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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Relations between Environmentally Disturbing Establishments and three Invertebrate Indicator Species in the Baltic Sea

Joelsson, Anna-Emilia January 2013 (has links)
In order to improve the knowledge about polluted areas in Sweden, Naturvårdsverket has compiled a list of all establishments and other anthropological activities, so called MIFOobjects, which emit harmful chemicals. Those activities which are placed on land might, depending on factors such as closeness to the sea, water solubility, degradability and toxicity of the chemicals have an impact on the biota in the Baltic Sea. In this study, spatial and statistical methods were used to explore potential relations between the abundance of three indicator organisms (Macoma balthica, Marenzelleria and Monoporeia affinis), closeness and a second variable built risk class of MIFO-objects and local environmental factors (e.g., sea depth, salinity) at the coast of Blekinge. The impact of MIFO-objects on the abundance of the indicator organisms was analyzed with both graphical and numerical multivariate analysis methods such as spearman analysis, principal component analysis and canonical component analysis. Four types of variables were created to enable the analysis. The first two variables were based one distance from emission locations to the study sites. The other pair of variables comprised on variable built on the cumulative risk assessment of the MIFO-objects given by Naturvårdsverket and another that was based on a classification of the emitted pollutants according to their chemical toxicity. The analysis showed that the abundance of Marenzelleria was positively correlated with MIFO-objects both in terms of risk assessment and chemical toxicity. This was probably a result of the fact that Marenzelleria is less sensitive to pollutants and therefore more competitive than other species in its habitat. Since the abundance of Macoma balthica covaried a lot with environmental factors such as salinity it was difficult to distinguish the impact of MIFO-object on the mussel. The statistical base of the abundance of Monoporeia affinis was too small to make any conclusions about what is describing the abundance.
12

Disc electrophoresis studies of the soluble proteins of the Peniophora affinis and Peniophora cinerea groups

Harris, Robert J. Liberta, Anthony E. January 1971 (has links)
Thesis (Ph. D.)--Illinois State University, 1971. / Title from title page screen, viewed Sept. 21, 2004. Dissertation Committee: Anthony E. Liberta (chair), E. Willis, D. Birkenholz, W. Daniel, M. Nadakavukaren. Includes bibliographical references (leaves 41-44) and abstract. Also available in print.
13

The relation of thyroid function to upper lethal temperature in Gambusia affinis

Theobald, P. V. Kurian. January 1959 (has links)
Thesis--Catholic University of America. / Bibliography: p. 25-29.
14

Helmintofauna em Cerdocyon thous Linnaeus, 1766 (Carnivora, Canidae) na região de Juiz de Fora, Minas Gerais

