Abstract The source of Darwin’s illness has been a contentious issue in the literature for almost 70 years. Different causal factors have been invoked to account for his symptoms, including Chagas disease. The Chagas hypothesis is based upon Darwin’s diary, in which he narrates his experience with kissing bugs, the main vector of the protozoan Trypanosoma cruzi , the etiological agent of Chagas disease. In this contribution, we examine the consistency of the “Chagas disease hypothesis” in the light of current ecological and epidemiological knowledge of the disease in Chile. According to his diary and letters, during his overland trips, Darwin slept in rural houses and outdoors for 128 days in a “hyperendemic” area for Chagas disease, more than exposing him to kissing bugs. This observation conveys a likely additional source of infection than previously considered, which might reinforce the idea that Chagas disease contributed to Darwin’s manifest physical deterioration.

Resumo Os helmintos parasitas não são um componente ainda bem conhecido da biodiversidade animal. Neste trabalho, descreveu-se e comparou-se as redes de endoparasitas de três espécies de roedores nativos de um ecossistema mediterrâneo semiárido. No estudo foram detectadas um total de oito de espécies de helmintos gastrointestinais parasitas. As comunidades endoparasíticas dos roedores Phyllotis darwini (5 espécies), Octodon degus (4 espécies) e Abrothrix olivaceus (3 espécies) foram descritas por meio da sua prevalência e abundância média. Além disso, os registros de endoparasitas achados nas diferentes espécies de roedores foram submetidos a uma análise de rarefação para verificar a robustez da amostragem, e utilizados para comparar a riqueza e a similaridade entre espécies de roedores. Octodon degus apresentou a maior prevalência e carga parasitária, menor diversidade, enquanto P. darwini apresentou a maior diversidade, mas uma baixa prevalência. Porém, A. olivaceus apresentou a menor prevalência e diversidade de parásitas. Este estudo representa uma contribuição ao conhecimento da fauna endoparasitária das espécies de roedores próprias das zonas semi-áridas do Mediterrâneo chileno.

Abstract Helminth parasites are still not a well-known component of animal biodiversity. In this study, we describe and compare the endoparasite assemblages of three native rodent species from a semiarid Mediterranean ecosystem. A total of eight species of gastrointestinal helminth parasites were detected. The endoparasitic communities of the rodents Phyllotis darwini (5 species), Octodon degus (4 species), and Abrothrix olivaceus (3 species) were described in terms of their prevalence and mean abundance. In addition, endoparasite records by rodent species were submitted to rarefaction analyses to verify sampling robustness and used to compare richness and similarity among rodent species. O. degus presented the highest prevalence and parasitic load, but was of low diversity, while P. darwini presented the highest diversity, but had a low prevalence rate. Conversely, A. olivaceus presented the lowest prevalence and diversity. This study contributes to the existing knowledge of the endoparasitic fauna of rodent species from semiarid Mediterranean zones.

ABSTRACT A total of 13 individuals of the rodent Abrocoma bennetti were captured and 354 ectoparasites belonging to 10 different species were collected and analyzed. The most abundant species was the Phthiraptera Monogyropus longus (61.54%), followed by the Siphonaptera Neotyphloceras chilensis (38.46%). In this study Gyropus distinctus (15.38%) is reported as new record for A. bennetti, previously described for Octodon degus, a rodent usually living in sympatry with A. bennetti. For the first time the flea Delostichus smiti, and the mites Ornithonyssus sp. and Androlaelaps fahrenholzi are recorded in this rodent species.

RESUMEN Se capturó un total de 13 individuos del roedor Abrocoma bennetti y 354 ectoparásitos de 10 especies diferentes fueron recolectados y analizados. La especie más abundante fue el phthiraptero Monogyropus longus (61,54%), seguido por el sifonáptero Neotyphloceras chilensis (38,46%). En este estudio Gyropus distinctus (15,38%) es reportado como nuevo registro para A. bennetti, descrito previamente en Octodon degus, un roedor que usualmente vive en simpatría con A. bennetti. Se registran por primera vez la pulga Delostichus smiti y los ácaros Ornithonyssus sp. y Androlaelaps farhenholzi en esta especie de roedor.

