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William R Driedzic - One of the best experts on this subject based on the ideXlab platform.

  • cloning and characterization of aquaglyceroporin genes from rainbow smelt Osmerus Mordax and transcript expression in response to cold temperature
    Comparative Biochemistry and Physiology B, 2015
    Co-Authors: Jennifer R Hall, Kathy A Clow, Matthew L Rise, William R Driedzic
    Abstract:

    Abstract Aquaglyceroporins (GLPs) are integral membrane proteins that facilitate passive movement of water, glycerol and urea across cellular membranes. In this study, GLP-encoding genes were characterized in rainbow smelt ( Osmerus Mordax Mordax ), an anadromous teleost that accumulates high glycerol and modest urea levels in plasma and tissues as an adaptive cryoprotectant mechanism in sub-zero temperatures. We report the gene and promoter sequences for two aqp10b paralogs ( aqp10ba , aqp10bb ) that are 82% identical at the predicted amino acid level, and aqp9b . Aqp10bb and aqp9b have the 6 exon structure common to vertebrate GLPs. Aqp10ba has 8 exons; there are two additional exons at the 5′ end, and the promoter sequence is different from aqp10bb . Molecular phylogenetic analysis suggests that the aqp10b paralogs arose from a gene duplication event specific to the smelt lineage. Smelt GLP transcripts are ubiquitously expressed; however, aqp10ba transcripts were highest in kidney, aqp10bb transcripts were highest in kidney, intestine, pyloric caeca and brain, and aqp9b transcripts were highest in spleen, liver, red blood cells and kidney. In cold-temperature challenge experiments, plasma glycerol and urea levels were significantly higher in cold- compared to warm-acclimated smelt; however, GLP transcript levels were generally either significantly lower or remained constant. The exception was significantly higher aqp10ba transcript levels in kidney. High aqp10ba transcripts in smelt kidney that increase significantly in response to cold temperature in congruence with plasma urea suggest that this gene duplicate may have evolved to allow the re-absorption of urea to concomitantly conserve nitrogen and prevent freezing.

  • 1GLYCEROL PRODUCTION BY RAINBOW SMELT (Osmerus Mordax) AT SUB-ZERO TEMPERATURES IS DEPENDENT UPON BUT NOT CONTROLLED BY G3PDH ACTIVITY
    2014
    Co-Authors: William R Driedzic, C. Wilson E. Short
    Abstract:

    Rainbow smelt (Osmerus Mordax) is a teleost that tolerates temperatures close to the freezing point of sea water through the use of proteins (Ewart and Fletcher, 1990) and glycerol (Raymond, 1992) as antifreeze agents. The lower the temperature, the higher the glycerol level such that at –2°C serum glycerol may approach 400 mM (Raymond, 1992). Although effective at lowering the freezing temperature glycerol is lost at a rate that may exceed 10 % of glycerol stores per day (Raymond, 1993). Therefore, there must be vigorous glycerol synthesis at very low temperatures. Liver is an active site of glycerol synthesis and one source of carbon for glycerol is probably dietary amino acids that are degraded to glyceraldehyde 3-phosphate (G3P) (Raymond and Driedzic, 1997; Driedzic et al., 1998). It appears that carbon flow is G3P ® dihydroxyacetone-P (DHAP) ® glycerol-3-P ® glycerol. Blood glycerol levels and liver enzyme activity levels were determined in rainbow smelt, Atlantic tomcod (Microgadus tomcod) and smooth flounder (Liposetta putmani). All animals were sampled simultaneously from sub-zer

  • © 2011 Molecular Vision
    2013
    Co-Authors: Connie E Short, Kathy A Clow, William R Driedzic
    Abstract:

    Osmotic pressure-adaptive responses in the eye tissues of rainbow smelt (Osmerus Mordax

  • glycerol uptake is by passive diffusion in the heart but by facilitated transport in rbcs at high glycerol levels in cold acclimated rainbow smelt Osmerus Mordax
    American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2012
    Co-Authors: Kathy A Clow, William R Driedzic
    Abstract:

    Rainbow smelt (Osmerus Mordax) is a small fish that accumulates glycerol at low winter seawater temperatures. In laboratory-held fish, glycerol concentration typically reaches 225 mM in plasma and ...

