Allatotropin modulates myostimulatory and cardioacceleratory activities in <i>Rhodnius prolixus</i> (Stal)

Haematophagous insects can ingest large quantities of blood in a single meal and eliminate high volumes of urine in the next few hours. This rise in diuresis is possible because the excretory activity of the Malpighian tubules is facilitated by an increase in haemolymph circulation as a result of intensification of aorta contractions combined with an increase of the anterior midgut peristaltic waves. It has been previously described that haemolymph circulation during post-prandial diuresis is stimulated by the synergistic activity of allatotropin (AT) and serotonin in the kissing bug Triatoma infestans; resulting in an increase in aorta contractions. In the same species, AT stimulates anterior midgut and rectum muscle contractions to mix urine and feces and facilitate the voiding of the rectum. Furthermore, levels of AT in midgut and Malpighian tubules increased in the afternoon when insects are getting ready for nocturnal feeding. In the present study we describe the synergistic effect of AT and serotonin increasing the frequency of contractions of the aorta in Rhodnius prolixus. The basal frequency of contractions of the aorta in the afternoon is higher that the observed during the morning, suggesting the existence of a daily rhythmic activity. The AT receptor is expressed in the rectum, midgut and dorsal vessel, three critical organs involved in post-randial diuresis. All together these findings provide evidence that AT plays a role as a myoregulatory and cardioacceleratory peptide in R. prolixus.Facultad de Ciencias Naturales y Muse

Allatotropin Modulates Myostimulatory and Cardioacceleratory Activities in Rhodnius prolixus (Stal)

Fil: Villalobos-Sambucaro, María José. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra Histología y Embriología Animal; ArgentinaFil: Lorenzo-Figueiras, Alicia Nieves. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Riccillo, Fernando Luis. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra Histología y Embriología Animal; ArgentinaFil: Diambra, Luis Anibal. Universidad Nacional de La Plata. Centro Regional de Estudios Genómicos; ArgentinaFil: Noriega, Fernando Gabriel. Florida International University. Department of Biological Sciences; USAFil: Ronderos, Jorge Rafael. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra Histología y Embriología Animal; Argentin

Allatotropin modulates myostimulatory and cardioacceleratory activities in <i>Rhodnius prolixus</i> (Stal)

Haematophagous insects can ingest large quantities of blood in a single meal and eliminate high volumes of urine in the next few hours. This rise in diuresis is possible because the excretory activity of the Malpighian tubules is facilitated by an increase in haemolymph circulation as a result of intensification of aorta contractions combined with an increase of the anterior midgut peristaltic waves. It has been previously described that haemolymph circulation during post-prandial diuresis is stimulated by the synergistic activity of allatotropin (AT) and serotonin in the kissing bug Triatoma infestans; resulting in an increase in aorta contractions. In the same species, AT stimulates anterior midgut and rectum muscle contractions to mix urine and feces and facilitate the voiding of the rectum. Furthermore, levels of AT in midgut and Malpighian tubules increased in the afternoon when insects are getting ready for nocturnal feeding. In the present study we describe the synergistic effect of AT and serotonin increasing the frequency of contractions of the aorta in Rhodnius prolixus. The basal frequency of contractions of the aorta in the afternoon is higher that the observed during the morning, suggesting the existence of a daily rhythmic activity. The AT receptor is expressed in the rectum, midgut and dorsal vessel, three critical organs involved in post-randial diuresis. All together these findings provide evidence that AT plays a role as a myoregulatory and cardioacceleratory peptide in R. prolixus.Facultad de Ciencias Naturales y Muse

Allatotropin modulates myostimulatory and cardioacceleratory activities in <i>Rhodnius prolixus</i> (Stal)