Abstract Background: Eulychnia acida is an endemic Chilean cactus species whose fruits show several traits that, taken as a whole, are compatible with a seed dispersal syndrome by large herbivore vertebrates. Since only a few large native mammals exist in Chile at present, cactus fruit consumption and seed dispersal may be coopted by introduced mammals as predicted by Janzen and Martin's (1982) hypothesis for tropical ecosystems. Findings: We describe the current frugivore species of E. acida in a protected semiarid-Mediterranean ecosystem using field measurements and feeding experiments. In addition, to examine a potential role as seed dispersers of the cactus species, we offered fruits and performed germination tests on seeds defecated by Lama guanicoe and the introduced goat Capra a. hircus under captivity conditions. Our data indicate that while fruits of E. acida are pecked by the Chilean tinamou, Nothoprocta perdicaria, and the Chilean mockingbird, Mimus thenca, and eaten by the brush-tailed rodent, Octodon degus, none of these species could be considered a legitimate seed disperser. Unlike L. guanicoe, the goat C. a. hircus did not reduce seed germination, having a neutral effect. Conclusions: Results from this study indicate that introduced C. a. hircus was the only species showing a potential role in the seed dispersal process of E. acida. In the absence of native frugivore species, goats might play an important role in population recruitment of the endemic cactus. These results extend Janzen and Martin's(1982) anachronism hypothesis to the Chilean Mediterranean ecosystem.

Se estudiaron los visitantes de las infrutescencias de Tristerix aphyllus, un muérdago parásito de cactáceas. La mayoría de los visitantes fueron aves diurnas (cinco especies), especialmente el dispersor legítimo Mimus thenca. También se registraron dos especies de pequeños mamíferos nocturnos, llamando la atención el marsupial Thylamys elegans, cuyo rol como dispersor es aún desconocido.

We report the first record of Litomosoides pardinasi in native and exotic rodents from Chile. Litomosoides pardinasi, described in the Argentine Patagonia parasitizing Phyllotis xanthopygus and Oligoryzomys longicaudatus, was found in Chile parasitizing the peritoneal and thoracic cavities of O. longicaudatus (prevalence (P)= 18.9%, mean intensity (MI)= 57.3) and Phyllotis darwini (P= 4.2%, MI= 10), and in the peritoneal cavity of Rattus rattus (P= 1.24%; MI= 22.5). Total P in native rodents from Chile was significantly lower than in Argentina, while the total MI was higher. Prevalence and MI of L. pardinasi in O. longicaudatus from Chile and Argentina showed non-significant differences; prevalence in P. darwini from Chile was significantly lower than in P. xanthopygus from Argentina and than in Chilean O. longicaudatus. Our results, together with those from Argentina, support the hypothesis that L. pardinasi is well established in O. longicaudatus, but seems to be recently acquired by P. darwini and the exotic R. rattus. Considering the known host distribution of Litomosoides species among the sigmodontines, our results also support the hypothesis that L. pardinasi first colonized the Oryzomyini tribe and later, by different phenomena of host-switching, colonized the Phyllotini tribe and the exotic R. rattus.

Litomosoides pardinasi es registrada por primera vez en roedores nativos y exóticos de Chile. La especie Litomosoides pardinasi, parásita de Phyllotis xanthopygus y Oligoryzomys longicaudatus en la Patagonia Argentina, fue encontrada en Chile parasitando la cavidad torácica y abdominal de O. longicaudatus (prevalencia (P)= 18.9%, intensidad media (MI)= 57.3) y de Phyllotis darwini (P= 4.2%, MI= 10), y la cavidad abdominal del roedor exótico Rattus rattus (P= 1.24%; MI= 22.5). La P total en roedores nativos de Chile fue significativamente menor que la P de Argentina, en tanto la MI total fue significativamente mayor. La P y MI de L. pardinasi en O. longicaudatus de Chile y Argentina no mostraron diferencias significativas; la P en P. darwini de Chile fue significativamente menor que la de P. xanthopygus de Argentina y que la de O. longicaudatus de Chile. Considerando la distribución de las especies de Litomosoides entre los sigmodontinos, estos resultados apoyan la hipótesis que L. pardinasi está bien establecida en O. longicaudatus y que posiblemente haya sido recientemente adquirida por P. darwini y R. rattus. Así, L. pardinasi colonizó primero a la Tribu Oryzomyini y posteriormente por un fenómeno de cambio de hospedero a la Tribu Phyllotini y a R. rattus.