  • expression analysis of glycerol synthesis related liver transcripts in rainbow smelt Osmerus Mordax exposed to a controlled decrease in temperature
    Physiological and Biochemical Zoology, 2012
    Co-Authors: Jennifer R Hall, Matthew L Rise, Connie E Short, William R Driedzic
    Abstract:

    AbstractRainbow smelt (Osmerus Mordax) accumulate high glycerol levels to avoid freezing at subzero temperatures. Glyceroneogenesis is activated by low temperature and occurs in liver via a branch in glycolysis and gluconeogenesis. In this study, carbohydrate and liver transcript levels of 21 genes potentially associated with glycerol production were assessed during a controlled warm to cold transition. Smelt were held at 8°C (warm smelt; non–glycerol accumulating) or subjected to a controlled decrease in water temperature from 8° to 0°C (cold smelt; glycerol accumulating) and sampled at the end of the temperature decrease and 1 mo later. In cold smelt compared with warm smelt, liver glycogen levels were lower and phosphoglucomutase transcript levels were higher. Plasma glycerol levels were higher and increased over time in cold smelt; in cold smelt, liver phosphofructokinase and pyruvate dehydrogenase kinase transcript levels increased over time. These findings imply that glycerol production is being fue...

Julian J. Dodson - One of the best experts on this subject based on the ideXlab platform.

  • Smelt AFLP data - Dodson et al. 2015 (PlosONE)
    2016
    Co-Authors: Julian J. Dodson, Mariefrance Barrette, Gaetan Daigle, Audrey Bourret, Julie Turgeon, Frederic Lecomte
    Abstract:

    This file contains AFLP genotypes (29 loci) for 447 Rainbow smelt (Osmerus Mordax). One sheet contains the data, one sheet establishes the correspondence between Site numbers in the publication (Table 2 and Figure 2) and codes used for indiividual genotypes

  • intraspecific vicariant history and the evolution of adaptive morphological diversity in a fish species Osmerus Mordax
    Biological Journal of The Linnean Society, 2009
    Co-Authors: Mariefrance Barrette, Gaetan Daigle, Julian J. Dodson
    Abstract:

    Vicariant geographic isolation and resource partitioning have long been independently identified as processes contributing to the morphological divergence of closely-related species. However, little is known about the extent to which vicariant history influences the adaptive ecological divergence associated with resource partitioning and trophic specialization within species. The present study thus quantified the contribution of vicariant historical genetic divergence to the adaptive contemporary morphological divergence of intraspecific feeding specialists in the Rainbow smelt (Pisces: Osmerus Mordax). This species is characterized by the polyphyletic origin of two lacustrine feeding specialists originating in two intraspecific lineages associated with independent glacial refuges. The historical genetic segregation was initiated approximately 350 000 years ago, whereas the lacustrine trophic segregation arose within the past 10 000 years. Wild caught lacustrine smelt populations were grouped a priori based on known historical genetic identities (Acadian and Atlantic mitochondrial DNA clades) and contemporary feeding specializations (microphageous and macrophageous morphotypes). The present study demonstrated that independent suites of correlated morphological traits are associated with either vicariant history or contemporary feeding specializations. Second, functionally-similar feeding specialists exhibit distinct morphologies resulting largely from vicariant historical processes. Although, the evolutionary processes producing historical phenotypes remains unknown, the results obtained demonstrate how adaptive radiation associated with ecological resource partitioning and feeding specializations can be strongly influenced by intraspecific phenotypic diversification resulting from relatively recent vicariant histories. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 140–151.