Haematophagous insects can ingest large quantities of blood in a single meal and eliminate high volumes of urine in the next few hours. This rise in diuresis is possible because the excretory activity of the Malpighian tubules is facilitated by an increase in haemolymph circulation as a result of intensification of aorta contractions combined with an increase of the anterior midgut peristaltic waves. It has been previously described that haemolymph circulation during post-prandial diuresis is stimulated by the synergistic activity of allatotropin (AT) and serotonin in the kissing bug Triatoma infestans; resulting in an increase in aorta contractions. In the same species, AT stimulates anterior midgut and rectum muscle contractions to mix urine and feces and facilitate the voiding of the rectum. Furthermore, levels of AT in midgut and Malpighian tubules increased in the afternoon when insects are getting ready for nocturnal feeding. In the present study we describe the synergistic effect of AT and serotonin increasing the frequency of contractions of the aorta in Rhodnius prolixus. The basal frequency of contractions of the aorta in the afternoon is higher that the observed during the morning, suggesting the existence of a daily rhythmic activity. The AT receptor is expressed in the rectum, midgut and dorsal vessel, three critical organs involved in post-randial diuresis. All together these findings provide evidence that AT plays a role as a myoregulatory and cardioacceleratory peptide in R. prolixus.Facultad de Ciencias Naturales y Muse

Aggregation behaviour and Intra- and Interspecific communication in triatominae

Los triatominos activos durante la noche, permanecen durante el día agrupados en sitios protegidos. El comportamiento de agregación está mediado por tigmotaxis y por señales químicas. Experimentos utilizando arenas y olfatómetros muestran que Triafoma infestans es atraída a papeles impregnados con sus heces secas. La respuesta de agregación depende del tiempo transcurrido luego de la ingesta: insectos recién alimentados no se agrupan, cambiando su respuesta cambia al cabo de 8-10 horas. Los compuestos activos pudieron ser extraídos de las deyecciones con solventes polares. Los mismos podrían ser productos finales de la digestión de la sangre o secreciones adicionadas al contenido del recto antes de la deposición. El significado biológico de está señal ha sido relacionado con la orientación hacia los refugios. Una kairomona de agregación está presente en las heces de T. infestans, T. sordida, T. guasayana y Rhodnius prolixus. Los excrementos de T. infesfans promueven la agregación en T. sordida y T. guasayana, pero no en R. prolixus. Las heces de estas tres especies inducen la agregación en T. infesfans. Otro factor de agregación, extraible por solventes no-polares, está presente en la cutícula de las vinchucas.. Esta señal actúa a través de un mecanismo de quimiorrecepción de contacto.Night-active triatomines spend daytime hours assembled in protected places. The aggregation behaviour is mediated by thigmotaxis and by chemical cues. Experiments using arenas and wind-tunnel olfactometers show that Triatoma infesfans are attracted to papers impregnated with their own dry faeces. The assembling response depends on the time elapsed after feeding: recently fed animals are not attracted, but a switch in the response takes place after 8-10 hours. The active compounds can be extracted from faeces by polar solvents. It may be a product of the final breakdown of the blood meal or could be a secretion added to the contents of the rectum prior to defecation. It has been proposed that the faecal signal help the insects to orientate towards refuges. An aggregation kairomone is present in the faeces of T. infesfans, T. soradida, T. guasayana and Rhodnius prolixus. We found that excrements of T. infesfans elicit assembling in T. sordida and T. guasayana, but not in R. prolixus. The excrement of the last three named species induce aggregation in T. infestans. A novel aggregation factor is described, which can be extracted from the cuticle of the insects by non-polar solvents and acts through contact chemoreception.Fil:Lorenzo Figueiras, Alicia Nieves. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Aggregation behaviour and interspecific responses in three species of Triatominae

The response to intra- and interspecific assembling signals was tested in three species of Chagas' disease vectors. As previously described for Triatoma infestans, larvae of both species, T. sordida and T. guasayana, aggregated on papers impregnated with their own excrement. Moreover, bugs belonging to each of the three species also aggregated on papers contaminated with faeces from the other two, with the only exception of the larvae of T. guasayana, which did not assemble on faeces of T. sordida. In all cases, the response to interspecific excrement was as strong as that to the intraspecific one. The non-specificity of the signal is discussed in the context of the ecological association of the three species and their role as vectors of Chagas' disease