Pollinators are able to discriminate among different floral phenotypes. Thus, flowers more attractive to pollinators usually receive more visits to their reproductive structures. However, this effect of attraction does not necessarily occur in a binary way, all-or-nothing. Loasa tricolor KerGawl. is an annual herb covered with stinging hairs. Flowers present a corolla with five yellow petals and red nectarine scales. In this study, we assess whether the variation in the floral phenotype of L. tricolor affects discrimination by pollinators, following a dose-dependent type of response. This study was carried out in a protected area of Chile where L. tricolor shows high levels of florivory, probably affecting its attraction to pollinators. We experimentally modified the corolla phenotype, removing three or all petals. We measured visitation rate, richness and diversity of pollinator species in treated and control flowers. Results show that three-petal-removal did not reduce the visitation rate compared to control, while complete-petal-removal significantly reduced the visitation rate. Most pollinator species were recorded in the three-petal-removal treatment (nine species), while complete-petal-removal treatment obtained the lowest richness value (four species). These results suggest that species diversity, richness and visitation rates are affected by flower phenotype variation, but probably for complete petal loss only. We suggest that different levels of florivory on L. tricolor do not affect pollinator discrimination in a dose-dependent way.

Los polinizadores son capaces de discriminar entre diferentes fenotipos florales. Por lo tanto, flores más atractivas para los polinizadores usualmente reciben más visitas a sus estructuras reproductivas. Sin embargo, este efecto de atracción no ocurre necesariamente de una forma binaria, todo o nada. Loasa tricolor KerGawl. es una hierba anual cubierta con pelos urticantes. Sus flores presentan una corola con cinco pétalos amarillos y escamas nectarinas rojas. En este estudio, evaluamos si la variación en el fenotipo floral de L. tricolor afecta la discriminación por polinizadores, siguiendo una respuesta de tipo dosis-dependiente. Este estudio fue llevado a cabo en un área protegida de Chile donde L. tricolor muestra altos niveles de herbivoría floral, probablemente afectando su atracción hacia los polinizadores. Modificamos experimentalmente el fenotipo de la corola, removiendo tres o todos sus pétalos. Medimos la tasa de visita, riqueza y diversidad de especies de polinizadores en las flores tratadas y control. Nuestros resultados muestran que la remoción de tres pétalos no reduce la tasa de visita comparado con el control, mientras que la remoción de todos los pétalos reduce significativamente la tasa de visita. La mayoría de las especies de polinizadores fueron registradas en el tratamiento de remoción de tres pétalos (nueve especies), mientras que en el tratamiento de remoción de todos los pétalos se obtuvo un bajo valor de riqueza (cuatro especies). Estos resultados sugieren que la diversidad, riqueza y tasa de visita de las especies son afectadas por la variación en el fenotipo floral, pero probablemente sólo por la pérdida completa de pétalos. Nosotros sugerimos que los diferentes niveles de herbivoría floral en L. tricolor no afectan la discriminación de los polinizadores en forma dosis-dependiente.

Female fecundity increases with body size in a variety of insects, but it is unknown if this generalization applies for kissing bugs. In this study, we evaluate whether gonad weight in the bloodsucking insect Mepraia spinolai correlates with body size, or determined by nutrition or developmental time. We found that the investment on reproductive tissue correlates positively and significantly with body size and with the amount of ingested blood by female insects along their lifespan. Total molting time did not significantly affect gonad weight. We suggest that under optimal feeding conditions M. spinolai females could express their maximum reproductive potential.

Molecular evidence showed 46.2% of Trypanosoma cruzi infection in Mepraia spinolai insects from North-Central Chile, which is significantly higher than previous reports of up to 26% by microscopic observation. Our results show similar infection levels among nymphal stages, ranging from 38.3 to 54.1%, indicating that younger nymphs could be as important as older ones in parasite transmission. A cautionary note must be stressed to indicate the potential role of M. spinolai in transmitting T. cruzi in country areas due to the high infection level detected by molecular analysis.

Mepraia spinolai is a silvatic species of Triatominae which prefers microhabitats near to or in rock piles. It is also able to maintain similar or higher size populations near houses. The density of bugs in quarries near Santiago, Chile, differed within microhabitats and varied significantly within sites according to season. M. spinolai was not found in sites characterized by human perturbation of quarries. Our results confirm M. spinolai as a silvatic triatomine whose importance as a vector of Chagas disease will depend on contact with humans. This could occur if the habitats where populations of this species are found become exploited for the building of urban areas.