  • cestode parasitism as a regulator of early life history survival in an estuarine population of rainbow smelt Osmerus Mordax
    Marine Ecology Progress Series, 2006
    Co-Authors: Jeanfrancois Bourque, Julian J. Dodson, Daniel A J Ryan, David J. Marcogliese
    Abstract:

    In the St. Lawrence middle estuary, the larvae and juveniles of rainbow smelt Osmerus Mordax are infected with intestinal parasites (the cestode Proteocephalus tetrastomus). Such para- sitism is suspected to impair growth rate, which may in turn influence the ability of smelt to migrate vertically and to be retained in the estuarine turbidity maximum (ETM), the nursery area of this population. We hypothesised that parasitism contributes to size-selective mortality by altering patterns of vertical migration, thus contributing to transport losses from the nursery area. Parasitism was found to affect growth rate, as determined by otolith microstructure analysis, and to contribute to mortality. Larvae which survived the parasitic infection were found to be, on average, larger than the uninfected survivors at some point in their early life history prior to infection. Significant size- selective mortality was observed among infected larvae relative to uninfected larvae. There was, however, no significant difference in the vertical distribution of parasitised versus non-parasitised larvae, indicating that size-selective mortality was not due to transport losses from the nursery area. Rather, starvation or predation was most likely responsible for observed mortality patterns. We illustrate that variability in the incidence of parasitic infection among years may form the basis for variability in recruitment and the abundance of the adult smelt population.

  • Occurrence of Proteocephalus tetrastomus (Rudolphi, 1810) (Cestoda: Proteocephalidea) in Larval Rainbow Smelt (Osmerus Mordax) in North America: Identification of a Potential Pathogen Confirmed
    The Journal of parasitology, 2004
    Co-Authors: Tomáš Scholz, David J. Marcogliese, J-f. Bourque, Andrea Škeříková, Julian J. Dodson
    Abstract:

    A morphological evaluation and genetic analysis (sequencing of ITS2 region of rDNA) of proteocephalidean cestodes from rainbow smelt (Osmerus Mordax) in the Saint Lawrence Estuary, Canada, has shown their conspecificity with Proteocephalus tetrastomus, a specific parasite of smelt (Osmeridae), previously known only from northern Europe, Russia, and Japan. The parasite occurs only in larval, but not adult, smelt in the Saint Lawrence Estuary. Prevalence of larval smelt infection was 42% (n = 50), mean intensity 2.1 ± 2.4 and mean abundance 1.1 ± 1.0.

  • climate change and abundance cycles of two sympatric populations of smelt Osmerus Mordax in the middle estuary of the st lawrence river canada
    Canadian Journal of Fisheries and Aquatic Sciences, 2001
    Co-Authors: Marc Mingelbier, Frederic Lecomte, Julian J. Dodson
    Abstract:

    Commercial catches of two ecologically distinct sympatric smelt (Osmerus Mordax) populations segregated along the two shores of the St. Lawrence middle estuary exhibited inverse patterns with periodicities on the order of 30 years. The influence of water level in the St. Lawrence River and air temperature, chosen to reflect variations in hydrology and climate, differed markedly between the two populations. Analyses revealed that both water level and temperature were generally positively related with north-shore smelt landings and negatively related with south-shore smelt landings. For both populations, a number of significant climatic factors contributing to variance in smelt landings were lagged by one to three years relative to the year of landings, indicating that climatic variables influenced smelt recruitment. The contrasting role of hydroclimatic variables in driving these abundance cycles is likely related to differential exploitation of estuarine habitats; the south-shore population is associated ...

Louis Bernatchez - One of the best experts on this subject based on the ideXlab platform.

  • the rainbow smelt Osmerus Mordax complex of lake utopia threatened or misunderstood
    Environmental Biology of Fishes, 2004
    Co-Authors: Allen R Curry, Steve L Currie, Louis Bernatchez, Robert Saintlaurent
    Abstract:

