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Gary K. Meffe - One of the best experts on this subject based on the ideXlab platform.
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SINGLE- AND MULTIPLE-LOCUS GENOTYPES AND LIFE-HISTORY RESPONSES OF Gambusia holbrooki REARED AT TWO TEMPERATURES.
Evolution; international journal of organic evolution, 1994Co-Authors: Margaret Mulvey, Gwen P. Keller, Gary K. MeffeAbstract:Eastern mosquitofish (Gambusia holbrooki) were reared from birth to 10 wk of age at 25°C and 32°C. Relationships of growth, time to maturity, and developmental stability to isozyme genotype were used to examine the hypothesis that more heterozygous individuals should exhibit superior performances, especially under thermally stressful (32°C) conditions. More heterozygous fish grew faster than homozygous individuals, especially at 32°C. Significant differences in time to maturity were detected among allozyme genotypes but not with heterozygosity. Multiple-locus heterozygosity was negatively related to fluctuating asymmetry. Thus, life-history traits were affected by both multiple-locus heterozygosity and single-locus genotype.
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Lipid Dynamics during Reproduction in Two Livebearing Fishes, Gambusia holbrooki and Poecilia latipinna
Canadian Journal of Fisheries and Aquatic Sciences, 1993Co-Authors: Gary K. Meffe, Franklin F. SnelsonAbstract:In animals, strategies of energy allocation among growth, maintenance and reproduction can be significantly altered by lipid storage. Poeciliid (livebearing) fishes store energy in late summer and fall for overwintering and first reproduction in spring, but details of energy use in reproduction are lacking. We conducted a laboratory experiment on the eastern mosquitofish (Gambusia holbrooki) and the sailfin molly (Poecilia latipinna) to document changes in lipid content in both the ovary and soma during development of a brood. In females of both species, ovarian lipid content was highest early in embryogeny and then declined; adult somatic lipids increased (were replenished) during embryonic development in mosquitofish, but declined in mollies. Larger clutches sequestered a larger share of body lipids in both species, possibly indicating energetic limits to reproduction. Finally, growth rate was positively correlated with somatic lipid content in both species, indicating among-individual differences in me...
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Plasticity of Life-History Characters in Eastern Mosquitofish (Gambusia holbrooki: Poeciliidae) in Response to Thermal Stress
Copeia, 1992Co-Authors: Gary K. MeffeAbstract:Eastern mosquitofish (Gambusia holbrooki) from a population exposed to abnormally high temperatures for 28 years were raised from birth in environmental chambers at 25 C (a normal temperature) or 32 C (a stressful temperature). Fish grew faster and larger at 25 C and were in better somatic condition than were fish grown at 32 C. There were no differences in ovum production at the two temperatures. At the higher temperature, fish matured at a younger age and a smaller size than did those at the normal temperature. This particular age-size at maturity relationship is not included as one of the predicted norms of reaction of a model by Stearns and Koella (1986) that deals with age and size at maturity under various growth rates. Gambusia holbrooki is a highly plastic species, which makes it adaptable to a variety of conditions, but also complicates interpretations of its interpopulation life-history differences; much of its life-history variation may be a consequence of different developmental environments rather than adaptive responses to demographic conditions.
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Life History Changes in Eastern Mosquitofish (Gambusia holbrooki) Induced by Thermal Elevation
Canadian Journal of Fisheries and Aquatic Sciences, 1991Co-Authors: Gary K. MeffeAbstract:Much light can be shed on life history evolution through study of responses of organisms to chronic exposure to a novel or perturbed environment. To determine the influence of 28 yr of temporally unpredictable thermal elevation on their life history patterns, I sampled eastern mosquitofish (Gambusia holbrooki) from a thermally elevated (outflow from a nuclear reactor) and an ambient (farm pond) habitat in South Carolina every month for 2 yr. Fish from the artificially heated environment reproduced all year, had higher reproductive investments (higher clutch sizes and reproductive biomass), and smaller offspring than did fish from the ambient environment, which ceased reproduction from October through March, typical for natural populations of the region. Likely environmental factors responsible for these differences include unpredictable food resources, higher mortality from thermal death, and higher predation by fishes and birds in the heated waters. The extent to which these life history alterations are ...
