Redução do forrageio do iguana-negro-de-cauda-espinhosa, Ctenosaura similis (Sauria: Iguanidae), na presença de estímulos do predador

The presence of a predator may have direct and indirect effects on the behavior of the prey. Although altered behavior may help prey avoid predators, it also can have a potential impact on critical activities such as foraging. Predator-prey interactions are routinely studied in laboratory-based experiments owing to the perceived difficulties of conducting such experiments in natural settings. We conducted an experimental study under field conditions in Palo Verde National Park in northwestern Costa Rica to assess behavioral responses of Black Spiny-tailed Iguanas (Ctenosaura similis) to the presence of predators and predator cues. Free-roaming iguanas were offered mango in designated areas in the presence of a predator (Boa constrictor), a predator cue (B. constrictor feces), and a control (no predator or predator cue). Results indicate that iguanas reduced their foraging efforts in the presence of both a predator and its cue.A presença de um predador pode exercer efeitos diretos e indiretos sobre o comportamento da presa. Embora a alteração do comportamento possa ajudar a presa a evitar predadores, pode também ter um impacto potencial sobre atividades críticas, como o forrageio. As interações predador-presa são comumente estudadas em experimentos de laboratório devido às dificuldades em conduzir experimentos sob condições naturais. Conduzimos um estudo experimental em campo no Parque Nacional Palo Verde, no noroeste da Costa Rica, para avaliar as respostas dos iguanas-negros-de-cauda-espinhosa (Ctenosaura similis) à presença de predadores e de seus estímulos. Oferecemos manga a iguanas livres em áreas pré-estabelecidas na presença de um predador (Boa constrictor), de um estímulo do predador (fezes de B. constrictor) e em uma áreacontrole (sem predador ou estímulo). Os resultados indicam que os iguanas reduziram seus esforços de forrageio tanto na presença do predador como de seu estímulo

Habitat use and age structure of the Fer-de-Lance (Bothrops asper, Viperidae) in Braulio Carrillo National Park, Costa Rica

The Fer-de-lance or terciopelo (Bothrops asper) inhabits a wide range of environmental conditions and habitats across Central America. While much information on the species is based on anecdotal observations and museum specimens, data collected under natural conditions are more limited. To better document its natural history, this study sought to determine the habitat use and age structure of B. asper in the Quebrada Gonzalez sector of Braulio Carrillo National Park, Costa Rica. Snake surveys were conducted from January 2015 to August 2017 and used to evaluate the population age-class distribution and sex ratio. To evaluate macrohabitat use, surveys were conducted in four habitat types (mature forest, late succession, early succession, and human infrastructure). Microhabitat use was determined by recording several structural variables at each snake location and at random sites. Amphibians were sampled in each habitat type to evaluate the available prey base. Fifty-five individuals were captured, mostly females and juveniles, with five recaptures. Snakes were encountered in all habitat types but most often in early succession forests, which have dense vegetation cover and high prey availability. Snakes selected areas with heavy understory cover when resting, and more exposed sites, often closer to bodies of water, when ambushing prey or moving. Human-disturbed sites were used least. Although snake encounters did tend to correlate with higher amphibian abundance, other factors such as mammalian prey abundance could also influence snake distribution.El Fer-de-lance o terciopelo (Bothrops asper) habita una amplia gama de condiciones ambientales y hábitats en América Central. Si bien gran parte de la información sobre la especie se basa en observaciones anecdóticas y especímenes de museos, los datos recopilados en condiciones naturales son más limitados. Para documentar mejor su historia natural, este estudio buscó determinar el uso del hábitat y la estructura de edad de B. asper en el sector Quebrada González del Parque Nacional Braulio Carrillo, Costa Rica. Las encuestas sobre serpientes se realizaron entre enero de 2015 y agosto de 2017 y se utilizaron para evaluar la distribución por clases de edad y la proporción de sexos de la población. Para evaluar el uso del macrohábitat, se realizaron estudios en cuatro tipos de hábitat (bosque maduro, sucesión tardía, sucesión temprana e infraestructura humana). El uso de microhábitats se determinó registrando varias variables estructurales en cada ubicación de serpiente y en sitios aleatorios. Se tomaron muestras de anfibios en cada tipo de hábitat para evaluar la base de presas disponibles. Se capturaron 55 individuos, en su mayoría hembras y juveniles, con cinco recapturas. Las serpientes se encontraron en todos los tipos de hábitats, pero con mayor frecuencia en los bosques de sucesión temprana, que tienen una densa cobertura vegetal y una alta disponibilidad de presas. Las serpientes seleccionaron áreas con una cubierta densa del sotobosque cuando descansaban y sitios más expuestos, a menudo más cerca de cuerpos de agua, cuando emboscaban a sus presas o se movían. Los sitios perturbados por humanos fueron los menos utilizados. Aunque los encuentros con serpientes tienden a correlacionarse con una mayor abundancia de anfibios, otros factores como la abundancia de presas de mamíferos también podrían influir en la distribución de las serpientes.Universidad Nacional, Costa Rica.Universidad Técnica Nacional, Costa RicaUniversidad de Hartford, Estados Unidos.Escuela de Ciencias Biológica

