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

BACKGROUND 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. OBJECTIVES We studied, in controlled laboratory conditions, the effect that light and dark cycles have on the efficiency of oviposition by Ae. aegypti females. METHODS Physiological assays were performed using synchronised eggs obtained from forced egg laying. The number and viability of eggs was analysed under three different light/dark regimes: LD12:12 (12 h of light and 12 h of dark), DD (constant darkness) and LL (constant light). FINDINGS and CONCLUSIONS Our results show that females prefer to lay their eggs in dark conditions, but maximising the number and viability of eggs requires the occurrence of a light/dark cycle. Ongoing research on this theme has the potential of contributing to the proposition of new strategies for control based on the failure of egg laying and hatching.

Variation in honey yield per hive of Africanized bees depending on the introducing time of young queens / Variação na produção de mel por colmeias de abelhas africanizadas em função da época de introdução de rainhas jovens

ABSTRACT: The objective of this research was to evaluate the honey production per hive and the egg laying rates of queens produced in 2007, 2008 and 2010. Thirty colonies initiated with a queen per colony at each climatic season were used during the three years. The years, started on January (summer), April (autumn), July (winter) and October (spring) and ended 12 months later, at the same periods related to each season of the later years. Honey supply were weighed before and after centrifugation to evaluate the quantity of the stored honey. Colonies with queens introduced during autumn and winter in the three years produced 57.2±6.0kg and 60.7±7.5kg of honey, respectively. In the first year of production activity, after the introduction of queens in the initial colonies, values were significantly higher than those obtained in colonies with queens introduced in the summer (39.3±7.6kg) and spring (41.8±3.7kg). Egg laying rates of queens were higher in spring (98.2±3.9%) and summer (88.4±7%), indicating greater food flow (flowerings) in these seasons compared to the averages in autumn (30.3±8.1%) and winter (24.5±7.2%). Produce and introduce queens of Africanized Apis mellifera in colonies initiated during autumn and winter was found to be economically feasible. Honey production of colonies initiated in these periods were higher and they had greater population stability in times of scarcity of flowerings.

RESUMO: O objetivo deste trabalho foi avaliar a produção de mel por colmeia e as taxas de postura de ovos das rainhas produzidas nos anos de 2007, 2008 e 2010. Foram utilizadas 30 colônias iniciadas com uma rainha/colônia por estação climática, durante os três anos. A cada ano, iniciou-se em: janeiro (verão), abril (outono), julho (inverno) e outubro (primavera) e encerrou-se doze meses depois, nos mesmos períodos referentes a cada estação dos anos posteriores. As melgueiras foram pesadas antes e depois da centrifugação para avaliar a quantidade do mel estocado. As colônias com rainhas introduzidas durante o outono e o inverno nos três anos produziram 57,2±6,0kg e 60,7±7,5kg de mel, respectivamente, no primeiro ano de atividade de produção após a introdução das rainhas nas colônias iniciais, valores significativamente superiores aos obtidos para as colônias com rainhas introduzidas no verão (39,3±7,6kg) e na primavera (41,8±3,7kg). As taxas de postura de ovos das rainhas foram mais altas na primavera e no verão (98,2±3,9% e 88,4±7%, respectivamente), indicando maior fluxo de alimento (floradas) nessas épocas, quando comparadas às médias do outono e inverno (30,3±8,1% e 24,5±7,2%, respectivamente). Constatou-se que é economicamente viável produzir rainhas e introduzir em colônias iniciais de Apis mellifera africanizada durante o outono e inverno. Além da produção de mel das colônias iniciadas nesses períodos ser superior, elas terão maior estabilidade populacional em épocas de escassez de floradas.

