ABSTRACT
Some ichneumonid wasps of the Polysphincta group of genera (Hymenoptera: Ichneumonidae: Pimplinae) induce behavioral modifications in their host spiders during a specific moment of their development, resulting in the construction of webs that differ in several aspects from those constructed by unparasitized individuals. In this study, we describe the parasitoid wasp Hymenoepimecis pinheirensis sp. n. (Ichneumonidae: Pimplinae) and present information on behavioral modifications in the orb-web structure of its host, the spider Leucauge volupis (Keyserling 1893). Previously, reported observation on this host/parasitoid interaction was restricted to one locality, and the wasp species was misidentified as Hymenoepimecis jordanensis Loffredo and Penteado-Dias 2009. Modified webs built by parasitized spiders lack adhesive spirals and have several radii that converge to the web hub. The cocoon built by the wasp larvae is attached to the web hub, suspended by horizontal radial lines, and surrounded by a tridimensional tangle positioned below the hub. This modified web structure is similar to the most frequent architecture of webs constructed by individuals of Leucauge mariana (Taczanowski 1881) parasitized by Hymenoepimecis tedfordi Gauld 1991. However, cocoon webs built by L. volupis parasitized by H. pinheirensis sp. n. differ from the cocoon webs described for the other Leucauge species parasitized by Hymenoepimecis wasps. This evidence suggests that the modified web pattern in Leucauge species is determined by specific responses of each spider species to the behavioral manipulation mechanism displayed by the wasps.
Subject(s)
Host-Parasite Interactions , Spiders , Wasps , Animals , Larva , Spiders/parasitology , Wasps/physiology , Species Specificity , Behavior, AnimalABSTRACT
This work aims to evaluate the use of parametric models instead of a nonparametric procedure to adjust survival curves related to different treatments, and to verify the equivalence among treatments by the multivariate method of cluster analysis. The dataset used to validate the method was obtained from a laboratory experiment with cutting ants. Eight colonies of cutting ants were used, each one receiving different treatments. The exponential, Weibull, log-normal, and logistic models were adjusted for each treatment, along with the usual Kaplan-Meier adjustment. The logistic model used was the best option for evaluating the survival of the ants. Therefore, this model was adjusted for each treatment. The estimates of the parameters of each adjusted model were clustered using Ward's method of multivariate technique of cluster analysis. Finally, heuristic techniques for choosing the number of clusters were applied in order to define the sets of equivalent treatments. For the dataset used, the proposed method was less laborious and as efficient as the logrank for the comparison of many survival curves.
Este trabalho tem como objetivo avaliar o uso de modelos paramétricos, ao invés do usual procedimento não paramétrico, no ajuste de curvas de sobrevivência em relação a diferentes tratamentos e ainda verificar a equivalência entre esses tratamentos através da técnica multivariada de análise de agrupamento. O conjunto de dados usado para validar o método foi obtido através de um experimento de laboratório com formigas cortadeiras. Oito colônias de formigas cortadeiras foram usadas, cada uma recebendo um tratamento diferente. Os modelos exponencial, Weibull, log-normal e logístico foram ajustados para cada tratamento além do usual ajustamento de Kaplan-Meier. O modelo logístico foi o mais aceitável para avaliar a sobrevivência das formigas. Portanto, esse modelo foi ajustado para cada tratamento. As estimativas dos parâmetros de cada modelo ajustado foram agrupadas utilizando o método de Ward da técnica multivariada de análise de agrupamento. Para o conjunto de dados usado, o método proposto foi menos trabalhoso e tão eficiente quanto o teste logrank para a comparação das várias curvas de sobrevivência.