    We report on the spawning ecology, genetic characteristics, and predation threats to spawning groups of rainbow smelt, Osmerus Mordax, in Lake Utopia, New Brunswick where a dwarf morpho-type has been listed as a threat- ened species. Two spawning groups in three inlet streams had been previously identified; we observed three groups using four inlet streams. The earliest group was the largest in body size (12–29 cm fork length (FL)), lowest in numbers (∼1 000), and completed spawning approximately two weeks before the second group. The early spawners were previously identified as the normal morpho-type, but we now classify these as a giant morphotype. The second group spawned in three different streams. They were intermediate in body size (10–15 cm FL) and numbers (∼10 000). The dwarf group began spawning as the intermediate group completed spawning and within the same three streams. The dwarfs were numerous (∼1 000 000), small in size (<12 cm), and with higher gill raker counts. Microsatellite analyses suggested that gene flow among groups occurred, but genetic diver- gence was high and genetic separation among populations of the same group among streams and within a stream occurred. Stable isotopes and stomach contents indicated the dwarf group were likely consumed by a variety of fishes, but they were not the sole food resource of any predator including a population of landlocked salmon. These are some of the complexities of smelt ecology, but there are clearly life history tactics that we do not yet understand.

  • divergent selection maintains adaptive differentiation despite high gene flow between sympatric rainbow smelt ecotypes Osmerus Mordax mitchill
    Molecular Ecology, 2003
    Co-Authors: Robert Saintlaurent, Michel Legault, Louis Bernatchez
    Abstract:

    In this study, we investigate the relative role of historical factors and evolutionary forces in promoting population differentiation in a new case of sympatric dwarf and normal ecotypes of the rainbow smelt (Osmerus Mordax Mitchill) in Lac Saint-Jean (Quebec, Canada). Our first objective was to test the hypothesis that the evolution of sympatric smelt ecotypes in Lac Saint-Jean has been contingent upon the secondary contact between two evolutionary lineages in postglacial times. Secondly, the QST method was applied to test the null hypothesis that the extent of phenotypic differences relative to that of neutral marker variation would be similar in comparisons involving populations within and among ecotypes. Thirdly, we applied a quantitative-genetic method as an exploratory assessment as to whether the amount of gene flow observed between populations could affect divergence in adaptive traits under specific conditions. This study revealed a unique situation of dwarf and normal smelt ecotypes that are, respectively, characterized by selmiparous and iteroparous life histories and the occurrence in each of two genetically distinct populations that synchronously use the same spawning habitat in two tributaries. Historical contingency has apparently played little role in the origin of these populations. In contrast, an important role of divergent natural selection in driving their phenotypic divergence was suggested. While divergent selection has apparently been strong enough to maintain phenotypic differentiation in the face of migration, this study suggests that gene flow has been sufficiently important to modulate the extent of adaptive differentiation being achieved between ecotypes, unless the extent of stabilizing selection acting on smelt ecotypes is much more pronounced than usually reported in natural populations.

  • a mtdna analysis of spatiotemporal distribution of two sympatric larval populations of rainbow smelt Osmerus Mordax in the st lawrence river estuary quebec canada
    Canadian Journal of Fisheries and Aquatic Sciences, 1998
    Co-Authors: Dany Pigeon, Julian J. Dodson, Louis Bernatchez
    Abstract:

    Ecological isolation through resource partitioning is invoked as a major factor for explaining the persistence of genetically distinct yet closely related sympatric populations. Two genetically distinct sympatric populations of anadromous rainbow smelt (Osmerus Mordax) exist in the middle estuary of the St. Lawrence River. The persistence of these coexisting populations in sympatry is in conflict with current theoretical concepts predicting population richness. In the present study, we performed mtDNA PCRnRFLP analysis of 922 larvae from 33 sampling stations to test the hypothesis that the larvae belonging to the two sympatric smelt populations of the St. Lawrence middle estuary are spatially segregated and that such segregation may promote the persistence of the populations. Results clearly revealed spatial homogeneity in the relative distribution of larvae from the two populations. Consequently, they did not support our working hypothesis that larvae belonging to the two sympatric smelt populations are spatially segregated. Two alternative explanations may account for the lack of spatial partitioning observed here. Competition may not be important enough to promote resource partitioning at the larval stage. Alternatively, resource partitioning occurs, but not spatially. This study also demonstrated that the effect of historical events may have been as important as contemporary ecological settings in determining genetic population structure in smelt. Resume : Plusieurs auteurs suggrent que le partage des ressources Ocologiques est le principal facteur permettant le maintien de populations en sympatrie. Des travaux rOcents ont dOmontrO liexistence de deux populations sympatriques diOperlans arc-en-ciel (Osmerus Mordax) anadromes gOnOtiquement distinctes mais ayant le potentiel de sihybrider dans liestuaire moyen du St-Laurent. La persistance de populations en sympatrie dans ce milieu est contraire aux prOdictions thOoriques de lihypothse du « membernvagrant ». Dans cette Otude, nous avons effectuO une analyse de PCRnRFLP sur liADNmt de 922 larves diOperlans reprOsentant 33 sites diOchantillonnage dans le but de tester lihypothse voulant que ces deux populations larvaires soient spatio-temporellement sOgrOgOes et que cette sOgrOgation explique en partie leur persistance dans le milieu. Les rOsultats de ces analyses dOmontrent une homogOnOitO spatiale dans la distribution des larves appartenant aux deux populations. ConsOquemment, ces rOsultats ne supportent pas lihypothse de dOpart. On peut expliquer ces rOsultats de deux faAons diffOrentes. Premirement, le partage des ressources est peu important au niveau larvaire pour liOperlan du St-Laurent. Alternativement, le partage des ressources est significatif, mais ne se fait pas spatialement. Ces rOsultats dOmontrent de plus que les effets des OvOnements historiques sur la structure des populations peuvent, dans certaines circonstances, Œtre plus importants que les OvOnements Ocologiques contemporains.

  • mitochondrial dna analysis confirms the existence of two glacial races of rainbow smelt Osmerus Mordax and their reproductive isolation in the st lawrence river estuary quebec canada
    Molecular Ecology, 1997
    Co-Authors: Louis Bernatchez
    Abstract:

    A phylogeographic analysis of mitochondrial DNA variation was performed in order to test the hypothesis that north-eastern North America has been postglacially recolonized by two races of rainbow smelt Osmerus Mordax. This was accomplished by documenting the geographical distribution of two major mtDNA phylogenetic clades among 1290 smelt from 49 lacustrine and anadromous populations covering most of the species’ native range. The data set was built by combining previously published results with those generated in this study. The two mtDNA clades showed a geographical dichotomy, independent of life-history types, whereby the more eastern populations were either fixed or largely dominated by one clade and western populations for the other. Such geographical pattern implying a phylogenetic discontinuity provided strong evidence for the persistence of smelt in two distinct glacial refugia as well as their differential postglacial dispersal. The most likely refugium for the so-called Atlantic race was the Atlantic coastal plains, whereas that of the so-called Acadian race was the exundated Grand Banks area. Patterns of postglacial dispersal interpreted from palaeogeographic events suggested that the Atlantic race recolonized northern regions about 5000 years prior the Acadian race. Both races came into contact in the St Lawrence River estuary. While gene flow has been possible, the sympatric occurrence in the estuary of anadromous populations alternatively dominated by one mtDNA clade or the other indicated that reproductive isolation mechanisms between the two races developed within this contact zone. This represents the first evidence of secondary intergradation among distinct races of aquatic organisms in an estuarine environment.

Vanya K Ewart - One of the best experts on this subject based on the ideXlab platform.

  • molecular analysis tissue profiles and seasonal patterns of cytosolic and mitochondrial gpdh in freeze resistant rainbow smelt Osmerus Mordax
    Physiological and Biochemical Zoology, 2011
    Co-Authors: Jason L Robinson, Vanya K Ewart, Jennifer R Hall, Mark Charman, William R Driedzic
    Abstract:

    AbstractRainbow smelt (Osmerus Mordax) is an anadromous teleost that, beginning in late fall, accumulates plasma glycerol in excess of 200 mM, which subsequently decreases in the spring. The activity of cytosolic glycerol-3-phosphate dehydrogenase (cGPDH) is higher (i) in liver of smelt than in that of Atlantic salmon and capelin (nonglycerol accumulators), (ii) in liver of smelt maintained at 1°C than in that of smelt held at 8°–10°C, and (iii) in smelt liver than in smelt muscle, heart, brain, or kidney. In addition, transcript levels of cGPDH in liver peak in December during the onset of glycerol production and then decline over the remainder of the season. There are four cGPDH protein isoforms in smelt liver that are present regardless of glycerol production status. A minimum of four cGPDH gene copies identified by Southern blotting provide adequate genetic potential to yield multiple protein isoforms. A full-length cDNA for smelt mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) was cloned and...