Oviposition preference of the neotropical brown stink bug Euschistus heros on artificial substrates of different colors / Preferência de oviposição do percevejo marrom Euschistus heros em substratos artificiais de diferentes cores

This study aimed to evaluate the oviposition preference of the Neotropical brown stink bug, Euschistus heros (F.) on artificial substrates of different colors (felt woven). For this, ten pairs of stink bugs were transferred into plastic pots. Each pot contained seven felts of 6x20 cm (100% polyester-atoxic) of different colors (white, black, blue, green, red, yellow and brown). The pots were evaluated daily for three weeks (21 days) being counted the number of eggs, clutches and eggs per clutch for each color of felt. The choice test was set in a completely randomized design. Data obtained was submitted to the analysis of variance and means were compared by Scott-Knott test at 5% probability. During the evaluation were produced 7074 eggs distributed in 977 clutches, accounting a mean of 7.06±0.67 eggs per clutch. Results indicated that females laid a significantly greater number of eggs (2380 and 1686) and a greater number of clutches (319 and 233) on the yellow and white felts, respectively, than on the remaining substrates. The substrates in color red, black and brown were the least preferred, and the colors blue and green were intermediate when compared with others. Therefore, the substrates colored yellow and white are suggested to be used in rearing E. heros in the laboratory.

Este estudo teve como objetivo avaliar a preferência para oviposição do percevejo marrom Euschistus heros (F.) em substratos artificiais de diferentes cores (feltros). Para isso, dez casais de percevejos foram transferidos para potes plásticos que continham sete feltros de 6x20 cm (100% poliéster atóxico) de cores diferentes (branco, preto, azul, verde, vermelho, amarelo e marrom). Os potes foram avaliados diariamente durante três semanas (21 dias), sendo contado o número de ovos, posturas e de ovos por postura para cada cor de feltro. O teste de preferência foi montado em um delineamento experimental inteiramente casualizado. Os dados obtidos foram submetidos à análise de variância e as médias comparadas pelo teste Scott-Knott a 5% de probabilidade. Durante a avaliação, foram produzidos 7.074 ovos, distribuídos em 977 posturas, contabilizando uma média de 7,06±0,67 ovos por posturas. Os resultados indicaram que as fêmeas ovipositaram um número significativamente maior de ovos (2380 e 1686) e de posturas (319 e 233) sobre os substratos de cores amarela e branca, respectivamente, do que nos demais substratos coloridos. Os feltros das cores vermelha, preta e marrom foram os menos preferidos, e as cores azul e verde foram intermediários, quando comparados aos demais. Assim, os substratos de cor amarela e branca são sugeridos para utilização na produção de ovos e criação de E. heros em laboratório.

Efeito do extrato aquoso do algodão de seda (Calotropis procera Aiton) sobre a eficiência reprodutiva do carrapato bovino / Effect of aqueous extract of silk cotton (Calotropis procera Ait. R.Br.) on the reproductive performance of Rhipicephalus microplus

O carrapato Rhipicephalus microplus é um dos principais parasitos dos rebanhos bovinos. Diferentes grupos de carrapaticidas sintéticos têm sido empregados para o controle desse ácaro, contudo, o uso constante desses produtos tem selecionado populações resistentes. Na tentativa de minimizar esses impactos tem-se buscado avaliar fitoterápicos para o controle desse parasito. Assim, objetivou-se analisar a eficácia in vitro do extrato aquoso do algodão de seda em diferentes concentrações no controle da postura e eclodibilidade dos ovos do R. microplus. Foram avaliados os efeitos das concentrações 1, 5, 10, 25, 50, 75 e 100% do extrato aquoso obtido juntamente com controles com água destilada ou com cipermetrina, 12,5 mg L-1, associada a organofosforado, 150 mg L-1, sobre a eficiência reprodutiva do carrapato. Foi realizado o biocarrapaticidograma sendo que a eficácia acaricida das concentrações 5, 25 e 100% foram superiores àquela observada para o produto comercial utilizado, que correspondeu a 93,98%, indicando a importância de futuras pesquisas para avaliar o potencial toxigênico e a eficácia in vivo dessa planta para o controle do R. microplus .