Duarte, Fabrício Horta 13 February 2007 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-04T19:36:43Z No. of bitstreams: 1 fabriciohortaduarte.pdf: 1008367 bytes, checksum: d101b8e040e543ba247884ffb2be3f2b (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-06T10:44:27Z (GMT) No. of bitstreams: 1 fabriciohortaduarte.pdf: 1008367 bytes, checksum: d101b8e040e543ba247884ffb2be3f2b (MD5) / Made available in DSpace on 2017-04-06T10:44:27Z (GMT). No. of bitstreams: 1 fabriciohortaduarte.pdf: 1008367 bytes, checksum: d101b8e040e543ba247884ffb2be3f2b (MD5) Previous issue date: 2007-02-13 / O cachorro do mato (Cerdocyon thous) é um canídeo típico da fauna Sul americana, apresenta hábitos noturnos e é amplamente distribuído pelo território nacional. O presente trabalho objetivou contribuir, principalmente, com o avanço do conhecimento sobre taxonomia das espécies de helmintos que ocorrem em C. thous. Foram necropsiados seis espécimes do dito hospedeiro, dentre os anos de 2001 e 2004, morto em atropelamentos em estradas da micro região de Juiz de Fora, Minas Gerais. Os helmintos foram coletados e acondicionados em via úmida e via seca. Para identificação específica, foram montados em lâminas permanentes e provisórias. Foram encontrados, 468 helmintos identificados como: Angiostrongylus vasorum (Baillet, 1866) Kamensky, 1905 (Nematoda, Angiostrogylidae), a uma prevalência de 50% (P=50%), abundancia média de 4±4,47 (AM=4±4,47), intensidade média de 8±3,00 (IM=8±3,00) e padrão distribuição espacial agregado (ID=5,70 e K=0,36), sendo esta espécie um espécie secundária na comunidade, no coração e nos pulmões de três hospedeiros analisados, Platynosomum illiciens (Braun, 1901) Kossack, 1910 (Digenea, Dicrocoeliidae) (P=16,7%; AM= 6±14,69; IM= 36) no fígado e ductos biliares de um hospedeiro, sendo esta espécie satélite na comunidade, Ancylostomma bucklelyi Le Roux and Biocca, 1957 (Nematoda, Ancylostomatidae) (P=33,4%; AM= 2±3,09; IM= 6) padrão agregado de distribuição (ID=0,57; K=6,32), sendo esta espécie secundária na comunidade, encontrada no intestino delgado e estômago de dois hospedeiros, Pterygodermatites affinis (Jägerskiöld 1904) Quentin, 1969 (Nematoda, Rictulariidae) (P=66,7%; AM= 5±7,64; IM= 7,5±8,5) apresenta padrão de distribuição espacial agregado (ID=0,56 e K=0,44) e é uma espécie central na comunidade, sendo encontrada em intestino e estômago de quatro hospedeiros, Athesmia heterolecithodes (Braun, 1899) Looss, 1899 (Digenea, Dicrocoeliidae) (P=33,4%; AM= 59,83±140,76; IM= 179,5±236,88) sendo uma espécie secundária na comunidade, relatada parasitando o fígado de dois hospedeiros e uma espécie de capilarídeo não identificada em um hospedeiro. O presente trabalho é o primeiro registro de A. heterolecitodes, P. affinis, P. illiciens para C. thous. / Cerdocyon thous is a canid of neotropical fauna, with nocturnal habits and extensive distribution in the savannas and forests of South America. The objective of this work is contribute for the knowledge about helminthes species in C. thous. Were examined six specimens of C. thous dead by running over in the periphery of the Juiz de Fora, Minas Gerais, Brazil. The helminths was collected and stored in 70 % alcohol and dry preparations. For specific identification, they were prepared in permanent and no permanent slides. Angiostrongylus vasorum (Baillet, 1866) Kamensky, 1905 (Nematoda, Angiostrogylidae) occurred in heart and lungs in tree hosts, with a prevalence of 50% (P=50%), mean abundance of 4±4,47 (MA=4±4,47), mean intensity of 8±3,00 (MI=8±3,00) and spatial distribution agregated (ID=5,70 e K=0,36). This species has been characterized as secondary in the community of parasites. Platynosomum illiciens (Braun, 1901) Kossack, 1910 (Digenea, Dicrocoeliidae) (P=16,7%; MA= 6±14,69; MI= 36) occurred in liver of one host and was categorized as satellite among parasites populations. Ancylostomma bucklelyi Le Roux and Biocca, 1957 (Nematoda, Ancylostomatidae) (P=33,4%; MA= 2±3,09; MI= 6) occurred in small intestine and stomach in two hosts, with spatial distribution agregated (ID=0,57; K=6,32), and was categorized as secondary. Pterygodermatites affinis (Jägerskiöld 1904) Quentin, 1969 (Nematoda, Rictulariidae) (P=66,7%; MA= 5±7,64; MI= 7,5±8,5), was registered in intestine and stomach in four hosts and showed spatial distribution agregated (ID=0,56 e K=0,44). P affinis was the only central species in the parasites community. Athesmia heterolecithodes (Braun, 1899) Looss, 1899 (Digenea, Dicrocoeliidae) (P=33,4%; MA= 59,83±140,76; MI= 179,5±236,88), a secondary parasites species, was registered in liver of the two host. A not identify species of nematodes Capilariidae was recorded in one host. This study are the first record of A. heterolecithodes, P. affinis, P. illiciens in C. thous.
15

Rôle du mésozooplancton dans un estuaire restauré : l'Escaut / Role of zooplankton in a restoring estuary : the Scheldt