  • seasonal expressed sequence tags of rainbow smelt Osmerus Mordax revealed by subtractive hybridization and the identification of two genes up regulated during winter
    Gene, 2008
    Co-Authors: Robert C Richards, William R Driedzic, Connie E Short, John C Achenbach, Jennifer Kimball, Michael E Reith, Vanya K Ewart
    Abstract:

    The rainbow smelt (Osmerus Mordax) is freeze-resistant and maintains swimming and feeding activity during winter. In order to identify genes differentially expressed in smelt liver response to winter water temperatures, a large-scale analysis of gene expression using suppression subtractive hybridization was carried out using samples obtained in fall and winter. Forward and reverse subtractions were performed, subtraction-enriched products were cloned, and clones were sequenced from both of the resulting libraries. When 27 of these genes were screened by semi-quantitative RT-PCR to identify candidates for differential expression based generally on 2-fold changes in expression, one encoding FK506-binding protein 5 was classified as up-regulated in response to seasonal change, another encoding the mitochondrial solute carrier 25 member 25 (ATP-Mg/Pi carrier) was similarly classified with seasonal change and low temperature shift, and the one encoding the 78 kDa glucose-regulated protein was provisionally classified as down-regulated with low temperature shift. Analysis of fall (warm) and winter (cold) seasonal samples by quantitative PCR (qPCR) revealed significant up-regulation of genes encoding FK506-binding protein 51 and the mitochondrial solute carrier, whereas the gene encoding the glucose-regulated protein showed no significant change in expression. The mitochondrial solute carrier and FK506-binding protein results may relate to changes in cortisol action, as both are regulated by cortisol in other species.

  • low temperature directly activates the initial glycerol antifreeze response in isolated rainbow smelt Osmerus Mordax liver cells
    American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2008
    Co-Authors: Kathy A Clow, Vanya K Ewart, William R Driedzic
    Abstract:

    Rainbow smelt (Osmerus Mordax) accumulate high levels of glycerol in winter that serve as an antifreeze. Liver glycogen is a source of glycerol during the early stages of glycerol accumulation, whe...

  • accelerated hepatic glycerol synthesis in rainbow smelt Osmerus Mordax is fuelled directly by glucose and alanine a 1h and 13c nuclear magnetic resonance study
    Journal of Experimental Zoology Part A: Comparative Experimental Biology, 2006
    Co-Authors: John A Walter, Vanya K Ewart, Connie E Short, Ian W Burton, William R Driedzic
    Abstract:

    At seawater temperatures below 1 degrees C, rainbow smelt (Osmerus Mordax) accumulate plasma levels of glycerol up to 400 mM. Aspects of the synthesis of glycerol in liver and its regulation were previously investigated, but the pathways leading to glycerol synthesis remained unconfirmed. Here, we report nuclear magnetic resonance (NMR) studies which elucidate, in more detail, the fuel sources for rapid glycerol synthesis in rainbow smelt. Initial NMR analysis of liver homogenates from fish held at cold (-1 degrees C) temperatures and from fish transferred from 8 degrees C to -1 degrees C showed elevated glycerol, whereas those from fish held at 8 degrees C had far lower glycerol levels. These results confirm a temperature-responsive glycerol synthesis and show that NMR is a suitable approach to investigate the phenomenon. Further studies with fish held at low temperature and injected with labelled L-[2,3-(13)C(2)] alanine or D-[U-(13)C(6)]glucose revealed conversion of both alanine and glucose to glycerol. (13)C spectra showed satellites ((1)J(CC)=41.1 Hz) about the glycerol resonances indicating intact incorporation of a (13)C-(13)C unit in liver glycerol of fish injected with L-[2,3-(13)C(2)]alanine and a (13)C-(13)C-(13)C unit in liver glycerol of fish injected with D[U-(13)C(6)]glucose. Thus, glycerol can be efficiently produced directly from amino acid precursors by glyceroneogenesis, which is an abbreviated gluconeogenesis process leading to glycerol through dihydroxyacetone phosphate (DHAP). Glucose can also be metabolised to glycerol via an abbreviated form of glycolysis that similarly leads to glycerol through DHAP.

