite the potential for high gene flow between these proximate Canadian lakes, suggesting that the inversion may be important for facilitating adaptive divergence between the two lakes despite gene flow. However, a specific adaptive role for the putative inversion could not be tested with the present data. Our study illuminates the importance of genomic architecture consistent with local adaptation in freshwater fishes. Furthermore, our results provide additional evidence that inversions may facilitate local adaptation in many organisms that inhabit connected but heterogenous environments. [ABSTRACT FROM AUTHOR]

Senescence—the deterioration of functionality with age—varies widely across taxa in pattern and rate. Insights into why and how this variation occurs are hindered by the predominance of laboratory-focused research on short-lived model species with determinate growth. We synthesize evolutionary theories of senescence, highlight key information gaps and clarify predictions for species with low mortality and variable degrees of indeterminate growth. Lake trout are an ideal species to evaluate predictions in the wild. We monitored individual males from two populations (1976–2017) longitudinally for changes in adult mortality (actuarial senescence) and body condition (proxy for energy balance). A cross-sectional approach (2017) compared young (ages 4–10 years) and old (18–37 years) adults for (i) phenotypic performance in body condition, and semen quality—which is related to fertility under sperm competition (reproductive senescence)—and (ii) relative telomere length (potential proxy for cellular senescence). Adult growth in these particular populations is constrained by a simplified foodweb, and our data support predictions of negligible senescence when maximum size is only slightly larger than maturation size. Negative senescence (aka reverse senescence) may occur in other lake trout populations where diet shifts allow maximum sizes to greatly exceed maturation size. [ABSTRACT FROM AUTHOR]

Urban wildlife populations experience human-driven environmental changes that can be both beneficial and detrimental to individual health. We measured body condition and serum chemistry (electrolyte levels, markers of kidney and liver function, protein, glucose, and cholesterol) in a native urban and rural population of Eastern Gray Squirrel (Sciurus carolinensis) to assess whether we could detect physiological responses to environmental stressors or dietary differences. We found no differences in body condition between habitats and no evidence of malnutrition at either site. However, urban squirrels had higher blood glucose, lower potassium, phosphorus, chloride, and albumin:globulin ratios. These results align with previous findings of increased dietary sugar in cities and suggest that urban populations of gray squirrels are under greater environmental stress than rural populations, providing future directions for studying physiological responses to urbanization. [ABSTRACT FROM AUTHOR]