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Life History Changes in Eastern Mosquitofish (Gambusia holbrooki) Induced by Thermal Elevation
Canadian Journal of Fisheries and Aquatic Sciences, 1991Co-Authors: Gary K. MeffeAbstract:Much light can be shed on life history evolution through study of responses of organisms to chronic exposure to a novel or perturbed environment. To determine the influence of 28 yr of temporally unpredictable thermal elevation on their life history patterns, I sampled eastern mosquitofish (Gambusia holbrooki) from a thermally elevated (outflow from a nuclear reactor) and an ambient (farm pond) habitat in South Carolina every month for 2 yr. Fish from the artificially heated environment reproduced all year, had higher reproductive investments (higher clutch sizes and reproductive biomass), and smaller offspring than did fish from the ambient environment, which ceased reproduction from October through March, typical for natural populations of the region. Likely environmental factors responsible for these differences include unpredictable food resources, higher mortality from thermal death, and higher predation by fishes and birds in the heated waters. The extent to which these life history alterations are the result of adaptive genetic changes versus phenotypically plastic responses remains to be tested.
Margaret Mulvey - One of the best experts on this subject based on the ideXlab platform.
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SINGLE- AND MULTIPLE-LOCUS GENOTYPES AND LIFE-HISTORY RESPONSES OF Gambusia holbrooki REARED AT TWO TEMPERATURES.
Evolution; international journal of organic evolution, 1994Co-Authors: Margaret Mulvey, Gwen P. Keller, Gary K. MeffeAbstract:Eastern mosquitofish (Gambusia holbrooki) were reared from birth to 10 wk of age at 25°C and 32°C. Relationships of growth, time to maturity, and developmental stability to isozyme genotype were used to examine the hypothesis that more heterozygous individuals should exhibit superior performances, especially under thermally stressful (32°C) conditions. More heterozygous fish grew faster than homozygous individuals, especially at 32°C. Significant differences in time to maturity were detected among allozyme genotypes but not with heterozygosity. Multiple-locus heterozygosity was negatively related to fluctuating asymmetry. Thus, life-history traits were affected by both multiple-locus heterozygosity and single-locus genotype.
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Allozyme genotype in mosquitofish, Gambusia holbrooki, during mercury exposure : temporal stability, concentration effects and field verification
Environmental Toxicology and Chemistry, 1993Co-Authors: M. G. Heagler, Margaret Mulvey, Michael C. Newman, Philip M. DixonAbstract:Genotype frequencies at nine enzyme loci were examined in a population of mosquitofish, Gambusia holbrooki, during acute inorganic mercury exposure at three concentrations. Genotype at one locus, glucose phosphate isomerase-2 (Gpi-2), was correlated with time to death (TTD) at the low (0.83 mg/L) mercury concentration, but genotypes at none of the nine loci were related to TTD at the medium (1.07 mg/L) or the high (1.13 mg/L) mercury concentration. A survey of mosquitofish from a mercury-contaminated canal was undertaken to determine if the results of laboratory exposures could be used to predict accurately the genetic profile of mercury-contaminated field populations. Mosquitofish collected from the contaminated canal had a significantly lower frequency of the Gpi-238 allele than mosquitofish collected from the adjacent noncontaminated river. The Gpi-2 allozymes may be useful as an indicator of pollutant stress if used in conjunction with a thorough understanding of the structure and history of the population.
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Time effects on enzyme activity in the mosquitofish, Gambusia holbrooki
Environmental Toxicology and Chemistry, 1992Co-Authors: M. G. Heagler, Margaret MulveyAbstract:A study to examine the maximum interval between time of death and enzymatic sampling was conducted to determine the appropriate interval to procure reliable data from electrophoretic analysis of mosquitofish, Gambusia holbrooki. Dead fish were sampled at regular time intervals (0, 8, 12, 24 hours) and electrophoresed. All 26 of the enzyme systems assayed were reliably scorable 8 hours after death, with a large number remaining scorable up to 24 hours after death.
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Time to death of mosquitofish (Gambusia holbrooki) during acute inorganic mercury exposure: Population structure effects
Archives of environmental contamination and toxicology, 1992Co-Authors: Charles J. Lee, Michael C. Newman, Margaret MulveyAbstract:Times-to-death (TTD) of mother and offspring mosquitofish (Gambusia holbrooki) were examined during acute exposure to mercury concentrations of approximately 1.0 mg/L. Median TTD were more similar for fish sharing a common mother (defined herein as a sibship) and microhabitat during maturation than between sibships. Field populations may exhibit structure similar to that of these sibships. Correlations between broods (or other population subunits) and allozyme genotype could be responsible for transient, genotype effects noted during electrophoretic surveys attempting to measure population level response to toxicants.