We present quantitative information on the natural history of a host-parasite interaction that consists on the holoparasitic mistletoe Tristerix aphyllus (Loranthaceae) and its cacti host species. More specifically, we inquire into the historical and biogeographical setting of the relationship, and quantify the autoecology of the floral biology, pollination, seed dispersal, and parasitism of the system. The impact of the mistletoe on the evolution of defense systems is evaluated both at intraspecific and interspecific levels through consideration of the potential for parasite-mediated selection and the geographical structure of the host-parasite interaction. Finally, we suggest prospective lines of research which include aspects related to: (i) the evolution of virulence, (ii) the geographic structure of the interaction, and (iii) the historical evidence for adaptation. These topics will allow us to gain a better understanding of the ecological subtlety and evolution of this singular interaction in semiarid Chile

Presentamos información cuantitativa de la historia natural de la relación parásito-hospedero constituida por el muérdago holoparásito Tristerix aphyllus (Loranthaceae) y sus hospederos cactáceas. Más específicamente, indagamos en los determinantes históricos y biogeográficos de la interacción y cuantificamos la autoecología de la biología floral, polinización, dispersión y parasitismo en este sistema. El impacto del parasitismo sobre la evolución de sistemas defensivos en las cactáceas hospederas es considerado tanto a nivel intraespecífico como interespecífico, tomando en cuenta el potencial para selección mediada por parásitos y la estructura geográfica de la interacción. Finalmente, sugerimos futuras avenidas de investigación en este sistema que incluyen los tópicos de: (i) evolución de la virulencia, (ii) estructuración de la interacción en mosaico geográfico y, (iii) pruebas históricas de adaptación. Estos aspectos permitirán adquirir un mayor conocimiento de la sutileza ecológica y de la evolución de esta especial interacción en los sistemas naturales de Chile semiárido

We describe the pattern of emergence of the holoparasitic mistletoe Tristerix aphyllus from its cactus host Echinopsis chilensis in a semiarid Chilean ecosystem. The observed circular distribution of the parasite inflorescence differed significantly from a uniform distribution based on a random process. We quantified the circular distribution of the seeds defecated on the cactus surface by Mimus thenca, the only bird responsible of seed dispersal. Our data did not support the idea of a directional seed deposition by the bird. To test the hypothesis that the observed circular distribution can be attributable to a differential seed survival due to microsite temperature variation, we infected cacti with seeds of T. aphyllus every 30ºand quantified the temperature associated to each angle. Our results revealed that even though seeds located in angles with higher sun exposure had the lowest haustorial disk formation, this variation in mortality is not sufficient to explain the angular polarity observed in this species. Inspection of inflorescences of T. aphyllus that emerged 17 months after the experimental infection, revealed mean angular values indistinguishable from the natural circular distribution. Assessment of the anatomical structure at two opposing angles of the cactus revealed striking differences in epidermal constitution, such as a four-fold thicker epidermis in north than in south facing samples due to formation of highly lignified bark. We suggest that bark formation is likely the most important factor determining the biased circular distribution of T. aphyllus

Describimos el patrón de emergencia del muérdago holoparásito Tristerix aphyllus desde su cacto hospedador Echinopsis chilensis en un ecosistema semiárido de Chile. La distribución circular de las inflorescencias del parásito difirió significativamente de una distribución uniforme basada en un proceso aleatorio. Cuantificamos la distribución circular de las semillas defecadas sobre la superficie del cacto por el mímido Mimus thenca, el único ave responsable de la dispersión del muérdago. Nuestros datos no sostuvieron la idea de una deposición de semillas direccional por parte del ave. Para someter a prueba la hipótesis que la distribución circular observada es atribuible a una sobrevivencia diferencial de las semillas debido a variación térmica entre micrositios, infectamos cactos con semillas de T. aphyllus cada 30º y evaluamos la temperatura asociada a cada ángulo. Aun cuando las semillas ubicadas en ángulos con mayor exposición solar presentaron la menor formación de disco haustorial, esta variación en mortalidad no fue suficiente para dar cuenta de la polaridad angular observada. No obstante, las inflorescencias de T. aphyllus que emergieron 17 meses después de la infección experimental, revelaron estadígrafos circulares indistinguibles de aquellos observados en la situación natural. La inspección de la estructura anatómica en dos ángulos opuestos de la cactácea reveló diferencias en la constitución de la epidermis, observándose un espesor en promedio cuatro veces mayor en las muestras orientadas hacia el norte que en las orientadas hacia el sur debido a la formación de corteza altamente lignificada. Sugerimos que la formación de corteza es probablemente el factor más importante en determinar la distribución circular sesgada de T. aphyllus