Entomological investigations in a focus of dengue transmission in Cairns, Queensland, Australia, by using the sticky ovitraps

Sticky ovitraps (patent pending) were used to sample female Aedes aegypti (L.) weekly in a focus of dengue activity in Cairns, Queensland, Australia. In February 2003, transmission of dengue virus serotype 2 began in the suburb of Parramatta Park, peaking in mid-March 2003. This suburb features many older, unscreened houses with high populations of Ae. aegypti. Highest densities (2-3.5 females per trap per week) were obtained during peak dengue transmission (January and February) before mosquito control was initiated. Beginning in late March, female Ae. aegypti collected in sticky ovitraps were tested for dengue viral RNA by using a TaqMan reverse transcription-polymerase chain reaction assay. Dengue viral RNA was detected in six pools of Ae. aegypti collected in late March. The highest minimum infection rate was 116/1000 mosquitoes. After the initiation of larval control (containers treated with S-methoprene or lambda-cyhalothrin) and adult control (interior harborage sites sprayed with lambda-cyhalothrin) in early March, trap collections dropped to

Parasitization of Manduca sexta larvae by the parasitoid wasp Cotesia congregata induces an impaired host immune response

During oviposition, the parasitoid wasp Cotesia congregata injects polydnavirus, venom, and parasitoid eggs into larvae of its lepidopteran host.. the tobacco hornworm, Manduca sexta. Polydnaviruses (PDVs) suppress the immune system of the host and allow the juvenile parasitoids to develop without being encapsulated by host hemocytes mobilized by the immune system. Previous work identified a gene in the Cotesia rubecula PDV (CrV1) that is responsible for depolymerization of actin in hemocytes of the host Pieris rapae during a narrow temporal window from 4 to 8 h post-parasitization. Its expression appears temporally correlated with hemocyte dysfunction. After this time, the hemocytes recover, and encapsulation is then inhibited by other mechanism(s). In contrast, in parasitized tobacco hornworm larvae this type of inactivation in hemocytes of parasitized M. sexta larvae leads to irreversible cellular disruption. We have characterized the temporal pattern of expression of the CrV1-homolog from the C. congregata PDV in host fat body and hemocytes using Northern blots, and localized the protein in host hemocytes with polyclonal antibodies to CrV1 protein produced in P. rapae in response to expression of the CrV1 protein. Host hemocytes stained with FITC-labeled phalloidin, which binds to filamentous actin, were used to observe hemocyte disruption in parasitized and virus-injected hosts and a comparison was made to hemocytes of nonparasitized control larvae. At 24 h post-parasitization host hemocytes were significantly altered compared to those of nonparasitized larvae. Hemocytes front newly parasitized hosts displayed blebbing, inhibition of spreading and adhesion, and overall cell disruption. A CrV1-homolog gene product was localized in host hemocytes using polyclonal CrV1 antibodies, suggesting that CrV1-like gene products of C. congregata's bracovirus are responsible for the impaired immune response of the host. (C) 2005 Elsevier Ltd. All rights reserved.

Refinement of a cell line based artificial diet for rearing the parasitoid wasp, Trichogramma pretiosum

An artificial diet incorporating insect cells originally developed for Trichogramma australicum Girault (Hymenoptera: Tricho-grammatidae) was successfully used to rear Trichogramm pretiosum Riley (Hymenoptera: Trichogrammatidae). To refine the diet, individual components were removed. Chicken egg yolk and the insect cells were identified as the most important components for T. pretiosum development. Their removal resulted in few pupae and no adults. Removal of Grace's insect medium, a common component of artificial diets, was found to markedly improve the development of T pretiosum, producing 60% larva to pupa transition and 19% pupa to adult transition. There was no significant difference in T pretiosum development on diets in which milk powder, malt powder or infant formula were interchanged, despite differences in nutrient composition. The use of yeast extract resulted in significantly higher survival to the adult stage when compared with yeast hydrolysate enzymatic and a combination of yeast extract and yeast hydrolysate enzymatic. Comparison of four antimicrobial agents showed the antibacterial agent Gentamycin and the antifungal agent Nystatin had the least detrimental effect on T pretiosum development. The use of insect cell line diets has the potential to simplify artificial diet production and significantly reduce T pretiosum production costs in Australia compared to diets using insect hemolymph or the use of natural or factitious hosts. (c) 2005 Elsevier Inc. All rights reserved.

Helicoverpa armigera (Hubner): can wheat stubble protect cotton plants against attack?

When investigating strategies for Helicoverpa armigera (Hubner) control, it is important to understand oviposition behaviour. Cotton (Gossypium hirsutum) was sown into standing wheat (Triticum astivum L.) stubble in a closed arena to investigate the effect of stubble on H. armigera moth behaviour and oviposition. Infrared cameras were used to track moths and determine whether stubble acted as a physical barrier or provided camouflage to cotton plants, thereby reducing oviposition. Searching activity was observed to peak shortly before dawn (03:00 and 04:00 h) and remained high until just after dawn (4 h window). Moths spent more time resting on cotton plants than spiralling above them, and the least time flying across the arena. While female moths spent more time searching for cotton plants growing in wheat stubble, the difference in oviposition was not significant. As similar numbers of eggs were laid on cotton plants with stubble (3.5/plant SE +/- 0.87) and without stubble (2.5/plant SE +/- 0.91), wheat stubble does not appear to provide camouflage to cotton plants. There was no significant difference in the location of eggs deposited on cotton plants with and without stubble, although more eggs were laid on the tops of cotton leaves in wheat stubble. As the spatial and temporal distribution of eggs laid on the cotton plant is a crucial component of population stability, eggs laid on the upper side of leaves on cotton plants may be more prone to fatalities caused by environmental factors such as wind and rain. Therefore, although stubble did not influence the number of eggs laid, it did affect their distribution on the plant, which may result in increased mortality of eggs on cotton plants sown into standing wheat stubble.

Confirmation of the existence of alloparasitoids in nature - host relationships of an Australian Coccophagus species that parasitizes mealy bugs

Heteronomous hyperparasitoids are parasitic wasps with sex-related host relationships that are unique to a group of genera in the chalcidoid family Aphelinidae. Females are primary parasitoids of various sedentary bugs (mainly, scale insects, mealy bugs, and whiteflies). Males, in contrast, are hyperparasitic, and they frequently develop at the expense of female conspecifics. Alloparasitoids constitute a special category of heteronomous hyperparasitoids, for their males never develop through female conspecifics. The existence of alloparasitic host relationships and the utility of the category 'alloparasitoid' have both been questioned. Here, we present results that confirm the existence of the alloparasitic way of life among heteronomous aphelinids. We investigated an undescribed species of Coccophagus (Hymenoptera: Aphelinidae), an Australian parasitoid that attacks the introduced lantana mealy bug, Phenacoccus parvus Morrison (Homoptera: Pseudococcidae), in Queensland. A year-long field survey regularly returned large numbers of female Coccophagus spec. near gurneyi individuals from P. parvus (total n = 4212), but only few males (n = 11). Males emerged from samples only when the encyrtid parasitoid Anagyrus diversicornis (Howard) (Hymenoptera: Encyrtidae) was present in samples in relatively high numbers. Laboratory oviposition tests confirmed that A. diversicornis is a male host and showed that males do not develop at the expense of conspecific females. Other studies show that males are attracted in numbers to virgin females held in cages above mealy bug-infested Lantana montevidensis (Spreng.) Briq. (Verbenaceae) in the field, demonstrating that they are common in the population as a whole. This confirms that the males need hosts other than conspecific females and that their usual hosts are present outside of the lantana/P. parvus system. The implications of these results for developing a realistic classification of heteronomous host relationships are discussed.

A calreticulin-like protein from endoparasitoid venom fluid is involved in host hemocyte inactivation

During oviposition, most endoparasitoid wasps inject maternal factors into their hosts to interfere with host immune reactions and ensure successful development of their progeny. Since encapsulation is a major cellular defensive response of insects against intruding parasites, parasitoids have developed numerous mechanisms to suppress the host encapsulation capability by interfering with every step in the process, including recognition, adherence and spreading. In previous studies, components of Cotesia rubecula venom were shown to inhibit melanization of host hemolymph by interfering with the prophenoloxidase activation cascade and facilitate expression of polydnavirus genes. Here we report the isolation and characterization of another venom protein with similarity to calreticulin. Results indicate that C rubecula calreticulin (CrCRT) inhibits hemocyte spreading behavior, thus preventing encapsulation of the developing parasitoid. It is possible that the protein might function as an antagonist competing for binding sites with the host hemocyte calreticulin, which mediates early-encapsulation reactions. (c) 2005 Elsevier Ltd. All rights reserved.

Spring Phenology of Butterflies : The role of seasonal variation in life-cycle regulation

Animals and plants in temperate regions must adapt their life cycle to pronounced seasonal variation. The research effort that has gone into studying these cyclical life history events, or phenological traits, has increased greatly in recent decades. As phenological traits are often correlated to temperature, they are relevant to study in terms of understanding the effect of short term environmental variation as well as long term climate change. Because of this, changes in phenology are the most obvious and among the most commonly reported responses to climate change. Moreover, phenological traits are important for fitness as they determine the biotic and abiotic environment an individual encounters. Fine-tuning of phenology allows for synchronisation at a local scale to mates, food resources and appropriate weather conditions. On a between-population scale, variation in phenology may reflect regional variation in climate. Such differences can not only give insights to life cycle adaptation, but also to how populations may respond to environmental change through time. This applies both on an ecological scale through phenotypic plasticity as well as an evolutionary scale through genetic adaptation. In this thesis I have used statistical and experimental methods to investigate both the larger geographical patterns as well as mechanisms of fine-tuning of phenology of several butterfly species. The main focus, however, is on the orange tip butterfly, Anthocharis cardamines, in Sweden and the United Kingdom. I show a contrasting effect of spring temperature and winter condition on spring phenology for three out of the five studied butterfly species. For A. cardamines there are population differences in traits responding to these environmental factors between and within Sweden and the UK that suggest adaptation to local environmental conditions. All populations show a strong negative plastic relationship between spring temperature and spring phenology, while the opposite is true for winter cold duration. Spring phenology is shifted earlier with increasing cold duration. The environmental variables show correlations, for example, during a warm year a short winter delays phenology while a warm spring speeds phenology up. Correlations between the environmental variables also occur through space, as the locations that have long winters also have cold springs. The combined effects of these two environmental variables cause a complex geographical pattern of phenology across the UK and Sweden. When predicting phenology with future climate change or interpreting larger geographical patterns one must therefore have a good enough understanding of how the phenology is controlled and take the relevant environmental factors in to account. In terms of the effect of phenological change, it should be discussed with regards to change in life cycle timing among interacting species. For example, the phenology of the host plants is important for A. cardamines fitness, and it is also the main determining factor for oviposition. In summary, this thesis shows that the broad geographical pattern of phenology of the butterflies is formed by counteracting environmental variables, but that there also are significant population differences that enable fine-tuning of phenology according to the seasonal progression and variation at the local scale.

Temperature and the synchrony of plant-insect interactions

Increasing temperatures resulting from climate change have within recent years been shown to advance phenological events in a large number of species worldwide. Species can differ in their response to increasing temperatures, and understanding the mechanisms that determine the response is therefore of great importance in order to understand and predict how a warming climate can influence both individual species, but also their interactions with each other and the environment. Understanding the mechanisms behind responses to increasing temperatures are however largely unexplored. The selected study system consisting of host plant species of the Brassicaceae family and their herbivore Anthocharis cardamines, is assumed to be especially vulnerable to climatic variations. Through the use of this study system, the aim of this thesis is to study differences in the effect of temperature on development to start of flowering within host plant species from different latitudinal regions (study I), and among host plant species (study II). We also investigate whether different developmental phases leading up to flowering differ in sensitivity to temperature (study II), and if small-scale climatic variation in spring temperature influence flowering phenology and interactions with A. cardamines (study III). Finally, we investigate if differences in the timing of A. cardamines relative to its host plants influence host species use and the selection of host individuals differing in phenology within populations (study IV). Our results showed that thermal reaction norms differ among regions along a latitudinal gradient, with the host plant species showing a mixture of co-, counter- and mixed gradient patterns (study I). We also showed that observed differences in the host plant species order of flowering among regions and years might be caused by both differences in the distribution of warm days during development and differences in the sensitivity to temperature in different phases of development (study II). In addition, we showed that small-scale variations in temperature led to variation in flowering phenology among and within populations of C. pratensis, impacting the interactions with the butterfly herbivore A. cardamines. Another result was that the less the mean plant development stage of a given plant species in the field deviated from the stage preferred by the butterfly for oviposition, the more used was the species as a host by the butterfly (study IV). Finally, we showed that the later seasonal appearance of the butterflies relative to their host plants, the higher butterfly preference for host plant individuals with a later phenology, corresponding to a preference for host plants in earlier development stages (study IV). For our study system, this thesis suggest that climate change will lead to changes in the interactions between host plants and herbivore, but that differences in phenology among host plants combined with changes in host species use of the herbivore might buffer the herbivore against negative effects of climate change. Our work highlights the need to understand the mechanisms behind differences in the responses of developmental rates to temperature between interacting species, as well as the need to account for differences in temperature response for interacting organisms from different latitudinal origins and during different developmental phases in order to understand and predict the consequences of climate change. 

Characteristics of the biological cycle of lutzomyia evandroi Costa Lima & Antunes, 1936 (diptera: psychodidae) under experimental conditions

XIMENES, Maria de Fátima Freire de Melo; MACIEL, Janaína Cunha; JERONIMO, Selma Maria Bezerra. Characteristics of the Biological Cycle of Lutzomyia evandroi Costa Lima & Antunes, 1936 (diptera: psychodidae) under experimental conditions. Memorias do Instituto Oswaldo Cruz, Rio de Janeiro, v.96, n.6, p.883-886, ago. 2001. Disponivel em: Acesso em: 4 out. 2010.

Characteristics of the biological cycle of lutzomyia evandroi Costa Lima & Antunes, 1936 (diptera: psychodidae) under experimental conditions

XIMENES, Maria de Fátima Freire de Melo; MACIEL, Janaína Cunha; JERONIMO, Selma Maria Bezerra. Characteristics of the Biological Cycle of Lutzomyia evandroi Costa Lima & Antunes, 1936 (diptera: psychodidae) under experimental conditions. Memorias do Instituto Oswaldo Cruz, Rio de Janeiro, v.96, n.6, p.883-886, ago. 2001. Disponivel em: Acesso em: 4 out. 2010.

Plasticity in Insect Olfaction: To Smell or Not to Smell?

International audience

Preferência alimentar e identificação das principais fontes de repasto sanguíneo de fêmeas Lutzomyia (Diptera: Psychodidae) em áreas endêmicas para leishmaniose visceral na grande Natal

Leishmaniasis are endemic diseases wild spread in the New and Old World, caused by the flagelated protozoan Leishmania. In the New World, the distribution of different forms of leishmaniasis is mostly in tropical regions. In the State of Rio Grande do Norte, Northeast Brazil, 85% of the captured sand flies fauna is Lutzomyia longipalpis. The distribution of the sand fly vector in the state overlaps with the disease distribution, where the presence of sand flies is associated with presence of animals shelters. The aim of this study was to analyse the blood meal preference of sand flies vector from the genus Lutzomyia spp. in laboratory conditions, to verify the vector life cicle at different temperatures sets and to identify the main blood meal source in endemic areas for visceral leishmaniasis (VL) at peri-urban regions of Natal. Sand flies samples were collected from the municipalities of São Gonçalo do Amarante and Nísia Floresta where female sand flies were grouped for the colony maintenance in the laboratory and for the analysis of the preferred source of sand fly blood meal in natural environment. The prevalence of blood meal preference and oviposition for the females sand flies was 97% for Cavia porcellus with oviposition of 19 eggs/female; 97% for Eqqus caballus with 19 eggs/female; 98% for human blood with 14 eggs/female; 71.3% for Didelphis albiventris with 8.4 eggs/female; 73% for Gallus gallus with 14 eggs/female; 86% for Canis familiaris with 10.3 eggs/female; 81.4% for Galea spixii with 26 eggs/female; 36% for Callithrix jachus with 15 eggs/female; 42.8% for Monodelphis domestica with 0% of oviposition. Female sand flies did not take a blood meal from Felis catus. Sand flies life cycle ranged from 32-40 days, with 21-50 oviposition rates approximately. This study also showed that at 32°C the life cycle had 31 days, at 28° C it had 50 days and at 22°C it increased to 79 days. Adjusting the temperature to 35°C the eggs did not hatch, thus blocking the life cycle. A total of 1540 sand flies were captured, among them, 1.310 were male and 230 were female. Whereas 86% of the sand flies captured were Lu. longipalpis as compared to 10.5% for Lu. evandroi and, 3.2% for L. lenti and 0.3% for Lu whitmani. The ratio between female and male sandfly was approximately 6 males to 1 female. In Nísia Floresta, 50.7% of the collected females took their blood meal from armadillo, 12.8% from human. Among the female sand flies captured in São Gonçalo do Amarante, 80 of them were tested for the Leishmania KDNA infectivity where 5% of them were infected with Leishmania chagasi. Female Lutzomyia spp. showed to have an opportunistic blood meal characteristic. The behavioral parameters seem to have a higher influence in the oviposition when compared to the level of total proteins detected in the host s bloodstream. A higher Lu. longipalpis life cycle viability was observed at 28°C. The increase of temperature dropped the life cycle time, which means that the life cycle is modified by temperature range, source of blood meal and humidity. Lu longipalpis was the most specie found in the inner and peridomiciliar environment. In Nísia Floresta, armadillos were the main source of blood meal for Lutzomyia spp. At São Gonçalo do Amarante, humans were the main source of blood meal due to CDC nets placed inside their houses