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Glycolysis and krebs cycle metabolites in mosquitofish, Gambusia holbrooki, girard 1859, exposed to mercuric chloride : allozyme genotype effects
Environmental Toxicology and Chemistry, 1992Co-Authors: Michael C. Newman, Margaret Mulvey, Vincent J. Kramer, Gordon R. UltschAbstract:Concentrations of glycolysis and Krebs (citric acid) cycle metabolites were measured in the tail tissues of mosquitofish (Gambusia holbrooki, Girard 1859) in response to exposure to 0.86 mg/L Hg (as HgCl2) for 28 h. Substrate and product concentrations were compared between allozyme genotypes at two loci (glucosephosphate isomerase-2 and malate dehydrogenase-1) to determine whether allozyme genotypes in mosquitofish were differentially inhibited by mercury. Mercury treatment, regardless of allozyme genotype, caused decreased concentrations of glucose-6-phosphate (-27%) and lactate (-27%). Mercury treatment led to increased concentrations of malate (+33%) and oxaloacetate (+28%). Increased Krebs cycle activity could have been a response to greater energy needs associated with maintaining homeostasis under stressful conditions. There was no evidence of differential inhibition of allozymes at either locus. Fish of genotype Gpi-238/38 exhibited an overall increase in glycolytic activity in response to mercury treatment.
Michael Mahony - One of the best experts on this subject based on the ideXlab platform.
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stable isotope analyses reveal predation on amphibians by a globally invasive fish Gambusia holbrooki
Aquatic Conservation-marine and Freshwater Ecosystems, 2016Co-Authors: Jonathan Remon, Deborah S. Bower, Troy F. Gaston, John Clulow, Michael MahonyAbstract:Biodiversity loss caused by invasive species is particularly problematic in freshwater ecosystems, which are among the world's most threatened habitats. Invasive fish such as the eastern mosquitofish, Gambusia holbrooki, have been implicated in the decline of amphibians, which suffer high extinction rates globally. Although G. holbrooki is one of the most studied freshwater fish, its diet shows wide geographic variation and its impact on amphibian populations remains unclear. Stable isotopes 13C and 15N were used in 10 urban ponds in Sydney, Australia to compare the diet of G. holbrooki in January, April and May 2013 using a stable isotope mixing model. Gambusia holbrooki was carnivorous and fed on invertebrates (24–39%), tadpoles (25–32%) and conspecifics (20–45%). In contrast to previous studies, primary producers were a negligible part of Gambusia holbrooki diet (<10%). Its diet in late autumn comprised a high proportion of conspecifics (up to 45%) owing to the depletion of other food sources before winter (metamorphosis of larvae). This study provides evidence of high rates of predation on native tadpoles and invertebrates by a highly invasive fish. This knowledge should be incorporated into amphibian releases through head-starting tadpoles or using soft releases where tadpoles are placed in predator-free enclosures until larvae are large enough to avoid predation. Considering the dire conservation status of amphibians globally and the growing interest for invertebrates, it is suggested that stable isotopes are valuable to identify threats from predation in order to target conservation practice toward suitable priorities.
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Stable isotope analyses reveal predation on amphibians by a globally invasive fish (Gambusia holbrooki)
Aquatic Conservation: Marine and Freshwater Ecosystems, 2016Co-Authors: Jonathan Remon, Deborah S. Bower, Troy F. Gaston, John Clulow, Michael MahonyAbstract:Biodiversity loss caused by invasive species is particularly problematic in freshwater ecosystems, which are among the world's most threatened habitats. Invasive fish such as the eastern mosquitofish, Gambusia holbrooki, have been implicated in the decline of amphibians, which suffer high extinction rates globally. Although G. holbrooki is one of the most studied freshwater fish, its diet shows wide geographic variation and its impact on amphibian populations remains unclear. Stable isotopes 13C and 15N were used in 10 urban ponds in Sydney, Australia to compare the diet of G. holbrooki in January, April and May 2013 using a stable isotope mixing model. Gambusia holbrooki was carnivorous and fed on invertebrates (24–39%), tadpoles (25–32%) and conspecifics (20–45%). In contrast to previous studies, primary producers were a negligible part of Gambusia holbrooki diet (
Jonathan Remon - One of the best experts on this subject based on the ideXlab platform.