Aggregation behaviour and interspecific responses in Rhodnius prolixus Stål

The response to intra- and interspecific faecal assembling signals was tested in Rhodnius prolixus   . Papers impregnated with excrement of R. prolixus induced the aggregation of larvae of this species, but also of those of Triatoma infestans   . However, faeces belonging to T. infestans were not able to assemble larvae of R. prolixus . On the other hand, there was no response of R. prolixus to putative chemical factors from their cuticle (footprints), in contrast to T. infestans . Results are discussed as related to the ecology of both species

Temporal change of the aggregation response in Triatoma infestans

Adults and larvae of Triatoma infestans spend daylight hours assembled in shaded places. An assembling factor has been demonstrated in the excrement of this species. We analysed different aspects of the dynamics of the response of bugs. Recently fed insects do not aggregate around faeces. They start to show a significant assembling response from the 8th hour after feeding onwards. Just deposited faeces do not evoke assembling, but a significant rejection instead. This reaction switches 3 h after deposition, when the faeces become attractive to the insects. The attractiveness of faeces persists for about 10 days and can be recovered after this time by rehydration. These findings are discussed in relation to the biological role of faeces and the dynamics of the use of refuges by T. infestans

Spatio-temporal analysis of the role of faecal depositions in aggregation behaviour of the triatomine Rhodnius prolixus

Several triatomine species aggregate over conspecific faeces. In some domestic species, this behaviour might help individuals to find their refuges because faeces are usually deposited around such places. In the present study, the defaecation behaviour of the triatomine bug Rhodnius prolixus Stål (Heteroptera: Reduviidae) is described in detail, including the temporal pattern of aggregation of nymphs with different nutritional status to faeces of different post-deposition times. First, using an experimental arena, the spatial distribution of faecal deposition spots released by nymphs, in relation to the position of a refuge, is recorded. The results show that a high density of faeces is deposited inside the refuge, and few and distant spots, in relation to the position of the refuge, are dropped outside. Second, whether the aggregation behaviour of nymphs is altered by the time elapsed from deposition of the faeces, and by the nutritional status of the insects, is determined. The post-deposition time of the faeces strongly modulates the aggregation response of the insects. Differences in aggregation between fed and unfed insects are only marginally significant; however, different temporal windows of aggregation according to the post-deposition times of the faeces are demonstrated between bugs of different nutritional status. The results are discussed with respect to the relevance of the aggregation signal in relation to the characteristics of the natural refuges used by R. prolixus.Fil: Falvo, Marianel L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Lorenzo Figueiras, Alicia Nieves. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Manrique, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentin

Experience-dependent modulation of the attraction to faeces in the kissing bug Triatoma infestans

Triatoma infestans is the main vector of the Chagas disease in Latin America. These nocturnal bugs spend most of the daylight hours aggregated with conspecifics inside crevices in roofs and walls. Around the entrances of the shelters T. infestans deposits faeces that contain chemical cues that attract conspecifics. In this work we investigated whether attraction to faeces can be modulated by experience in this insect species. First, we analyzed if the attraction of nymphs to faeces is innate or acquired through previous sensory experiences. Results show that after hatching, 1st instar nymphs are attracted to faeces even if they had never been in contact with them before, thus indicating that this attraction is innate. Second, we studied if attraction to faeces can be influenced by the presence of con-specifics. No differences were found in the attraction to faeces of nymphs released alone or in groups, suggesting that attraction to faeces is independent of the presence of other individuals. Third, we examined if the innate response to faeces of nymphs can be modulated by experience. After pre-exposing nymphs to faeces during 24 h, insects were no longer attracted to faeces. Finally, by pairing the presence of faeces with an aversive mechanical disturbance, nymphs switched from attraction to avoidance of faeces. These results show that although faeces attraction has a strong innate component, it can be modulated by experience. The learning and memory capacities of triatomines have been studied only recently, and our work is the first report on the effects of experience in the aggregation context.Fil: Mengoni, Sofia Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Fisiología de Insectos; ArgentinaFil: Lorenzo Figueiras, Alicia Nieves. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Fisiología de Insectos; ArgentinaFil: Minoli, Sebastian Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Fisiología de Insectos; Argentin