Chambord, Sophie 16 June 2016 (has links)
L'estuaire de l'Escaut est un estuaire en voie de restauration. L'étude s'intéresse à l'écologie de la communauté zooplanctonique dans le tronçon d'eau douce de l'Escaut, ou, suite à l'amélioration de la qualité de l'eau le copépode calanoide Eurytemora affinis est devenu dominant depuis 2007 et les copépodes cyclopoïdes ont diminués en abondance. Nous avons cherché à trouver quels facteurs environnementaux expliquent ce changement de la composition de la communauté zooplanctonique. Les résultats d'analyses RDA et GLM entre les abondances des taxons zooplanctoniques et les facteurs environnementaux montrent un lien étroit entre l'augmentation de l'abondance d'E. affinis et l'augmentation des concentrations en oxygène ainsi que la diminution des concentrations en N-NH4. En fait, le tronçon amont de l'estuaire est devenu 'permissive' pour le développement d'E. affinis à partir ou la concentration en O2 a dépassé le seuil de 4 mg L-1 et la concentration en N- NH4 est restée en dessous de 2 mg L-1. La cause du déclin en abondance des cyclopoids reste à trouver. Dans l'Escaut, le phytoplancton est fortement dominé par les diatomées, mais la concentration en Si dissoute s'avère parfois limitant. La question se pose sur quelles composantes de la communauté phytoplanctonique le zooplancton dominant se nourrit. La sélectivité de broutage d'E. affinis a été quantifiée à l'aide d'expériences d'incubation et des quantification de contenu pigmentaire à l'aide d'HPLC. E. affinis sélectionne des diatomées au sein de la communauté phytoplanctonique et en moindre mesure des cryptomonades. L'impact de la population d'E. affinis sur le stock de phytoplancton - et sur les diatomées dominantes- est < 4.5 % jour-1, ce qui implique que dans le tronçon d'eau douce de l'Escaut le zooplancton n'est pas limité par la nourriture et ne présente pas de limitation pour le développement les niveaux trophiques supérieurs. Certains taxons phytoplanctoniques (chlorophycées, par exemple) sont apparemment stimulés en croissance par la présence d'E. affinis dans les bouteilles expérimentales et l'impact précis d'E. affinis sur le phytoplancton non-diatomées est moins clair. L'activité de broutage du microzooplancton a également été testée avec des expériences d'incubation. Son impact sur la communauté phytoplanctonique est variable en intensité et en sélectivité, nécessitant plus d'expérimentation. / The Scheldt is an estuary on way of recovery. The study concerns the ecology of the zooplankton community in the freshwater reach of the estuary. In parallel to water quality improvement, the copepod Eurytemora affinis has become dominant since 2007 and abundance of cyclopoid copepods has decreased. We tried to find out which environmental factors had caused these changes in the zooplankton community composition. The results of RDA and GLM analysis between the abundance of zooplankton taxa and the environmental factors showed a strong link between E. affinis abundance and the increasing O2 concentration, but also the decreasing NH4-N concentration. The upstream Scheldt became permissive for E. affinis development as soon as oxygen concentration was above the threshold level of 4 mg L-1 and the NH4-N concentration remained below 2 mg L-1. The cause of the decrease in cyclopoid abundance remains unclear. The phytoplankton community of freshwater Scheldt is strongly dominated by diatoms, but the dissolved silica concentration could become limiting for their development. The question arises on which phytoplankton taxa the dominant zooplankton feeds. Grazing selectivity of E. affinis adults and CV was measured by incubation experiments using natural Scheldt water and by gut pigment content quantification. Phytoplankton taxa concentration was quantified by HPLC. E. affinis selects diatoms and sometimes cryptophytes. The impact of the E. affinis population on the phytoplankton standing stock is < 4.5% d-1, which means that the zooplankton community is not food limited and hence does not present a limitation to the development of higher trophic levels. The grazing activity of the microzooplankton community has also been measured by incubation experiments. Its impact on the freshwater Scheldt phytoplankton community is variable in intensity and in selectivity, and clearly needs further investigation.
16

Approche intégrée des conditions physico-chimiques affectant les cortèges biologiques de la partie fluviale de l'estuaire de la Gironde / Integrated approach to the physico-chemical conditions affecting the biological components in the fluvial section of the Gironde estuary