The tick Rhipicephalus microplus is one of the main parasites of bovine herds. Different groups of synthetic acaricides have been used to control this mite; however, the constant use of these products has selected resistant populations. In an attempt to minimize these impacts, researchers have tried to evaluate herbal remedies to control this parasite. Therefore, the aim of this study was to analyze the in vitro efficacy of aqueous extract of silk cotton at different concentrations to control the hatchability of R. microplus eggs. The effects of the concentrations 1, 5, 10, 25, 50, 75 and 100% aqueous extract together with controls with distilled water or with cypermethrin, 12.5 mg L-1, associated with organophosphate, 150 mg L-1, were assessed on the reproductive efficiency of the tick. Immersion test was performed and the acaricide efficacy of the 5, 25 and 100% concentrations were higher than that obtained for the commercial product, which corresponded to 93.98%, indicating the importance of further research to assess the toxigenic potential and the in vivo efficacy of this plant to control R. microplus .

Egg Laying Capacity of Haplorchis taichui (Digenea: Heterophyidae) in Humans

Quantitative fecal egg counts represented as the number of eggs per gram of feces (EPG) are generally a reliable parameter to estimate the worm burden of intestinal and hepatic parasitoses. Although Haplorchis taichui (Digenea: Heterophyidae) is one of the most common minute human intestinal flukes, little is known about the relationship between EPG and the actual worm burden in patients or the severity of the disease. In the present study, fecal samples were collected from 25 villagers in northern Thailand before and after praziquantel treatment. The EPG values of each participant were determined by the modified cellophane thick smear method, and adult worms were collected from the whole stool after the treatment. Eggs per day per worm (EPDPW) of H. taichui were estimated 82 from egg counts and expelled worms. The EPG was not well correlated with the worm burden, and a reverse correlation was observed between the EPDPW and the worm burden.

Oviposition behavior in wild Anastrepha obliqua (Macquart, 1835) (Diptera: Tephritidae): initial study of associative learning related to a protein source

In associative learning, experience enables an animal to associate a conditioned stimulus with some other meaningful stimulus producing either positive or negative effects. In this way, on a subsequent encounter, the response that was previously elicited only by the meaningful stimulus is then elicited by the conditioned stimulus as well. The aim of the present study was to investigate whether wild Anastrepha obliqua (Macquart, 1835) females are able to associate the presence of quinine sulphate (QS) in the composition of oviposition substrates with the presence of brewer's yeast (a protein source). First, the females were submitted to an experience period with artificial substrate containing brewer's yeast + QS (YQS substrate). After this period, the females were allowed to choose between substrates with or without QS. In one group, the substrates contained brewer's yeast (YQS x Y substrates); in the other group, the substrates contained only agar (AQS x A substrates). In the YQS x Y choice situation, a smaller quantity of eggs was found on YQS substrates, only on the first choice day. In the AQS x A choice situation, there was no preference for one of the substrates on each of the three choice days. However, we think it is too early to state that A. obliqua females are not able to perform the association in question. These flies show a high behavioral flexibility concerning their oviposition behavior strategies. Besides, this behavior, in this species, includes several stages. Based on it, possible explanations for the results are discussed in this study.

Seleção de sítios de oviposição em anuros (Lissamphibia) / Oviposition site selection in anurans (Lissamphibia)

A seleção de sítios de oviposição é uma forma de seleção de hábitat em que as fêmeas escolhem o micro-ambiente de desova procurando maximizar o sucesso reprodutivo. Nesta revisão, compilamos as principais conclusões de estudos sobre seleção de sítios de oviposição tendo os anuros como modelo. Na literatura, podemos reconhecer três linhas principais de investigação: 1) análise de múltiplos fatores em hábitat natural- no ambiente de reprodução, sítios com ovos e girinos são comparados com locais não utilizados com base em fatores abióticos e bióticos com potencial de influenciar a escolha da fêmea; 2) experimentos controlados com poças dispostas em blocos replicados simulando sítios potenciais de oviposição com diferenças na qualidade e 3) quantificações de eventos reprodutivos e experimentos de manipulação em ambiente natural. Fêmeas de várias espécies de anuros selecionam sítios de oviposição mais favoráveis à sobrevivência e desenvolvimento dos ovos e girinos. O comportamento de escolha depende da abundância e qualidade relativa dos locais potenciais de desova e da capacidade de discriminação da fêmea. Em geral, as escolhas das fêmeas respondem aos principais riscos à sobrevivência e desempenho da prole, porém apresentam eficiência relativa e perdas parciais ou totais de desovas e girinos são ocasionadas, principalmente, por fatores de mortalidade direta como dessecação e predação. Os mecanismos sensoriais que elas utilizam para discriminar as condições do ambiente de reprodução ainda são praticamente desconhecidos. Além de afetar o sucesso reprodutivo dos parentais, o comportamento de escolha pode influenciar na dinâmica de populações e estrutura de comunidades ao promover a segregação de hábitat entre espécies competidoras ou entre espécies-presa e seus predadores.