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stable isotope analyses reveal predation on amphibians by a globally invasive fish Gambusia holbrooki
Aquatic Conservation-marine and Freshwater Ecosystems, 2016Co-Authors: Jonathan Remon, Deborah S. Bower, Troy F. Gaston, John Clulow, Michael MahonyAbstract:Biodiversity loss caused by invasive species is particularly problematic in freshwater ecosystems, which are among the world's most threatened habitats. Invasive fish such as the eastern mosquitofish, Gambusia holbrooki, have been implicated in the decline of amphibians, which suffer high extinction rates globally. Although G. holbrooki is one of the most studied freshwater fish, its diet shows wide geographic variation and its impact on amphibian populations remains unclear. Stable isotopes 13C and 15N were used in 10 urban ponds in Sydney, Australia to compare the diet of G. holbrooki in January, April and May 2013 using a stable isotope mixing model. Gambusia holbrooki was carnivorous and fed on invertebrates (24–39%), tadpoles (25–32%) and conspecifics (20–45%). In contrast to previous studies, primary producers were a negligible part of Gambusia holbrooki diet (<10%). Its diet in late autumn comprised a high proportion of conspecifics (up to 45%) owing to the depletion of other food sources before winter (metamorphosis of larvae). This study provides evidence of high rates of predation on native tadpoles and invertebrates by a highly invasive fish. This knowledge should be incorporated into amphibian releases through head-starting tadpoles or using soft releases where tadpoles are placed in predator-free enclosures until larvae are large enough to avoid predation. Considering the dire conservation status of amphibians globally and the growing interest for invertebrates, it is suggested that stable isotopes are valuable to identify threats from predation in order to target conservation practice toward suitable priorities.
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Stable isotope analyses reveal predation on amphibians by a globally invasive fish (Gambusia holbrooki)
Aquatic Conservation: Marine and Freshwater Ecosystems, 2016Co-Authors: Jonathan Remon, Deborah S. Bower, Troy F. Gaston, John Clulow, Michael MahonyAbstract:Biodiversity loss caused by invasive species is particularly problematic in freshwater ecosystems, which are among the world's most threatened habitats. Invasive fish such as the eastern mosquitofish, Gambusia holbrooki, have been implicated in the decline of amphibians, which suffer high extinction rates globally. Although G. holbrooki is one of the most studied freshwater fish, its diet shows wide geographic variation and its impact on amphibian populations remains unclear. Stable isotopes 13C and 15N were used in 10 urban ponds in Sydney, Australia to compare the diet of G. holbrooki in January, April and May 2013 using a stable isotope mixing model. Gambusia holbrooki was carnivorous and fed on invertebrates (24–39%), tadpoles (25–32%) and conspecifics (20–45%). In contrast to previous studies, primary producers were a negligible part of Gambusia holbrooki diet (
Louis J. Guillette - One of the best experts on this subject based on the ideXlab platform.
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seasonal reproduction of male Gambusia holbrooki eastern mosquitofish from two florida lakes
Fish Physiology and Biochemistry, 2013Co-Authors: Thea M. Edwards, Gunnar Toft, Hillary D Miller, Louis J. GuilletteAbstract:Sixteen monthly collections of adult male Gambusia holbrooki (eastern mosquitofish) were obtained from two lakes in central Florida, USA. Lake Woodruff and Lake Apopka are 36 miles apart, but differ in several environmental parameters. Compared with Lake Woodruff, Lake Apopka is warmer, more shallow in sampling areas (particularly during drought conditions; approximately 15–90 cm in Lake Apopka versus 60–120 cm in Lake Woodruff), more turbid, and more heavily contaminated with nutrients and industrial and agricultural chemicals. Here, we present detailed information on seasonal reproduction patterns in mosquitofish in their native range and compare patterns between fish from the two lakes. Male mosquitofish were reproductively active from spring through fall. Spermatogenesis, which is regulated in part by 11-ketotestosterone, ceased in October, and fish stored spermatozoa through the winter for immediate fertilization of offspring in the spring. Compared with Lake Woodruff, fish from Lake Apopka tended to be larger and have longer gonopodia and greater gonado- and hepato-somatic indices (GSI and HSI). High GSI in Apopka fish correlated with greater spermatid production, but fewer mature spermatozoa and either the same or lower sperm counts and sperm viability. Taken together, these observations suggest that differentiation of spermatids to spermatozoa is disrupted in Apopka fish, leading to reductions in fertility in some months. Delivery of sperm to females could also be affected in Apopka fish, which exhibit lower prevalence of efferent duct tissue in the testes during the summer.
