The influence of parasites on host reproduction has been widely studied in natural and experimental conditions. Most studies, however, have evaluated the parasite impact on female hosts only, neglecting the contribution of males for host reproduction. This omission is unfortunate as sex‐dependent infection may have important implications for host–parasite associations. Here, we evaluate for the first time the independent and nonindependent effects of gender infection on host reproductive success using the kissing bug Mepraia spinolai and the protozoan Trypanosoma cruzi as model system. We set up four crossing treatments including the following: (1) both genders infected, (2) both genders uninfected, (3) males infected—females uninfected, and (4) males uninfected—females infected, using fecundity measures as response variables. Interactive effects of infection between sexes were prevalent. Uninfected females produced more and heavier eggs when crossed with uninfected than infected males. Uninfected males, in turn, sired more eggs and nymphs when crossed with uninfected than infected females. Unexpectedly, infected males sired more nymphs when crossed with infected than uninfected females. These results can be explained by the effect of parasitism on host body size. As infection reduced size in both genders, infection on one sex only creates body size mismatches and mating constraints that are not present in pairs with the same infection status. Our results indicate the fitness impact of parasitism was contingent on the infection status of genders and mediated by body size. As the fecundity impact of parasitism cannot be estimated independently for each gender, inferences based only on female host infection run the risk of providing biased estimates of parasite‐mediated impact on host reproduction.

ABSTRACT. This report offers a macroscopic and histological description of ulcerative gastric lesions in Humboldt penguins associated with the presence of Contracaecum pelagicum. Parasites of this genus have been isolated from different species of marine mammals and birds, including penguins, demonstrating its capacity to generate ulcerative lesions in the gastrointestinal tracts of many hosts. A bibliographic review revealed no publications on gastric ulceration by nematodes in Humboldt penguins. Studies carried out in Chile concerning gastrointestinal parasitism by nematodes of the Contracaecum genus in S. humboldti only established the parasite's taxonomy. This is the first pathological description of a parasitic ulcerative manifestation in the stomach of S. humboldti in the world. The Humboldt penguin is a vulnerable species. Therefore, this study is relevant as it offers a better understanding of the diseases that affect S. humboldti and facilitates the development of strategies intended to recover the population. Keywords: Spheniscus humboldti, Humboldt penguin, ulcer, stomach, Contracaecum, Chile. Primera descripción patológica de úlceras gástricas parasitarias en el pingüinode Humboldt (Spheniscus humboldti) en la costa centro-sur de Chile RESUMEN. El presente trabajo ofrece una descripción macroscópica e histológica de lesiones gástricas de tipo ulcerativas en el pingüino de Humboldt asociadas a la presencia de Contracaecum pelagicum. Parásitos del género Contracaecum han sido aislados de diferentes especies de mamíferos y aves marinas, incluyendo pingüinos, en gran parte del mundo, demostrando una gran capacidad de generar lesiones ulcerativas en un número importante de hospederos. La revisión bibliográfica reveló la ausencia de publicaciones relativas a cuadros ulcerativos gástricos causados por nemátodos en el pingüino de Humboldt. Los estudios realizados en Chile concernientes a parasitismo gastrointestinal por nemátodos del género Contracaecum en S. humboldti sólo han abordado aspectos taxonómicos. Esta publicación constituye la primera descripción patológica de un cuadro de ulceraciones gástricas parasitarias en el pingüino de Humboldt. S. humboldti está catalogado como especie vulnerable por lo que este estudio es relevante en cuanto a incrementar el entendimiento de las patologías que afectan a la especie facilitando el desarrollo de estrategias tendientes a la recuperación de la población.

RESUMENSe analizó la conducta de depredación de hembras adultas de Nabis punctipennis Blanchard (Nabidae) hacia Acyrthosiphon pisum Harris (Aphididae) en laboratorio para determinar su respuesta funcional y su potencial como agente de control biológico de este áfido. Ambos hemípteros son comunes en alfalfa, Medicago sativa L., en Chile. Las hembras de N. punctipennis presentaron una respuesta funcional tipo II, con un tiempo de manipulación de 2,757 ± 0,1181 h presa -1 y una tasa de búsqueda de 0,353 ± 0,3214 h -1 .Palabras clave: pulgón de la alfalfa, respuesta funcional, control natural, nábido de alas punteadas. ABSTRACTThis study analyzed the predatory behavior of adult females of Nabis punctipennis Blanchard (Nabidae) towards Acyrthosiphon pisum Harris (Aphididae) in the laboratory in order to determine its functional response and potential as a biological control agent of this aphid. Both hemipterans are common in alfalfa, Medicago sativa L., in Chile. The females of N. punctipennis presented a type II functional response, with a handling time of 2.757 ± 0.1181 h prey-1 and a searching rate of 0.353 ± 0.3214 h -1 .