Dindinaud, Francois 04 February 2015 (has links)
Les estuaires, situés à l’interface entre les domaines continental et marin, constituent des zones essentielles dans les échanges de matières. Ils jouent dès lors un rôle capital pour les cycles biogéochimiques et biologiques et subissent, par ailleurs, des pressions climatiques et anthropiques croissantes depuis plusieurs décennies. Le présent travail a été focalisé sur les peuplements benthiques et pélagiques présents dans la partie fluviale (Garonne et Dordogne) de l’estuaire de la Gironde, zone àtrès faible salinité où ces peuplements n’avaient encore jamais été étudiés. Alors que la méiofaune, composée principalement de Nématodes, s’est avérée relativement abondante dans les domaines intertidal et subtidal, le macrobenthos est apparu composé essentiellement d’Oligochètes en intertidal et complètement absent en subtidal. La grande plasticité du copépode dominant Eurytemora affinis a été confirmée, celui-ci occupant une niche écologique différente dans la partie fluviale de l’estuaire par rapport à la zone haline. L’importance de la température plutôt que la qualité du pool nutritif sur la productivité d’E. affinis a été démontrée, mettant en évidence une fois de plus la grande adaptabilité de cette espèce dans un habitat très fluctuant. L’étude de l’habitat benthique et pélagique, notamment en terme de qualité du pool nutritif disponible pour les organismes, a démontré que la contribution de la matière organique réfractaire d’origine terrestre est dominante. La contribution du micro phytobenthos à la composition de la matière organique sédimentaire et pélagique a aussi été mise en évidence. Enfin,l’étude des communautés planctoniques dans la partie fluviale de l’estuaire de la Gironde a montré que l’espèce E. affinis y occupe une position clef. / Being at the interface between continental and marine systems, estuaries are essential areas for matter exchanges. Therefore, they play a crucial role in biological and biogeochemical cycles. In addition to natural fluctuations, these systems have also undergone increasing climate and anthropogenic pressures for several decades. The present work focused on the benthic and pelagic assemblages in the fluvial section (Garonne and Dordogne rivers) of the Gironde estuary, a low salinity area where these communities had never been studied. Meiofauna, mainly composed ofnematodes, was found in relatively high abundance in both intertidal and subtidal zones.Macrozoobenthos was essentially composed of oligochaetes in the intertidal, while it was totally absent in the subtidal areas. The high plasticity of the dominant copepod Eurytemora affinis was confirmed, with a different ecological niche in the freshwater section of the estuary compared to the haline area downstream. The importance of temperature rather than the quality of the nutrient pool on the productivity of E. affinis was demonstrated, thereby confirming the great adaptability of thisspecies to a highly fluctuating habitat. Study of benthic and pelagic habitat, especially in terms of quality of the nutrient pool available to the organisms, showed that the contribution of refractoryorganic matter with a terrestrial origin is dominant. A significant contribution of microphytobenthos to the composition of sedimentary and pelagic organic matter was also highlighted. Finally, the study of planktonic communities in the fluvial part of the Gironde estuary showed that the species E. affinis occupies a key position in this part of the estuary.
17

Influência de fatores do ambiente na germinação de sementes de grama-tapete (Axonopus affinis Chase) / Environmental factors influence in carpet grass (Axonoupus affinis CHASE) seed germination