Estudos bioecológicos da mosca mineira Liriomyza (diptera: agromyzidae) e dos seus parasitóides, em culturas protegidas, no Algarve

Tese de dout. em Ciências Agrárias, especialidade Protecção de Plantas, Faculdade de Engenharia e Recursos Naturais, Univ. do Algarve, 2001

Aspectos da biologia reprodutiva de Eretmochelys imbricata (testudines, cheloniidae) no litoral sul do Rio Grande do Norte, Brasil

Female hawksbill turtles (Eretmochelys imbricata) nesting along the southeastcoastline of Rio Grande do Norte State, Brazil (6º13'40"S, 35º03'05"W) were captured and weighed during the four months from January to April 2007, in the course of the annual egglaying season, which extended from 06 rd November 2006 to 30 rd May 2007. In all, 99 weight measurements were performed. On first contact the females exhibited an average post-oviposition weight of 79.1 kg (range 56.2-98.9 kg, SD = 10.9 kg, n = 44 females). Those individuals which were subsequently recaptured showed a mean weight loss of 1.7 kg (range 0.7-4.5 kg, SD = 1.0 kg, n = 39 sets of measurements on 20 females) in the interval between two consecutive post-ovipositions, separated by a maximum time interval of 17 days. In the cases where the female aborted the nesting process, the pre-oviposition weight was measured. The clutch weight, that is to say, the weight loss between consecutive pre-oviposition and post-oviposition measurements (separated by a maximum time interval of 3 days), was found to be 5.2 kg (range 4.3-6.0 kg, SD = 0.9 kg, n = 6 sets of measurements). This value is significantly higher (t-test, p<0.001) than the loss between two consecutive post-oviposition measurements with the same female. The mean recovery in body weight, that is to say, the average gain in weight between successive post-oviposition and pre-oviposition captures of the same individual (separated by a time interval of 12 to 17 days), was found to be 3.0 kg (range 1.9-4.3 kg, SD = 1.0 kg, n = 4 sets of measurements) Although the small sample size makes it unwise to generalise, the recovery in body weight was found to be always significantly lower (t-test, p<0.005) than the clutch weight. This fact is in agreement with the observed weight loss tendency throughout the breeding season for this species. Considering the clutch weight and the internidal recovery in body weight we found that the total weight loss of the adult hawksbill females after three to five nesting events varied from 10.4% (range 8.7-11.9%, SD = 1.6%, n = 3) to 14.1% (range 11.8-15.4%, SD = 1.3%, n = 6) in relation to their initial pre-oviposition weight. If there were no body weight recovery during the internesting interval we estimate that a female that nests three to five times in the course of the season would lose from 19% to 31% of its initial weight. We emphasise that our clutch weight estimate was performed by weighing the females and not by multiplying the number of eggs in the nest by their average unit weight. In this way, our measurements take into account the loss of liquid during the oviposition. Despite the unequivocal evidence of body weight recovery during the internidal interval, it is not clear if the cause of this process is rehydration or feeding

Estratégias de acasalamento e qualidade do espermatóforo em heliconius (Lepidoptera, Nymphalidae)

Butterflies are insects known, in a variety of environments and for easy visual identification. The adult form may be frequently found in flowers looking for nectar. However, for many species of Heliconius (Lepidoptera, Nymphalidae) to visit the flower also represents the collecting of pollen, an important source of protein for adults. The protein obtained from the pollen allows the maintenance of physiological processes that increase the performance of the individual, promoting greater longevity and egg production. For males, proteins can also be part in your investment in reproductive success and fitness of offspring through a nutritional contribution that is transferred to the female in the act of mating as a nuptial present. It is known that this protein contains essential to the performance of the female oviposition, however the proportion of content and specific importance to the monogamous and polygamous species is not known yet. Whereas the species studied in this work have different patterns of mating in the strategy was to verify a significant difference in the quality of the spermatophore, and H. erato and H. melpomene, on the amount of protein present in this structure, indicating a difference in investment between the male reproductive strategies