Reduced foraging in the presence of predator cues by the Black Spiny-tailed Iguana, Ctenosaura similis (Sauria: Iguanidae)

The presence of a predator may have direct and indirect effects on the behavior of the prey. Although altered behavior may help prey avoid predators, it also can have a potential impact on critical activities such as foraging. Predator-prey interactions are routinely studied in laboratory-based experiments owing to theperceived difficulties of conducting such experiments in natural settings. We conducted an experimental study under field conditions in Palo Verde National Park in northwestern Costa Rica to assess behavioral responses of Black Spiny-tailed Iguanas (Ctenosaurasimilis) to the presence of predators and predator cues. Free-roaming iguanas were offered mango in designated areas in the presence of a predator (Boa constrictor), a predator cue (B. constrictor feces), and a control (no predator or predator cue). Results indicate that iguanas reduced their foraging efforts in the presence of both a predator and its cue

Snake diversity (squamata: Serpentes) in Quebrada González sector of Braulio Carrillo National Park, Costa Rica

Within Braulio Carrillo National Park (BCNP) of Costa Rica, there is a lack of quantitative data regarding the snake community despite its informally reported abundance and relevance to human health. The objective of this research was to document the diversity of snakes within the Quebrada González sector of BCNP. We searched for snakes using visual encounter surveys along several trails, as well as in quadrants and transects within the forest interior. We captured 272 individual snakes across 28 species and five families. Bothrops asper (Fer-de-Lance) and Bothriechis schlegelii (Eyelash Viper), both Viperids, were the most abundant species encountered, most likely due to their generalist habits. Most other snake species were found in smaller numbers but with roughly equal frequency to each other. Snake species richness and relative abundance were similar between the sampled trails but did show temporal variation during the study period with higher values during the rainy season from April to August. Species composition between the sampled trails was similar, but we did detect some differences likely due to differing habitat characteristics. The species diversity identified here may have been positively affected by the location of the site along an elevational and habitat gradient with high temperatures and precipitation, but likely remains incomplete due to the preliminary nature of the survey and the difficulty of detecting many snake species. A species accumulation curve suggests that the inventory was approximately 81% complete; additional, less abundant species would likely be identified with increased sampling effort and additional survey techniquesEn el Parque Nacional Braulio Carrillo (PNBC) existe una carencia de datos cuantitativos de la comunidad de serpientes presentes, a pesar de su abundancia e importancia médica reportada informalmente. El objetivo de este estudio fue documentar la diversidad de serpientes en el sector Quebrada González del PNBC. Realizamos búsquedas mediante relevamiento por encuentro visual en los senderos del parque, así como en cuadrantes y transectos en áreas dentro del bosque. Capturamos 272 individuos, pertenecientes a 28 especies y cinco familias. Bothrops asper (Terciopelo) y Bothriechis schlegelii (Bocaracá), ambas de la familia Viperidae, fueron las especies más abundantes, probablemente debido a sus hábitos generalistas. Las otras especies fueron encontradas en una abundancia menor, pero equitativa entre sí. La riqueza y abundancia relativa de las serpientes fue similar entre los senderos, sin embargo varió temporalmente durante el período de estudio con los valores más altos en la época lluviosa entre abril y agosto. La composición de especies fue similar entre los senderos, sin embargo se detectaron algunas diferencias debido probablemente a que las características del hábitat en estos difieren entre sí. La diversidad observada podría estar afectada positivamente por la presencia del sitio de estudio en un gradiente altitudinal y de hábitat, con altas temperaturas y tasas de precipitación, sin embargo aún es incompleto debido a su naturaleza preliminar y a la dificultad de observar algunas especies de serpiente. La curva de acumulación de especies muestra que se completó el 81% del inventario; adicionalmente, podrían encontrarse especies menos abundantes si se aumentara el esfuerzo y se diversificaran las técnicas de muestreoUniversidad Nacional, Costa RicaUniversidad Técnica Nacional, Costa RicaUniversity of Hartford, Estados UnidosEscuela de Ciencias Biológica

A Comprehensive Analysis of Replicative Lifespan in 4,698 Single-Gene Deletion Strains Uncovers Conserved Mechanisms of Aging

Many genes that affect replicative lifespan (RLS) in the budding yeast Saccharomyces cerevisiae also affect aging in other organisms such as C. elegans and M. musculus. We performed a systematic analysis of yeast RLS in a set of 4,698 viable single-gene deletion strains. Multiple functional gene clusters were identified, and full genome-to-genome comparison demonstrated a significant conservation in longevity pathways between yeast and C. elegans. Among the mechanisms of aging identified, deletion of tRNA exporter LOS1 robustly extended lifespan. Dietary restriction (DR) and inhibition of mechanistic Target of Rapamycin (mTOR) exclude Los1 from the nucleus in a Rad53-dependent manner. Moreover, lifespan extension from deletion of LOS1 is nonadditive with DR or mTOR inhibition, and results in Gcn4 transcription factor activation. Thus, the DNA damage response and mTOR converge on Los1-mediated nuclear tRNA export to regulate Gcn4 activity and aging