Pereira, Suzana Targanski Sajovic [UNESP] 28 July 2016 (has links)
Submitted by SUZANA TARGANSKI SAJOVIC PEREIRA null (suzana_tsp@hotmail.com) on 2016-08-24T18:34:25Z No. of bitstreams: 1 Dissertação_Suzana_Targanski_Sajovic_Pereira.pdf: 2840184 bytes, checksum: e7bd2eed88ab9bd548d7561bb3b326d6 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-08-26T13:27:22Z (GMT) No. of bitstreams: 1 pereira_sts_me_jabo.pdf: 2840184 bytes, checksum: e7bd2eed88ab9bd548d7561bb3b326d6 (MD5) / Made available in DSpace on 2016-08-26T13:27:22Z (GMT). No. of bitstreams: 1 pereira_sts_me_jabo.pdf: 2840184 bytes, checksum: e7bd2eed88ab9bd548d7561bb3b326d6 (MD5) Previous issue date: 2016-07-28 / O objetivo deste trabalho foi verificar a influência da temperatura, da luz, do substrato, das formas de semeadura, do estresse salino e hídrico na germinação da gramínea Axonopus affinis. Foram quatro experimentos, todos conduzidos em câmara de germinação, onde as condições de temperatura, umidade e fotoperíodo foram controladas; o delineamento experimental utilizado foi inteiramente casualizado e utilizou-se 100 sementes por parcela. Para o estudo da temperatura e da luz (experimento 1), os tratamentos foram arranjados em esquema fatorial 6 x 2, composto de seis condições de temperatura (constante de 20, 25, 30 e 35 ºC e alternadas de 20-30 ºC e 20-35 ºC) e duas condições de luminosidade (―claro‖: 8 horas de luz e 16 horas de escuro e ―escuro‖: 24 h na ausência de luz) e quatro repetições. Para o estudo de substrato e forma de semeadura (experimento 2) foram quatro tratamentos (sobre papel, entre papel, sobre areia e entre areia) e cinco repetições. Para o estudo do estresse salino (experimento 3) foram cinco tratamentos (concentrações de NaCl: 0, 25, 50, 75 e 100 mM) e quatro repetições. Para o estudo do estresse hídrico e formas de semeadura (experimento 4), os tratamentos foram distribuídos em esquema fatorial 3 x 2 onde foram testados três níveis de capacidade de retenção de água (50, 75 e 100%) e duas formas de semeadura (sobre areia e entre areia) e quatro repetições. Avaliou-se porcentagem de germinação e Índice de Velocidade de Germinação. Concluiu-se que a germinação de sementes foi mais efetiva em temperaturas alternadas de 20-30 ºC e 20-35 ºC sob condição de luz e nos substratos sobre papel, entre papel e sobre areia; a concentração de NaCl não afetou a porcentagem de germinação, porém, o aumento da concentração diminuiu gradativamente a velocidade de germinação; maior porcentagem e velocidade de germinação ocorreu quando as sementes foram colocadas sobre areia, mantida com 100% da capacidade de retenção de água. / This work aim was verify the temperature, light, substrate, ways of sowing, and salt and hydric stress influence into the Axonopus affinis germination. All the four trials were carried out in a germination chamber under temperature, humidity, and photoperiod controlled conditions. The experimental design used was the completely randomized one, with 100 seeds in each plot. To study the temperature and light (experiment 1), the trials were arranged in a factorial scheme 6x2, with six temperature conditions (constant temperatures of 20, 25, 30 and 35 °C and alternate temperatures of 20-30 °C and 20-25 °C) and two lightning conditions (light: 8 hours of light and 16 hours of dark and "dark": 24 h in the dark) and four replications. To the substrate and sowing trial (experiment 2) we used four treatments (on paper, between paper, on sand, and between sand) with five replications. To the salt stress trial (experiment 3) we used five treatments (NaCl concentrations: 0, 25, 50, 75, and 100 mM) with four replications. To the hydric stress trial the treatments were arranged in a 3x2 factorial scheme (experiment 4) where we tested three levels of water retention capacity (50, 75, and 100%) and two ways of sowing (on sand and between sand) and four replications. We evaluated the germination percentage and Germination Time Index. We could conclude that the seed germination was more effective when the temperature was alternated of 20-30 °C and 20-35 °C, under light condition, and on a paper substrate, between papers and on the sand. The NaCl concentration did not affect the germination percentage. However, the higher was the NaCl concentration, the slower was the germination. A faster and higher germination occurred when seeds were on the sand kept at 100% of water retention capacity.
18

Proteína bruta e energia digestível em dietas para alevinos de curimbatá / Crude protein and digestible energy in the diets for curimbatá fingerlings

Bomfim, Marcos Antonio Delmondes 18 February 2003 (has links)
Submitted by Nathália Faria da Silva (nathaliafsilva.ufv@gmail.com) on 2017-07-11T16:14:25Z No. of bitstreams: 1 texto completo.pdf: 722614 bytes, checksum: 6ee5d0c0f6f0c93b80cb667755094f4c (MD5) / Made available in DSpace on 2017-07-11T16:14:25Z (GMT). No. of bitstreams: 1 texto completo.pdf: 722614 bytes, checksum: 6ee5d0c0f6f0c93b80cb667755094f4c (MD5) Previous issue date: 2003-02-18 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Objetivando-se determinar as exigências de proteína bruta (PB) em função do nível de energia digestível (ED) da dieta para alevinos de curimbatá (Prochilodus affins), foram utilizados 256 peixes com peso inicial de 2,72 ± 0,11 g, mantidos em 32 aquários de 100 litros dotados de abastecimento de água, temperatura controlada e aeração individuais. O experimento foi realizado seguindo-se um esquema fatorial 4 x 2 (quatro níveis de PB: 18,0; 22,0; 26,0; e 30,0%, combinados com dois níveis de ED: 2.700 e 3.000 kcal/kg) em um delineamento inteiramente ao acaso com quatro repetições e oito peixes por unidade experimental. Os peixes foram alimentados ad libitum em duas refeições, diárias durante 78 dias. Avaliaram-se o ganho de peso, o consumo de racão aparente, a conversão alimentar aparente, a taxa de crescimento específico, a taxa de eficiência protéica, a eficiência de retenção de nitrogênio, o índice hepatossomático, a umidade, a proteína e a gordura corporais e a porcentagem de nitrogênio e gordura no ganho de peso. Verificou-se que apenas o índice hepatossomático não diferiu entre as variáveis. Para os demais parâmetros não houve interações entre os níveis de PB e ED, à exceção da porcentagem de gordura no ganho de peso. Com o nível de 3.000 kcal de ED/kg, obtiveram-se peixes com maiores níveis de matéria seca, gordura corporal e porcentagem de gordura no ganho de peso. xConcluiu-se que a exigência de PB e ED para alevinos de curimbatá é de 26,05% e 2.700 kcal/kg, respectivamente, que corresponde a uma relação ED:PB de 10,36 kcal de ED/g de PB, por proporcionar as melhores respostas em ganho de peso e composição de carcaça. / Two hundred and fifty six curimbatá (Prochilodus affins) fingerlings with average initial weight of 2.72 ± 0.11 g, placed in 32 aquariums (100 L) with water renewal, controlled temperature and individual aeration, were used to determine the crude protein (CP) requirements, according to the digestible energy level (DE) in the diets. The experiment was carried out according to a 4 x 2 factorial scheme (four CP levels: 18.0, 22.0, 26.0 and 30.0% combined with two DE levels: 2,700 and 3,000 kcal/kg), in a completely randomized design, with four replicates and eight fishes per experimental unit. The fishes were ad libitum fed twice a day, during 78 days. Weight gain, apparent feed consumption, apparent feed:gain ratio, specific growth rate, protein efficiency rate, nitrogen retention efficiency, hepatic-somatic index, humidity, body fat and protein, nitrogen and fat percentage in the weight gain were evaluated. It was observed that only the hepatic-somatic index did not differ among the variables. No interaction was observed between the CP and DE levels, for any of the studied variables, except for the fat percentage in the weight gain. Fishes fed diets with 3,000 kcal de DE/kg showed higher levels of dry matter, body fat and fat percentage in weight gain. It was concluded that the CP and DE requirement for curimbatá fingerlings is xii26.05% and 2,700 kcal/kg, respectively, that corresponds to a DE:CP ratio of 10.36 kcal DE/g CP, due to the best results of weight gain and carcass composition.
19