Oviposition site selection is a kind of habitat selection in which the females choose egg-laying sites that maximize their reproductive success. In the present review, we compiled the main conclusions of major studies on this theme that used frogs as model organisms. In the literature, three main lines of investigations were recognized: 1) multiple factor analyses in natural habitats- within the breeding site, places with eggs/tadpoles are compared with unused sites, testing several abiotic and biotic factors that could potentially influence female's choice; 2) experiments with pools arranged in replicated blocks (treatments/control) to simulate oviposition sites differing in quality and 3) quantification of reproductive events associated with experimental manipulations in the field. Effectively, females of several frog species select oviposition sites more favorable to survival and development of eggs and tadpoles. In general, the female choice depends on the abundance and quality of potential egg-laying sites and on her discriminatory ability. Female choices usually mirror the main risks to survival and growth of the offspring, but discriminatory power is not absolute and partial or total losses of clutches and tadpoles may occur, most of them resulting from desiccation and predation. The sensory mechanisms that females use to discriminate the conditions of potential oviposition sites remain poorly known and unexplored. Besides affecting the parental reproductive success, the selective behavior potentially influence population dynamics and community structure by promoting habitat segregation among competitive species or prey-species and their predators.

Prevalencia de eimeria spp: En gallinas ponedoras de granjas pertenecientes a tres municipios del estado trujillo, venezuela / Prevalence of eimeria spp: In egg-laying hens of farms belonging to three municipalities of trujillo state, venezuela

Se realizó un estudio con la finalidad de determinar la prevalencia de Eimeria spp. en granjas de gallinas ponedoras ubicadas en los municipios Boconó, Pampán y Carvajal del estado Trujillo, Venezuela. Para ello fue seleccionada una población de 8.500 ponedoras evaluándose una muestra de 382, a través de la técnica de McMaster, obteniéndose una prevalencia de 17,02%. Se reportó la presencia de Ascaridia galli con una prevalencia de 5,24%. Se encontraron diferencias significativas en la distribución porcentual de las eimerias en los diferentes Municipios, centrándose el mayor porcentaje en el municipio Pampàn (P = 0,0000). El mayor porcentaje de las muestras positivas presentaron cargas de entre 50 y 200 ooquistes (P = 0,0000). Se evidenciaron las mayores tasas de infección en pisos de tierra (P £ 0,0055) y en la época lluviosa del año (P £ 0,0055).

A study was carried out with the purpose of determining the prevalence of Eimeria spp in farms of egg-laying hens located in the Municipalities of Boconó, Pampán and Carvajal. Trujillo, Venezuela. For an egg-laying hens population of 8,500 it was selected a sample of 382, of which was evaluated through the technique of McMaster. A prevalence of 17.02% was obtained. Significant differences in the percentage distribution of the Eimeria spp. were found in the different Municipalities, being centered the biggest percentage in the Municipality of Pampán (P = 0.0000). The biggest percentage in the positive samples presented loads of between 50 and 200 oocysts per gram of faces (P = 0.0000). The biggest infection rates were evidenced in earth floors (P £ 0.0055) and in the rainy time of the year (P £ 0.0055).

