Abstract:

The effect of multiple immersions on Haemagogus janthinomys, Haemagogus leucocelaenus, Aedes albopictus and Ochlerotatus terrens eggs was studied. Eggs were collected in April, June, October and December of 2011 in Minas Gerais, Brazil. Most of the Aedes and Ochlerotatus eggs hatched upon the first immersion, while Haemagogus eggs showed a varied instalment hatching response. The number of immersions required for hatching increased for eggs collected closer to the dry winter season.

Author affiliation: Alencar, Jerónimo. Instituto Oswaldo Cruz; Brasil

Author affiliation: Gleiser, Raquel M.. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Morone, Fernanda. Instituto Oswaldo Cruz; Brasil

Author affiliation: Mello, Cecília Ferreira de. Instituto Oswaldo Cruz; Brasil

Author affiliation: Silva, Júlia dos Santos. Instituto Oswaldo Cruz; Brasil

Author affiliation: Serra Freire, Nicolau Maués. Instituto Oswaldo Cruz; Brasil

Author affiliation: Guimarães, Anthony Érico. Instituto Oswaldo Cruz; Brasil

Abstract:

El presente trabajo de Tesis analizó diversos aspectos de la reproducción en dos especies de vinchucas, Rhodnius prolixus y Triatoma infestans, con un enfoque comportamental a partir del estudio de diferentes eventos puntuales del proceso reproductivo. En primer lugar, se analizaron en detalle las señales de estridulación producidas frente a una perturbación mecánica artificial y como respuesta de rechazo a los intentos de cópula de los machos en hembras de R. prolixus. Al igual que ocurre en T. infestans, se trata de dos señales diferentes que actúan en dos contextos comportamentales distintos. Se analizó en forma cuantitativa y controlada la importancia de la cópula tanto en la fecundidad, medida como número de huevos puestos, como en la fertilidad, porcentaje de eclosiones, para la especie T. infestans. Se verificó una distribución agrupada de los huevos puestos por hembras de R. prolixus, aunque no pudo hallarse ninguna clave química responsable de tal comportamiento. Se determinó la preferencia térmica para la oviposición en relación con la temperatura preferida para permanecer en R. prolixus, analizando si buscan activamente la temperatura del sitio de oviposición. Por último, se demostró la ritmicidad circadiana endógena de la eclosión del huevo en R. prolixus.

The present Thesis work analyses some aspects of the reproduction in two species of blood-sucking bugs, Rhodnius prolixus and Triatoma infestans, by means of a behavioural approach, and focussing on particular aspects of the reproductive process. First, stridulatory signals evoked by a mechanical perturbation or as a response of females to copulatory attempts performed by males were analysed in detail. As in T. infestans, they appear as two distinct signals acting in two different behavioural contexts. Second, quantitative measures of the role of the copula on fecundity, i.e., the number of eggs laid, and fertility, i.e., number of hatched eggs, were performed in T. infestans. An aggregated distribution of laid eggs was evinced in R. prolixus, although this behaviour does not seem to be mediated by chemical signals. Besides, the thermopreference for oviposition in relation to the temperature preference of R. prolixus was studied. Finally, the existence of an endogenous circadian clock controlling egg hatching was demonstrated for R. prolixus.

Author affiliation: Schilman, Pablo Ernesto. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

Aedes (Ochlerotatus) albifasciatus (Macquart) has the capacity to proliferate in different kinds of climates within its distribution range in South America. With the aim of studying local thermal adaptations of eggs, we exposed egg stocks from two climatically different localities: temperate humid pampa (Buenos Aires) and cold arid Patagonian (Sarmiento), to freezing conditions and then evaluated the effect on some features at this level. First, we thermally described the substrate where this species lays its eggs in the arid region. A typical thermal condition during winter was 10 h at -12° C. Second, we evaluated the effect of freezing on primary hatching (vs total hatching) and embryo survival. We also compared the proportion of embryonated eggs from both populations. The proportions of embryonated eggs were not different between localities, with averages of 78% and 83% in Sarmiento and Buenos Aires, respectively. Survival was equally successful after freezing in the two localities with an average range between 94-99%. Whether or not the eggs from Buenos Aires and Sarmiento were under freezing conditions, hatching was more than 98% after the first flooding. The results suggest that eggs of Ae. albifasciatus from Sarmiento and Buenos Aires have the same ability to survive at extreme temperatures (<0° C), showing a regional thermal adaptation rather than a local one.

Author affiliation: Garzón, Maximiliano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Author affiliation: Jensen, Oscar. Provincia del Chubut. Ministerio de Salud. Departamento de Investigación En Salud; Argentina

Author affiliation: Schweigmann, Nicolas Joaquin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina