Seven species of planktonic microcrustacea were identified from the North Texas State University Golf Course Pond. Total adult microcrustacean community density, biomass and biocontent, and seasonal cycles of each species were compared with northern populations. Species diversity and evenness indices were highest in summer and lowest in spring. Variations in microcrustacean density showed a positive correlation with density of phytoplankton. Temperature had a direct effect on metabolic rates of two species of copepods. Metabolic rates of pond species were lower at common temperatures than those of northern populations. An estimate of annual energy flow through the pond ecosystem showed cladocerans contributed the greater percentage of total energy to the next trophic level.

Les zones littorales à macrophytes ont un rôle fonctionnel important dans les hydrosystèmes fluviaux. Outre leur forte productivité, ces milieux se caractérisent également par une forte biodiversité. Cependant, les liens pouvant exister entre hétérogénéité spatiale, biodiversité et flux de matière restent encore peu connus. En milieu aquatique, les microcrustacés représentent un maillon clef entre les microorganismes eucaryotes, qui sont les principaux producteurs d’acide gras polyinsaturés (AGPI), et le compartiment piscicole. Dans ce travail de thèse, nous avons donc cherché à savoir comment la diversité des cladocères rencontrée dans une zone littorale à macrophytes pouvait affecter le transfert des AGPI dans les réseaux trophiques. L’approche vers laquelle s’est orienté ce travail combine à la fois des études menées en milieu contrôlé, permettant des expériences de nutrition, ainsi que des études menées en milieu naturel. Cette double approche permet de faciliter l’interprétation des résultats issus des analyses lipidiques, isotopiques et isotopiques de composés spécifiques. Nos résultats montrent ainsi qu’il n’existe pas de variabilité dans les capacités d’accumulation et de bioconversion des AGPI chez les cladocères coexistant dans une zone littorale à macrophytes. D’après ces résultats, il semble donc que le principal facteur influençant la variabilité des transferts d’AGPI vers le compartiment piscicole soit la stratégie alimentaire et le compartiment trophique exploité par les différentes espèces de microcrustacés. En effet, outre le seston, notre étude montre que certaines espèces de cladocères rencontrées en zone littorale sont capables d’exploiter l’épiphyton et le neuston. Les analyses lipidiques mettent de plus en évidence, que la diversité des compartiments trophiques exploités s’accompagne d’une variabilité d’apports en AGPI. Dans notre étude, l’épiphyton est ainsi significativement plus concentré en AGPI que le seston. A l’interface air-eau, le neuston se caractérise de plus, par une forte accumulation de matière organique d’origine allochtone qui, dans le cas d’une pluie de pollen, représente une source de carbone et d’AGPI non négligeable pour certaines espèces de microcrustacés. Dans les zones littorales à macrophytes, la complémentarité des espèces de cladocères entraine donc une utilisation plus complète des ressources. La diversité des compartiments trophiques, associée à la diversité des microcrustacés, permet donc probablement une optimisation du transfert des AGPI vers les niveaux trophiques supérieurs. / Areas with littoral macrophytes play an important functional role in freshwater systems. In addition to the high productivity recorded in such areas, they also shelter a high diversity of organisms. However, possible links between spatial heterogeneity, biodiversity and energy pathways are still poorly known. As they constitute the major link between microorganisms and species higher in the food web, microcrustaceans play a key role in the transfer of polyunsaturated fatty acids (PUFA) to organisms at higher trophic levels. In this study, we wanted to assess if microcrustaceans diversity encountered in macrophytes littoral zones would lead to a variability of PUFA transfer in the food web. This work combined controlled conditions experiment and studies run in natural environments in order to help the interpretation of results from lipid analysis, isotopic analysis and fatty acid isotope analysis. Our results indicate that there are no differences of PUFA concentrations between cladocerans from a macrophyte littoral zone when they were exposed to the same pool of dietary PUFA. Hence, in heterogeneous feeding habitats such as macrophytes zones where these cladocerans often co-exist, foraging behavior of cladoceran species more than differences of metabolism may be crucial for determining PUFA transfer to upper trophic levels. In addition to seston, our study shows indeed that some cladoceran species are able to forage on the epiphytic and neustonic compartments. Lipid analyses highlight moreover that the diversity of trophic compartments lead to a variability of PUFA inputs to primary consumers. In our study, the epiphytic compartment is indeed significantly more concentrated in PUFA than seston. At the air-water interface, neuston is moreover characterized by important allochthonous organic matter accumulation. During a pollen rain, this organic matter represents an important source of carbon and PUFA for some microcrustacean species. In macrophytes littoral zones, cladocerans complementarity leads to a more complete use of PUFA sources. The association of trophic compartment diversity and microcrustacean diversity probably allows an optimization of PUFA transfer to higher trophic levels.

Made available in DSpace on 2016-06-02T19:31:57Z (GMT). No. of bitstreams: 1 3764.pdf: 1429773 bytes, checksum: 4073170af6df253bf6cb50f4e03c4a19 (MD5) Previous issue date: 2011-07-01 / Universidade Federal de Sao Carlos / The hatchery is now the main obstacle of aquaculture. The live food, especially zooplankton, is essential in early life stages of fish. However, there are difficulties in obtaining enough biomass. The Anostraca Dendrocephalus brasiliensis, known as branconeta, has great potential of use in national aquaculture. In this study, it was performed experiments of food selectivity and secondary production with fingerlings of matrinxã (Brycon cephalus) and pintado-da-amazônia, a hybrid between Pseudoplatystoma corruscans and Leiarius marmoratus, using D. brasiliensis and other species of zooplankton as food. Food selectivity results were evaluated using the Ivlev selectivity index and the coefficient of food Paloheimo. For both species, the indexes of the juveniles indicated a preference by D. brasiliensis in comparison to zooplankton. Secondary production values were better when matrinxã was fed with Artemia plus artificial food; there was no significant difference to fish fed with branconeta. For pintado-da-amazônia, the highest production was obtained from branconeta treatment. So, the selectivity for D. brasiliensis is positive, once it was accepted by both species, without rejection. The results allow us to assert that the use of D. brasiliensis is suitable for the cultivation of both species. / A larvicultura é hoje o principal entrave da aqüicultura. O alimento vivo, em especial zooplanctônico, é essencial nas fases jovens de peixes. No entanto, há dificuldades em se obter biomassa suficiente. O Anostraca Dendrocephalus brasiliensis, conhecido como branconeta, tem grande potencial de utilização na aqüicultura nacional. No presente estudo, foram realizados estudos de seletividade alimentar e produção secundária com alevinos de matrinxã, Brycon cephalus, e pintado-da-amazônia, um híbrido entre Pseudoplatystoma corruscans e Leiarius marmoratus, utilizando-se D. brasiliensis e outras espécies zooplanctônicas como alimento. Os resultados de seletividade alimentar foram avaliados utilizando-se o índice de seletividade de Ivlev e o coeficiente alimentar de Paloheimo. Para as duas espécies, os índices apontaram preferência dos alevinos por D. brasiliensis frente ao zooplâncton. Os ensaios de produção secundária com matrinxã resultaram em melhor rendimento com ração e Artemia, sem diferença significativa com branconeta. Para o pintado-da-amazônia, a maior produção foi obtida com branconeta. Podemos dizer que a seletividade para D. brasiliensis é positiva, aceita por ambas as espécies, sem rejeição. Os resultados nos permitem afirmar que o uso de D. brasiliensis é apropriado no cultivo de ambas as espécies.