Behavioral strategies of phorid parasitoids and responses of their hosts, the leaf-cutting ants

Host-searching and oviposition behaviors of parasitoids, and defensive responses of the hosts, are fundamental in shaping the ecology of host-parasitoid interactions. In order to uncover key behavioral features for the little known interactions between phorid parasitoids (Diptera: Phoridae) and their leaf-cutting ant hosts (Formicidae: Attini), host-related behavioral strategies (i.e., host searching and oviposition) for 13 phorid species, and host defensive responses (i.e., hitchhikers and particular body postures) for 11 ant species, were studied. Data was collected at 14 localities, one of them characterized by its high species richness for this host-parasitoid system. Phorid species showed both great variation and specificity in attacking behaviors. Some chose their hosts using either an ambush or an actively searching strategy, while some species attacked ants on different body parts, and specialized on ants performing different tasks, such as when ants were foraging, removing wastes to refuse piles, or repairing the nest. Combining all the behaviors recorded, most phorid species differed in performance in at least one, making it possible to recognize species in the field through their behavior. Phorid species that attacked hosts with greater activity levels showed overall higher attack rates, although there was no significant correlation between attack rates by most phorid species and ant activity outside the nest while parasitoids were attacking. The presence of phorids was a significant determinant for the presence of defensive behaviors by the ants. Although ant species varied in the incidence levels of these defensive behaviors, most ant species reacted against different phorids by utilizing similar behaviors, in contrast to what parasitoids do. General features of the observed phorid-ant interactions were parasitoid specialization and corresponding high interspecific variation in their behaviors, while their hosts showed generalized responses to attacks with high intraspecific variation. Behavioral patterns as well as specific features of these ant-parasitoid interactions are described, and their ecological importance discussed.Fil: Elizalde, Luciana. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Folgarait, Patricia Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; Argentin

Host diversity and environmental variables as determinants of the species richness of the parasitoids of leaf-cutting ants

Aim Because of the obligatory relationship between endoparasitoids and their hosts, we presume that hosts exert strong selection pressure on parasitoids. One prediction is a positive relationship between host diversity and parasitoid richness. This relationship could be the product of resource availability which could lead to more opportunities for speciation, or could represent shared responses to the environment by both groups.Location Argentina and Paraguay.Methods We sampled a 1800-km transect to test for a correlation between the richness of leaf-cutting ant hosts and their phorid parasitoids. Regression models were used to assess if host and environmental variables could explain phorid species richness at nest, hectare and locality spatial scales. We used canonical correspondence analysis (CCA) to explore if there were similar responses of phorid species to particular host and environmental variables at different spatial scales, and partial CCA to separate the relative importance of both groups of variables.Results Phorid richness was positively correlated with host richness. Host richness/abundance accounted for 20-53% of the variation in parasitoid richness at the hectare and locality scales of analysis, with most of the variation accounted for by ant abundance. We were not able to assess the prediction at the nest scale as only one phorid species was found at most nests. Climatic variables did not explain phorid species richness once host variables were in the models. Partial CCA showed that host-related variables accounted for most of the variance associated with phorid species ordination at the nest and hectare scales, but not at the largest grain, the locality, where climatic variables were more important. However, most phorid species did not show particular positions along the climatic gradient.Main conclusions The association between parasitoid richness and host richness and abundance, and the overall weak associations with environmental variables, suggest that these host variables are key factors influencing parasitoid speciation.Fil: Elizalde, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Folgarait, Patricia Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; Argentin

Las hormigas cortadoras de hojas y sus enemigos

En la estepa patagónica, las hormigas cortadoras son presa de depredadores muy diferentes. Si aprendemos de estas interacciones podremos controlar a las hormigas de forma más natural cuando nos perjudique

Parasitoids of Acromyrmex (Hymenoptera: Formicidae) Leaf-Cutting Ants in Continuous and Fragmented Atlantic Forest

Fragmentation of the habitat is a major threat to biodiversity in Atlantic forest. Parasitoids seem to be particularly susceptible to habitat fragmentation. This study evaluated whether habitat fragmentation affected the interactions between phorid parasitoids and their Acromyrmex leaf-cutting ant host. Host density, and parasitoid species richness, abundance and proportion of nests with phorids were compared for a fragmented landscape and a well-preserved continuous forest in the Atlantic forest in Rio de Janeiro. Five Acromyrmex species and seven species of phorid parasitoids were found, most of them attacking exclusively Acromyrmex niger (Smith). Host nest density was similar in continuous and fragmented forests, and host species density was higher in fragmented forest. Parasitoid species richness, abundance and proportion of ant nests with phorids were higher in the continuous forest. This work showed for the first time the negative effect that forest fragmentation has on parasitoid species of Acromyrmex ants, apparently due to phorid inability to reach fragments. However, even when phorid abundance was considerably reduced in forest fragments, phorids of some species were able to parasitize ants there. In addition, the quantitative interactions among Acromyrmex ants and their parasitoids in Atlantic forest are described for the first time

Una especie nueva de Anochetus (Hymenoptera: Formicidae: Ponerini) asociada a hormigas cortadoras de hojas de Argentina y Paraguay