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Seasonal reproductive patterns of female Gambusia holbrooki from two Florida lakes.
The Science of the total environment, 2010Co-Authors: Thea M. Edwards, Gunnar Toft, Louis J. GuilletteAbstract:Abstract Lake Apopka in central Florida (USA) is significantly contaminated with a variety of chemicals including anthropogenic nutrients, organochlorine pesticides like dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE), and multiple congeners of polychlorinated biphenyls (PCBs). Our laboratory has previously documented a number of reproductive abnormalities in alligators from Lake Apopka, compared with alligators captured from Lake Woodruff, a nearby reference lake. We conducted the present study to investigate if another native vertebrate, Gambusia holbrooki (eastern mosquitofish), is similarly affected. Adult female mosquitofish were collected from Lake Apopka and Lake Woodruff monthly for 16 months to document seasonal and lake-associated variation in reproductive patterns. In contrast to fish from Lake Woodruff (reference), females from Lake Apopka exhibited earlier and more synchronized spring ovarian recrudescence, increased body size, increased fecundity, increased adjusted hepatic weight, and more extreme fluctuations in muscle estradiol concentrations in most months. Endocrine disruption, consistent with other studies and Lake Apopka's pollution profile, is one explanation for these findings. Other environmental and physiological factors are also addressed. However, the higher fecundity among Apopka females suggests that, unlike Apopka alligators, Apopka mosquitofish are not impacted at the population level.
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reproductive characteristics of male mosquitofish Gambusia holbrooki from nitrate contaminated springs in florida
Aquatic Toxicology, 2007Co-Authors: Thea M. Edwards, Louis J. GuilletteAbstract:Abstract Over the past five decades, anthropogenic nitrate contamination has increased significantly in many ground and surface water systems, creating the need to understand how nitrate impacts the physiology of aquatic animals. We collected adult male mosquitofish (Gambusia holbrooki) from eight springs in Florida with varying nitrate concentrations (0.2–5.1 mg/L NO3-N). Fish were evaluated for spring-related differences in body, liver, and gonad size, gonopodium length, muscle testosterone and 11-ketotestosterone (11-KT) concentrations, and sperm counts and viability. Increased nitrate concentration (up to 5 mg/L NO3-N) was significantly correlated with decreased total sperm counts per spermatozeugmatum, increased adjusted gonopodium length, and increased adjusted testicular weight. Furthermore, we observed that relatively small differences in spring pH (7.0–7.4) were positively associated with muscle 11-KT concentrations. Finally, minor changes in spring water temperature (21.4–22.9 °C) was negatively correlated with adjusted testicular and hepatic weights, and positively correlated with total and live sperm counts. We conclude that male mosquitofish reproduction is not the same among the eight springs tested, and that elevated aquatic nitrate concentrations may explain some of the observed variation.
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water quality influences reproduction in female mosquitofish Gambusia holbrooki from eight florida springs
Environmental Health Perspectives, 2006Co-Authors: Thea M. Edwards, Hillary D Miller, Louis J. GuilletteAbstract:Contamination of freshwater ecosystems with nitrate is a growing global concern. Although nitrate pollution is recognized as a cause of aquatic eutrophication, few studies have examined the possible physiological impacts of nitrate exposure. In this study, we surveyed several reproductive variables of viviparous female Gambusia holbrooki (Poeciliidae) captured from eight springs in Florida. The eight springs represent a gradient of nitrate contamination (1-5 mg/L nitrate-nitrogen). We had two objectives in this study: to describe reproductive biology of female mosquitofish in the springs and to understand reproductive variation in the context of water quality, particularly the nitrate concentration. Our data show a significant negative association between nitrate and both dry weight of developing embryos and rate of reproductive activity among mature females. In addition, variation in Gambusia condition index and embryo number and dry weight was related to temperature variation, and hepatic weight was negatively related to dissolved oxygen concentration. Finally, we observed that many of the measured reproductive variables were interrelated and changeable, depending on gestational stage. Specifically, we provide evidence that maternal support of the embryo occurs at least during the first two thirds of gestation and that female fecundity is affected by an apparent tradeoff between embryo size and embryo number.
