The Effects of Infection on Mosquito Rhythmic Behavior

Most organisms live in a rhythmic world, where daily environmental variation has a profound effect on their behavior and physiology. In addition to abiotic influence, interactions with other organisms that have their own particular cycles are also part of circadian rhythm formation. In this chapter, we present aspects of the biology of mosquito vectors, more precisely Aedes aegypti, which is a vector of arboviruses of great epidemiological importance, like dengue, Zika, and chikungunya. The successful transmission of the virus depends on the coordination of several behavioral and physiological traits involved in the virus-vector-host interaction. Thus, understanding the mechanisms of endogenous control of rhythmic traits of the mosquito vector and the impact that both environmental variation and virus infection can have on this regulation is key for a reliable estimate of the vectorial capacity. We discuss the infection-driven changes in traits used to calculate parameters of the vectorial capacity, and finally, we review the current knowledge on the molecular mechanisms underlying vector rhythmic behavior and the potential cellular targets of arbovirus infection

A Sex-Ratio Meiotic Drive System in Drosophila Simulans. I: An Autosomal Suppressor

Sex ratio distortion (sex-ratio for short) has been reported in numerous species such as Drosophila, where distortion can readily be detected in experimental crosses, but the molecular mechanisms remain elusive. Here we characterize an autosomal sex-ratio suppressor from D. simulans that we designate as not much yang (nmy, polytene chromosome position 87F3). Nmy suppresses an X-linked sex-ratio distorter, contains a pair of near-perfect inverted repeats of 345 bp, and evidently originated through retrotransposition from the distorter itself. The suppression is likely mediated by sequence homology between the suppressor and distorter. The strength of sex-ratio is greatly enhanced by lower temperature. This temperature sensitivity was used to assign the sex-ratio etiology to the maturation process of the Y-bearing sperm, a hypothesis corroborated by both light microscope observations and ultrastructural studies. It has long been suggested that an X-linked sex-ratio distorter can evolve by exploiting loopholes in the meiotic machinery for its own transmission advantage, which may be offset by other changes in the genome that control the selfish distorter. Data obtained in this study help to understand this evolutionary mechanism in molecular detail and provide insight regarding its evolutionary impact on genomic architecture and speciation.Organismic and Evolutionary Biolog

Genetic and morphological variation in populations of Zaprionus indianus (Diptera: Drosophilidae)

Resumo: A espécie Zaprionus indianus expandiu sua distribuição geográfica recentemente, a partir da invasão do continente sul-americano. O primeiro registro data de apenas seis anos, e acredita-se que a origem seja sul-africana. Hoje, indivíduos dessa espécie são encontrados numa amplitude latitudinal de 35o, do Uruguai a Belém (Brasil). A chegada de Z. indianus no Brasil apresenta uma oportunidade rara de se estudar um evento de invasão desde seu início. O estudo de características fisiológicas, morfológicas e genéticas de populações brasileiras pode ajudar a construir hipóteses para o sucesso de Z. indianus nas etapas de invasão, além de indicar o potencial para evolução e diferenciação fenotípica. Um aspecto fisiológico estudado nesta tese foi a condição reprodutiva em machos que foram submetidos a extremos de temperatura ao longo de seu desenvolvimento. O estresse térmico causa esterilidade nos machos e a investigação dos limites (superior e inferior) da curva de fertilidade relativa à temperatura, complementa os dados de viabilidade na caracterização do potencial de ocupação de áreas novas por espécies cosmopolitas. Quanto à morfologia, um aspecto estudado foi o dimorfismo sexual no número de cerdas abdominais em uma população africana. Dimorfismo sexual para este caráter foi observado em várias espécies em estudos anteriores, embora padrões diferentes tenham sido encontrados. Nesta tese o padrão observado em Z. indianus foi comparado com o de outra espécie cosmopolita, Drosophila melanogaster. Um terceiro ponto abordado nesta tese foi a investigação de 10 populações brasileiras quanto à variação fenotípica (tamanho e forma da asa). Além das diferenças entre populações, uma abordagem interessante é o quanto de variação está presente dentro de cada população. Ainda, é importante saber o quanto dessa variação é herdável para estimarmos qual a capacidade evolutiva da população. O estudo revelou a ocorrência de alta variabilidade fenotípica dentro e entre populações, além de variação genética aditiva suficiente para promover a evolução de caracteres relacionados à forma da asa ;;Abstract: The species Zaprionus indianus has recently expanded its geographical distribution with the invasion of the South American continent. The first record dates of only six years, and the origin is probably the South Africa. Nowadays, individuals of this species can be found in a latitudinal range of 35o, from Uruguai to Belém (Brazil). The arrival of Z. indianus in Brazil presents a rare opportunity of studying an event of invasion from its beginning. The study of physiological, morphological and genetic traits in Brazilian populations may contribute to generate hypothesis for the success of Z. indianus in the stages of invasion. Also, it may indicate the potential for evolution and phenotypic differentiation. One physiological trait studied in the current thesis was the relationship of fertility and the temperature of development. Extreme temperatures cause sterility in males and the study of the limits (upper and lower) of the fertility curve complements the data on viability for the characterization of the potential of cosmopolitan species to occupy new areas. One morphological character studied was the sexual dimorphism for the number of abdominal bristles in one African population. A significant sexual dimorphism for this trait was observed in several species in previous studies, though different patterns have been found. In the current work the pattern observed in Z. indianus was compared to the pattern for another cosmopolitan species, Drosophila melanogaster. The third approach of this thesis was the study of the phenotypic variation (size and shape of the wing) present in 10 Brazilian populations. Besides the differences among populations, an interesting approach is the amount of variation present within each population. Also, it is important to know the proportion of this variation that is heritable, which allows an estimate of the evolutionary potential of the population. This study revealed the occurrence of high phenotypic variability within and between populations. In addition, enough additive genetic variation exists to promote the evolution of traits related to the shape of the win

