RESUMO
The existence of a pheromone emitted during copulation has been reported for Rhodnius prolixus (Hemiptera: Reduviidae) Stål. Adults possess one pair of metasternal glands (MGs) from which female R. prolixus release volatiles mainly at night. We investigated whether these volatiles emitted by adult R. prolixus can modulate sexual-related behaviours of opposite and/or same sex individuals. We first used a shelter bioassay to test if adult activity patterns can be affected by chemical signals emitted by opposite sex conspecifics. We observed that males left the shelter more frequently in the presence of females, showing higher activity and an increase of intrasexual copulation attempts. Females showed no shelter-related activation in the presence of male odours. Second, we used a locomotion compensator device to investigate whether females or males show oriented responses to odours emitted by adults. We found that males oriented towards air currents carrying female odours but females did not orient towards odours emitted by adults. Finally, we observed that males oriented towards the female MG compounds. Thus, a volatile chemical signal emitted by females from their MGs promoted the activation of sheltered males and modulated orientation to air currents.
Assuntos
Feromônios/metabolismo , Comportamento Sexual Animal/fisiologia , Triatominae/fisiologia , Movimentos do Ar , Animais , Feminino , Masculino , Atividade Motora/fisiologia , Orientação/fisiologiaRESUMO
We investigated whether metasternal gland (MG) products mediate male aggregation during mating in Rhodnius prolixus (Heteroptera: Reduviidae) Stål, 1859, through selective occlusion of female MGs. Pairs of insects presenting intact MGs mated and other males aggregated around them confirming conclusions from previous studies. However, when female MGs were occluded, males did not aggregate. Conversely, the occlusion of male MGs did not affect aggregation of males. The present experiments demonstrated that the products emitted by the MGs of a mating R. prolixus female induce other males to aggregate around the mating pair. Aggregation behaviour of males probably results from the eventual release of volatiles from the female's MGs. We reinforce the hypothesis suggesting that the compounds produced by the MGs of R. prolixus act as sexual communication signals for this species.
Assuntos
Odorantes , Rhodnius/fisiologia , Atrativos Sexuais/fisiologia , Animais , Feminino , Masculino , Comportamento Sexual Animal , Comportamento SocialRESUMO
The present work tested whether Triatoma pseudomaculata Corrêa & Espínola shows behavioral traits indicating that it is capable of feeding on arthropods. We consistently observed nymphs extending their proboscis in the direction of cockroaches and attempting to bite. Insects presented a preference for biting specific cockroach body parts. Our results suggest that arthropod hemolymph represents an alternative source of food that increases the survival of T. pseudomaculata individuals undergoing long starvation.
Assuntos
Periplaneta/parasitologia , Triatoma/fisiologia , Animais , Comportamento AlimentarRESUMO
Triatoma brasiliensis is considered the main vector of Chagas disease in the semiarid zones of North-eastern Brazil. In this work, we describe the spatial pattern of defecation in T. brasiliensis and the spatial relationship of faeces with the shelters of these bugs. Afterwards, we analyse the attraction response of T. brasiliensis larvae to potential odour cues present in their dry faeces, to substances present in their cuticule (footprints) and to the dry faeces of Triatoma pseudomaculata. We show that faecal spots are deposited in a larger density inside the shelter than in the remaining area available for the bugs. T. brasiliensis larvae were significantly attracted towards their own faeces, and also to those of T. pseudomaculata. In contrast to other triatomine species, footprints did not promote attraction in T. brasiliensis. The potential use of communication signals of T. brasiliensis as tools for helping control this species is discussed.
Assuntos
Comunicação Animal , Insetos Vetores/fisiologia , Triatoma/fisiologia , Animais , Brasil , Doença de Chagas/transmissão , Defecação , Fezes/química , Insetos Vetores/crescimento & desenvolvimento , Larva/fisiologia , Triatoma/crescimento & desenvolvimentoRESUMO
The thermopreference of resting P. megistus (Burmeister, 1834) adults was studied in a temperature gradient. We also determined the thermopreference for oviposition and ecdysis. Thermopreference of resting individuals depended on the feeding state of the insects. Results demonstrated an initial resting preference of approximately 290 degrees C, which gradually changed to 26-27 degrees C with increasing starvation. A daily variation in thermopreference was also observed with this species. The insects showed a daily maximum preference at the beginning of the dark phase, and a minimum preference during the first half of the light phase. Ecdysis took place all along the gradient, but exhibited a maximum frequency at 30 degrees C. Most eggs were found between 25 and 29 degrees C. Results are discussed in relation to the ecology of P. megistus as compared with other related species, and the existence of mechanisms of behavioral thermoregulation in the group.