  • glycerol production in rainbow smelt Osmerus Mordax may be triggered by low temperature alone and is associated with the activation of glycerol 3 phosphate dehydrogenase and glycerol 3 phosphatase
    The Journal of Experimental Biology, 2006
    Co-Authors: William R Driedzic, Kathy A Clow, Connie E Short, Vanya K Ewart
    Abstract:

    Rainbow smelt (Osmerus Mordax) accumulate high levels of glycerol in winter that serves as an antifreeze. Fish were subjected to controlled decreases in water temperature and levels of plasma glycerol, liver metabolites and liver enzymes were determined in order to identify control mechanisms for the initiation of glycerol synthesis. In two separate experiments, decreases in temperature from 8°C to 0°C over a period of 10‐11·days resulted in increases in plasma glycerol from levels of less than 4·mmol·l ‐1 to approximate mean levels of 40 (first experiment) and 150·mmol·l ‐1 (second experiment). In a third experiment, decreases in temperature to ‐1°C resulted in plasma glycerol levels approaching 500·mmol·l ‐1 . The accumulation of glycerol could be driven in either December or March, thus eliminating decreasing photoperiod as a necessary cue for glycerol accumulation. Glycerol accumulation in plasma was associated with changes in metabolites in liver leading to increases in the mass action ratio across the reactions catalyzed by glycerol-3-phosphate dehydrogenase (GPDH) and glycerol-3-phosphatase (G3Pase). The maximal, in vitro activity of GPDH, increased twofold in association with a sharp increase in plasma glycerol level. The metabolite levels and enzyme activities provide complementary evidence that GPDH is a regulatory site in the low temperature triggered synthesis of glycerol. Indirect evidence, based on calculated rates of in vivo glycerol production by liver, suggests that G3Pase is a potential rate-limiting step. As well, transient increases in glyceraldehyde-3-phosphate dehydrogenase and alanine aminotransferase suggest that these sites are components of a suite of responses, in rainbow smelt liver, induced by low temperature.

Lars G. Rudstam - One of the best experts on this subject based on the ideXlab platform.

  • Early mortality and freshwater forage fish recruitment: nonnative alewife and native rainbow smelt interactions in Lake Champlain
    Canadian Journal of Fisheries and Aquatic Sciences, 2019
    Co-Authors: Paul W. Simonin, Lars G. Rudstam, Patrick J. Sullivan, Donna L. Parrish, Bernard Pientka
    Abstract:

    We studied the consequences of a nonnative species introduction and changes in temperature on early mortality and recruitment of native rainbow smelt (Osmerus Mordax) and nonnative alewife (Alosa p...

  • hydroacoustic separation of rainbow smelt Osmerus Mordax age groups in lake champlain
    Fisheries Research, 2006
    Co-Authors: S Parker L Stetter, Lars G. Rudstam, J Stritzel L Thomson, Donna L. Parrish
    Abstract:

    Separate assessment of young-of-year (YOY) and yearling-and-older (YAO) fish is desirable from both ecological and management perspectives. Acoustic assessments provide information on fish population size structure in the target strength (TS) distribution, but interpretation of TS distributions must be done carefully, as single age groups can produce multiple TS modes. We assessed the ability of in situ TS distributions to identify Lake Champlain rainbow smelt (Osmerus Mordax) age groups in June, July, and September of 2001 using mobile and stationary surveys, knowledge of vertical distribution preferences, and predicted TS from trawl catches. YAO rainbow smelt (93–179 mm total length) had wide TS distributions between −60 and −35 dB in all 3 months with two modes at approximately −50 and −40 dB. Most stationary survey single-fish tracks attributed to YAO had targets in both TS modes and a wide TS range often over 15 dB. Between June and September, YOY rainbow smelt TS increased, but single-fish tracks were unimodal, and the TS range was smaller (6 dB). Overlap in TS attributed to YOY and YAO increased from no overlap in June (YOY TS −76 to −61 dB, 15–25 mm) to moderate overlap in July (−76 to −50 dB, 25–63 mm) to considerable overlap in September (−68 to −45 dB, 33–80 mm). In June and July, the TS distribution changed abruptly at the thermocline, indicating almost complete separation of the two groups. A more gradual TS transition was evident in September, indicating substantial overlap between YOY and YAO. Separate estimates can be obtained in September by decomposing TS overlap into components attributed to YOY and YAO rainbow smelt. However, this decomposition introduces additional uncertainty and an assessment in July or possibly August is preferable to obtain separate abundance estimates of YOY and YAO.

  • energetic consequences of diet shifts in lake erie rainbow smelt Osmerus Mordax
    Canadian Journal of Fisheries and Aquatic Sciences, 2005
    Co-Authors: S Parker L Stetter, Lars G. Rudstam, Larry D Witzel, Donald W Einhouse, E L Mills
    Abstract:

    The diet of eastern Lake Erie rainbow smelt (Osmerus Mordax) has changed since the 1960s, reflecting food resource shifts due to phosphorus reductions and the invasion of exotic species (dreissenid mussels and Bythotrephes longimanus). Since rainbow smelt growth was lower in the 1990s than in the 1960s, we considered diet changes as an explanation. A decrease in the proportion of zooplankton occurred in the summer (May–August) diet of two size classes (63–88 and 89–114 mm fork length) between 1961 and 1999. Within the zooplankton, the proportion of Bythotrephes increased. In spite of these changes, energy density (joules per gram) of the summer (June–August) diet has not changed since 1961. However, during the late-summer and fall, predation on Bythotrephes, and therefore the proportion of indigestible spines in the stomach, increases. Using bioenergetics models, we show that Lake Erie rainbow smelt could achieve 66%–155% greater growth between June and October if Bythotrephes spines were replaced with di...

  • cercopagis pengoi as a new prey item for alewife alosa pseudoharengus and rainbow smelt Osmerus Mordax in lake ontario
    Journal of Great Lakes Research, 2003
    Co-Authors: Tara M Bushnoe, Lars G. Rudstam, David M Warner, Edward L Mills
    Abstract:

    Diets of alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus Mordax) were examined before (1997) and after (1998 and 1999) the establishment of the predatory cladoceran Cercopagis pengoi in Lake Ontario. Cercopagis pengoi was absent in both fish stomachs and zooplankton samples in 1997, but by August 1998, its distribution was lake-wide and spines of this organism were present in stomachs of both fish species. Incidence of C. pengoi spines was highest in adult alewives. Spines occurred in 72, 100, and 90% of stomachs in August 1998, August 1999, and October 1999, respectively. Spines were found in 15 and 53% of YOY alewife stomachs in August 1998 and October 1999, respectively. Cercopagis pengoi spines were least common in rainbow smelt stomachs (12% in August 1998 and 6% in October 1999). Low frequency of occurrence in rainbow smelt likely resulted from limited spatial overlap with C. pengoi. No C. pengoi spines were found in alewives > 66 mm total length (TL) which suggests that consumption of C. pengoi by YOY alewife is limited by the long caudal spine. Low consumption of C. pengoi by YOY alewife may explain the remarkably rapid population increase of C. pengo i in Lake Ontario in 1998 in the presence of a strong alewife year class. These results indicate that C. pengoi is a competitor of YOY alewives for zooplankton during the summer but also a potential prey item for larger fish throughout the year and for YOY alewife in the fall.