The influence of a light and dark cycle on the egg laying activity of Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae)

Submitted by Sandra Infurna ([email protected]) on 2018-05-03T13:28:58Z No. of bitstreams: 1 luana_farnesi_etal_IOC_2018.pdf: 359861 bytes, checksum: c84c8c7e3992c10bdee743d11377bfd4 (MD5)Approved for entry into archive by Sandra Infurna ([email protected]) on 2018-05-03T13:38:07Z (GMT) No. of bitstreams: 1 luana_farnesi_etal_IOC_2018.pdf: 359861 bytes, checksum: c84c8c7e3992c10bdee743d11377bfd4 (MD5)Made available in DSpace on 2018-05-03T13:38:07Z (GMT). No. of bitstreams: 1 luana_farnesi_etal_IOC_2018.pdf: 359861 bytes, checksum: c84c8c7e3992c10bdee743d11377bfd4 (MD5) Previous issue date: 2018Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular de Insetos. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular de Insetos. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular de Insetos. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular de Insetos. Rio de Janeiro, RJ, Brasil / Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Rio de Janeiro, RJ, Brasil.The epidemiological importance of the mosquito Aedes aegypti as a vector of multiple human pathogens has generated a growing number of studies on the physiology and behaviour of its blood-feeding females. The activity of oviposition is one of the critical elements contributing to the expansion of Ae. aegypti's populations. Although there is a vast literature about oviposition behaviour, significant specific knowledge about egg viability and female fertility under light and dark conditions is still lacking

Locomotor activity in males of Aedes aegypti can shift in response to females’ presence

Abstract Background The study of physiological and behavioral traits of mosquito vectors has been of growing relevance for the proposition of alternative methods for controlling vector-borne diseases. Despite this, most studies focus on the female’s traits, including the behavior of host seeking, the physiology of disease transmission and the site-choice for oviposition. However, understanding the factors that lead to males’ reproductive success is of utmost importance, since it can help building new strategies for constraining population growth. Male behavior towards mating varies widely among species and the communication between males and females is the first aspect securing a successful encounter. Here we used an automated monitoring system to study the profile of locomotor activity of Aedes aegypti males in response to female’s presence in an adapted confinement tube. We propose a new method to quantify male response to the presence of females, which can be potentially tested as an indicator of the success of one male in recognizing a female for mating. Results Locomotor activity varies in daily cycles regulated by an endogenous clock and synchronized by external factors, such as light and temperature. Our results show the previously described startle response to light, which is displayed as a steep morning activity peak immediately when lights are on. Activity drops during the day and begins to rise again right before evening, happening about 1.5 h earlier in males than in females. Most interestingly, males’ activity shows a double peak, and the second peak is very subtle when males are alone and relatively more pronounced when females are present in the confinement tubes. The switch in the peak of activity, measured by the herein suggested Peak Matching Index (PMI), was significantly different between males with and without females. Conclusions The adapted monitoring system used here allowed us to quantify the response of individual males to nearby females in terms of the extent of the activity peak displacement. In this direction, we created the peak matching index (PMI), a new parameter that we anticipate could be interpreted as the inclination of males to respond to females’ presence, and further tested as an indicator of the potential for finding females for mating