Assuntos
Comportamento Animal , Insetos Vetores/fisiologia , Panstrongylus/fisiologia , Animais , Doença de Chagas , Feminino , Oviposição , TemperaturaRESUMO
We tested the aggregation response to inter and intraspecific chemical signals in Panstrongylus megistus and Triatoma infestans. As previously described for T. infestans, larvae of P. megistus significantly aggregated on papers impregnated with their own excrement and on papers marked with cuticular substances deposited on surfaces on which these insects had walked. T. infestans bugs also aggregated on papers impregnated by faeces or by cuticular substances of P. megistus, and P. megistus aggregated on papers contaminated by faeces or by cuticular substances of T. infestans. The response of P. megistus to its cuticular substances was significantly stronger than that to its faeces. The non-specificity of the two signals is discussed in the context of the ecological relationship between both species.
Assuntos
Panstrongylus/fisiologia , Triatoma/fisiologia , Animais , Comportamento Animal , Vetores de Doenças , Fezes , Larva/fisiologia , Especificidade da EspécieRESUMO
Vector-borne transmission of Chagas disease in Northeast Brazil is basically by Triatoma brasiliensis. It is thus crucial to determine this species' microclimatic preferences as limiting factors for its distribution and ability to infest domestic environments. We analyze the microclimatic properties of the shelters in which these insects are found in wild, domestic, and peridomiciliary environments in the State of Ceará, at Brazil. We measure temperature and relative humidity (RH) every 15 minutes for 3 days. Thermal variation was greatly dampened inside both domiciliary refuges and the more protected internal places in wild stony sites. For RH, we observed a similar dampening pattern, but mean RH was lower in both domiciliary refuges and wild ones inside stony sites as compared to reference levels in the surrounding environment. The results are discussed with regard to this species' microclimatic preferences in the laboratory and its potential as determinants of its geographical distribution.
Assuntos
Insetos Vetores/fisiologia , Microclima , Triatoma/fisiologia , Animais , Doença de Chagas/prevenção & controle , Reservatórios de Doenças , Ecologia , Umidade , TemperaturaRESUMO
The effectiveness of a trap for triatomines baited with yeast cultures has been previously demonstrated for Triatoma infestans in laboratory assays. We report here results from laboratory assays testing yeast traps for Triatoma sordida, Triatoma brasiliensis, Triatoma pseudomaculata, and Panstrongylus megistus. All assays were conducted in an open experimental arena 100 cm x 100 cm, with two traps placed at opposite sides of the arena. One of the traps contained a yeast culture, and the other trap contained a saccharose solution as a control. Two series of experiments were done, one without a refuge for the insects and one with a refuge. The results obtained clearly demonstrated that the yeast-baited traps were effective in the laboratory in capturing both T. sordida and P. megistus. For T. sordida, yeast-baited traps captured significantly more bugs than did the control traps (t test P value = 0.03). For P. megistus, when a refuge was provided during the assay, yeast-baited traps also captured significantly more bugs than did the control traps (t test P value = 0.006). In the experiments with T. brasiliensis and T. pseudomaculata, both traps captured some insects, but the yeast traps captured many fewer bugs than was true with the T. sordida and P. megistus bugs. These results indicate that, in the laboratory, yeast traps can capture considerable numbers of T. sordida and P. megistus in one night. We discuss the potential use of yeast traps for detecting and capturing both triatomine species.
Assuntos
Doença de Chagas/prevenção & controle , Controle de Insetos/métodos , Insetos Vetores , Panstrongylus , Triatoma , Animais , Laboratórios , Fatores de Tempo , LevedurasRESUMO
The preference of Triatoma infestans for shelters at different temperatures or relative humidities (RH) was tested in laboratory assays. The insects preferred refuges at a temperature of 34 degrees C rather than 26 degrees C, and chose to stay in refuges with an RH of 20% rather than 80%. Temperature and RH records made inside and outside experimental chicken-houses under natural climatic conditions showed that such habitats tend to maintain an inner climate favourable to T. infestans. Typical refuges in adobe walls showed strongly damped fluctuations in minimum and maximum temperatures, and delayed changes in these parameters when compared with an external reference. Similarly, the jarilla (Larrea sp.), a plant used for constructing roofing, damps fluctuations in minimum and maximum RH and delays these RH fluctuations when compared to an external reference. We discuss possible effects of environmental factors on the distribution of insects in human dwellings, and analyse the environmental characteristics of normally available refuges in materials used for house building in endemic zones.
Assuntos
Doença de Chagas/transmissão , Umidade , Insetos Vetores/fisiologia , Triatoma/fisiologia , Animais , TemperaturaRESUMO
Responses to air currents carrying volatiles from yeast cultures were measured by means of electroantennograms (EAGs) in the haematophagous bug Rhodnius prolixus and we tested yeast-baited traps in the laboratory. The volatiles liberated by yeast cultures generated a clear electrophysiological response, much higher than that obtained during stimulation with clean air. The addition of yeast cultures to the traps dramatically increased overnight capture. A modification performed on the traps was effective for this species, as the bugs were immobilised once they fell into the device. Our results demonstrate that yeast culture volatiles are attractive for R. prolixus. The results obtained by means of electroantennogram techniques represent the first electrophysiological evidence of the perception of yeast volatiles by the antennae of a triatomine bug. We discuss the relevance of our results in view of currently used sampling techniques and control strategies.