Substituição natural de rainhas fisogástricas e distância de vôo dos machos em Tiuba (Melipona compressipes fasciculata Smith, 1854) e Uruçu (Melipona scutellaris Latreille, 1811) (Apidae, Meliponini) / Natural substitutions of queens and flight distance of males in tiuba (Melipona compressipes fasciculata Smith, 1854) and uruçu (Melipona scutellaris Latreille, 1811) (Apidae, Meliponini)

Este trabalho relata detalhes da vida reprodutiva de duas espécies de abelhas sem ferrão. Rainhas velhas de Melipona compressipes fasciculata, no Maranhão, morrem e são substituídas com sucesso em todos os meses. Rainhas de Melipona scutellaris, trazidas de Lençóis (BA - nordeste do Brasil) para Uberlândia (MG, centro-sudeste do Brasil) morreram durante todos os meses e não mostraram a existência de trimestre preferencial para as novas rainhas iniciarem postura. Quarenta machos de M. scutellaris, após serem marcados no tórax e libertados em grupos de 10 a 100, 400, 800 e 1000 metros do meliponário, tiveram seus retornos observados. Todos os machos libertados a 100 e 400 metros regressaram ao meliponário, 7 de 10 machos e 2 de 10 machos retornaram de 800 e 1000 metros, respectivamente. Os machos esperam constantemente pela saída de uma rainha virgem, próximos às colônias órfãs, o que indica que a maioria das rainhas é inseminada próximo aos seus ninhos, portanto, a dispersão dos genes depende do vôo dos machos e da distância de enxameagem para ocupação de uma cavidade para o novo ninho.

This work reports on the reproductive life of the stingless bees (Meliponini). Old queens of Melipona compressipes fasciculata in Maranhão State, Brazil die and are successfully substituted by new ones in all months. Queens of Melipona scutellaris from Lençois (BA - northeastern Brazil) brought to Uberlândia (Central South eastern Brazil) died during all months, and there are no months where new queens are more able to begin egg laying. Forty males of M. scutellaris were marked in the thorax and released in groups of 10 at 100, 400, 800 and 1000 meters from the meliponary and their return to it was observed. All males released at 100 to 400 meters returned, 7 out of 10 and 2 out of 10 males returned respectively from 800 and 1000 meters. Males are constantly waiting for a virgin queen next to orphan colonies, the majority of the queens is inseminated in near the hive, therefore, gene dispersion depends more upon the males and of the occupation of a new cavity for nest.

Communal egg laying by Gonatodes humeralis (Sauria, Gekkonidae) in Manaus primary and secondary forest areas

Communal nesting has been registered for a number of lizard species at different sites. Here it is described communal egg laying of Gonatodes humeralis at different sites near and in human buildings in the period between 1990 and 1998. All these communal nests have been found in the dry season, between April and July, suggesting that the nests of are more common in this season, when the activity of their predators is less intense and the reduction of humidity diminish the decomposition action of the fungi that may kill the eggs.

Desovas comunais tem sido registradas para inúmeras espécies de lagartos em diferentes regiões. Neste estudo, estão descritas desovas comunais de Gonatodes humeralis em diferentes localidades próximas, no interior de construções humanas no período entre 1990 e 1998. Todas estas desovas comunais foram encontradas na estação seca, entre abril e julho, sugerindo que estas desovas são mais comuns neste período, quando a atividade dos predadores é menos intensa e a redução da umidade diminui a ação decompositora dos fungos que pode matar os ovos.

Within- and among-population variation in oviposition preference of urea-supplemented food in Drosophila melanogaster.

Oviposition preference for urea-supplemented food was assayed by simultaneous choice trials on five pairs of closely related laboratory populations of Drosophila melanogaster. Each pair of populations had been derived from a separate ancestral population about 85 generations prior to this study. One population in each pair had been subjected to selection for larval tolerance to the toxic effects of urea; the other population served as a control. Considerable variation in oviposition preference was seen both within and among populations, with four of the ten populations showing a significant mean preference for urea-supplemented food. The degree of specificity shown by individual females was surprisingly high, leading to a bi-modal distribution of oviposition preference in some populations. Overall, selection for larval tolerance to urea did not significantly affect oviposition preference. However, the data indicated that pair-wise comparisons between randomly selected populations from the two larval selection regimes would lead to a range of possible outcomes, suggesting, in several cases, that selection for larval urea tolerance had led to significant differentiation of adult oviposition preference for urea in one or the other direction. The results, therefore, highlight the importance of population level replication and caution against the practice, common in ecological studies, of assaying oviposition preference in two populations that utilize different hosts in nature, and then drawing broad evolutionary inferences from the results.