Enemy Exacerbation: Effects of Predator Stress on Sulfate Lethality in Freshwater Amphipods (Gammarus minus)

Chapman, Trevor 01 August 2017 (has links) (PDF)
Predator cues can influence how aquatic organisms respond to anthropogenic contaminants. This study examined the effects of predator cues on behavior, metabolic rate, and sulfate (as Na2SO4) toxicity in amphipods (Gammarus minus). Predator cues included alarm cue (macerated conspecifics) and kairomone from mosquitofish (Gambusia affinis). Amphipods decreased activity and increased time in refuge when exposed to alarm cue, and increased time in refuge when exposed to kairomone. While median lethal concentrations (96-h LC50) were not influenced by predator cues, analysis of dose response curves indicated that kairomone exposure increased amphipod sensitivity to mid-range concentrations of sulfate (500-1,000 mg/L). Amphipods increased oxygen consumption in response to kairomone but not alarm cue. The influence of predator cues on contaminant lethality can be dependent on the type of cue, and physiological endpoints such as metabolic rate may help explain the basis of observed interactions.
20

An Invasive Species Reduces Aquatic Insect Flux to Terrestrial Food Webs

Merkley, Steven S. 11 July 2011 (has links) (PDF)
Although it is well documented how introduced species can negatively affect native species, we only poorly understand how they may alter ecosystem functions. We investigated how an invasive fish affected the flux of aquatic insects to terrestrial food webs using mesocosms in a desert spring ecosystem. We compared aquatic insect emergence between alternative community states with monocultures and polycultures of two native species of fish, least chub (Iotichthys phlegethontis) and Utah chub (Gila atraria) plus, introduced western mosquitofish (Gambusia affinis). We tested three hypotheses: (1) aquatic insect biomass will be greater than terrestrial insect biomass and thus, constitute a vital source of energy for terrestrial consumers (2) invasive mosquitofish will negatively impact the biomass of emerging aquatic insects, and (3) terrestrial consumers will negatively respond to decreased emerging aquatic insect biomass. Aquatic insects represented 79% of the flying insect community, and treatments with mosquitofish significantly reduced emergent aquatic insect biomass by 60% relative to the control without mosquitofish. Behavioral traits of invasive species are important, because mosquitofish most heavily affected insects that emerged during the day. Also, spiders that build horizontal webs were negatively correlated with decreasing aquatic insect biomass. Invasive mosquitofish can achieve very dense populations because of their high intrinsic rate of population increase, which can significantly disrupt the flow of energy between aquatic and terrestrial ecosystems, thereby reducing the energy available for terrestrial consumers.

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