A new species of the ant genus Anochetus is described from Argentina and Paraguay. Anochetus miserabilis Gonz\ue1lez-Campero & Elizalde sp. nov. is included within the "emarginatus" group, which is distributed in northern South America and the Antilles. With the inclusion of this new species, the distribution of the group is extended to southern South America. Observations of its biology and peculiar association with a leaf cutter ant species are given. In addition, illustrations and a key for the worker caste of the species of the genus present in Argentina and Paraguay are included.Se describe una nueva especie del g\ue9nero para la Argentina y Paraguay. Anochetus miserabilis Gonz\ue1lez-Campero & Elizalde sp. nov. se incluye dentro del grupo "emarginatus", el cual se distribuye en el norte de Sudam\ue9rica y las Antillas. Con la inclusi\uf3n de esta nueva especie, la distribuci\uf3n de "emarginatus" se extiende hasta el sur de Sudam\ue9rica. Se incluyen observaciones de su biolog\ueda y su curiosa asociaci\uf3n con hormigas cortadoras de hojas. Se presentan, adem\ue1s, ilustraciones y una clave para obreras de Anochetus de la Argentina y Paraguay

Molecular and biological characterization of hepatitis B virus subgenotype F1b clusters: Unraveling its role in hepatocarcinogenesis

Hepatitis B virus (HBV) subgenotype F1b infection has been associated with the early occurrence of hepatocellular carcinoma in chronically infected patients from Alaska and Peru. In Argentina, however, despite the high prevalence of subgenotype F1b infection, this relationship has not been described. To unravel the observed differences in the progression of the infection, an in-depth molecular and biological characterization of the subgenotype F1b was performed. Phylogenetic analysis of subgenotype F1b full-length genomes revealed the existence of two highly supported clusters. One of the clusters, designated as gtF1b Basal included sequences mostly from Alaska, Peru and Chile, while the other, called gtF1b Cosmopolitan, contained samples mainly from Argentina and Chile. The clusters were characterized by a differential signature pattern of eight nucleotides distributed throughout the genome. In vitro characterization of representative clones from each cluster revealed major differences in viral RNA levels, virion secretion, antigen expression levels, as well as in the localization of the antigens. Interestingly, a differential regulation in the expression of genes associated with tumorigenesis was also identified. In conclusion, this study provides new insights into the molecular and biological characteristics of the subgenotype F1b clusters and contributes to unravel the different clinical outcomes of subgenotype F1b chronic infections.Fil: Elizalde, Maria Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Mojsiejczuk, Laura Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; ArgentinaFil: Speroni, Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Bouzas, Belén. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Tadey, Luciana. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mammana, Lilia. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Campos, Rodolfo Hector. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Flichman, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; Argentin

“Hormiga Argentina” Linepithema humile

En Argentina existen mas de 600 especies de hormigas y solo una de ellas (Linepithema humile) es la que llamamos "hormiga argentina". Si bien su nombre nos remite a nuestro país, esta hormiga originaria de la cuenca del Paraná (sur de Brasil, noreste de Argentina, este de Paraguay y norte de Uruguay), es considerada invasora en otras regiones de Argentina (como por ejemplo Cuyo y Patagonia).Estación Experimental Agropecuaria BarilocheFil: Pirk, Gabriela Inés. Universidad Nacional del Comahue; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. INIBIOMA. Laboratorio de Investigaciones en Hormigas; ArgentinaFil: Werenkraut, Victoria. Universidad Nacional del Comahue; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Laboratorio ECOTONO; ArgentinaFil: Lescano, María Natalia. Universidad Nacional del Comahue; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. INIBIOMA. Laboratorio de Investigaciones en Hormigas; ArgentinaFil: Elizalde, Luciana. Universidad Nacional del Comahue; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. INIBIOMA. Laboratorio de Investigaciones en Hormigas; ArgentinaFil: Josens, Roxana Beatriz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Quantitative HBsAg an unreliable marker for diagnosis and disease progression in genotype F chronic HBeAg-negative infections

Quantitative hepatitis B surface antigen (qHBsAg) has been proposed as a biomarker to distinguish HBeAg-negative chronic infections (ENI) from HBeAg-negative chronic hepatitis (ENH), identify patients prone to achieving sustained HBsAg loss, and predict the risk of liver disease progression. There is evidence that qHBsAg varies among genotypes, however there is a paucity of data on genotype F. The aim of this study was to investigate the performance of qHBsAg in the diagnosis and evolution of genotype F chronic HBeAg-negative infections. HBV-DNA and HBsAg levels from 153 patients with ENI were correlated with the genotype. Liver disease progression was assessed by abdominal ultrasound and a transient elastography. The qHBsAg levels were significantly different among genotypes (p 3.0 log10 IU/ml, no cases of advanced liver disease were observed at the end of follow-up. This study provides new insights into the impact of HBV genotypes, in particular GTF, on serum HBsAg levels, emphasizing the need to implement a genotype-specific cut-off to achieve diagnostic certainty in the identification of ENI and the risk of liver disease progression. Regardless of HBV genotype, qHBsAg has been shown to be a powerful and reliable biomarker for predicting HBsAg loss.Fil: Fainboim, Hugo. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Di Benedetto, Nicolas. Hospital Arrecifes; ArgentinaFil: Paz, Silvia. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Mendizabal, Manuel. Universidad Austral; ArgentinaFil: Campuzano, Soledad. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Elizalde, Maria Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; ArgentinaFil: Tadey, Luciana. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Deluchi, Gabriel. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Bouzas, María Belén. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Mammana, Lilia. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Flichman, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas en Retrovirus y Sida. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas en Retrovirus y Sida; Argentin