Paley's watchmaker analogy and prebiotic synthetic chemistry in surfactant assemblies. Formaldehyde scavenging by pyrroles leading to porphyrins as a case study.

The formation of elaborate molecules is regarded as an essential first step in prebiotic chemistry, but how such transformations could spontaneously occur, particularly in dilute aqueous conditions, remains poorly understood. Here, micromolar concentrations of a 3,4-dialkylpyrrole and excess formaldehyde in aqueous micellar solution (pH 7) at 25 or 50 °C were found to give good yield (up to 40%) of the lipophilic octaalkylporphyrin. The reaction occurs despite a mean occupancy number of ∼0.1 pyrrole molecules/micelle, and <1 of 10,000 micelles initially containing the requisite 4 pyrrole molecules to form the porphyrin assuming a (random) Poisson distribution. Yields of up to 13% were observed in large, unilamellar phosphatidylcholine vesicles, wherein there are ∼15,000 pyrrole molecules per vesicle membrane. Double-labeling crossover experiments (of 3,4-diethylpyrrole and 3,4-dimethylpyrrole) examined by mass spectrometry revealed facile exchange processes of reactive constituents among both micelle and vesicle surfactant assemblies. Together, the exchange of pyrrolic reactants among micelles and the thermodynamic driving force for tetrapyrrole formation overcome the apparent statistical odds against reaction. The fruitful exchange, accumulation and reaction of minute quantities of reactants in aqueous-surfactant assemblies suggest a general means for formation of prebiotically valuable constituents, even when the statistical odds at the outset are overwhelmingly improbable.

Mosquito population dynamics is shaped by the interaction among larval density, season, and land use.

Understanding how variation in key abiotic and biotic factors interact at spatial scales relevant for mosquito fitness and population dynamics is crucial for predicting current and future mosquito distributions and abundances, and the transmission potential for human pathogens. However, studies investigating the effects of environmental variation on mosquito traits have investigated environmental factors in isolation or in laboratory experiments that examine constant environmental conditions that often do not occur in the field. To address these limitations, we conducted a semi-field experiment in Athens, Georgia using the invasive Asian tiger mosquito (Aedes albopictus). We selected nine sites that spanned natural variation in impervious surface and vegetation cover to explore effects of the microclimate (temperature and humidity) on mosquitoes. On these sites, we manipulated conspecific larval density at each site. We repeated the experiment in the summer and fall. We then evaluated the effects of land cover, larval density, and time of season, as well as interactive effects, on the mean proportion of females emerging, juvenile development time, size upon emergence, and predicted per capita population growth (i.e., fitness). We found significant effects of larval density, land cover, and season on all response variables. Of most note, we saw strong interactive effects of season and intra-specific density on each response variable, including a non-intuitive decrease in development time with increasing intra-specific competition in the fall. Our study demonstrates that ignoring the interaction between variation in biotic and abiotic variables could reduce the accuracy and precision of models used to predict mosquito population and pathogen transmission dynamics, especially those inferring dynamics at finer-spatial scales across which transmission and control occur.

Para poder predecir la distribución y abundancia de las poblaciones de mosquitos y la transmisión potencial de patógenos a humanos, es crucial comprender cómo factores abióticos y bióticos clave para el éxito reproductivo y la dinámica poblacional de los mosquitos interactúan a escalas relevantes. Sin embargo, los estudios que han investigado los efectos de variables ambientales en las características demográficas de los mosquitos han considerado su efecto de forma aislada o en experimentos de laboratorio bajo condiciones ambientales constantes que, a menudo, no reflejan lo que ocurre en el campo. Para abordar estas limitaciones, llevamos a cabo un experimento de semi-campo en Athens, Georgia, utilizando el mosquito invasor tigre asiático (Aedes albopictus). Seleccionamos nueve sitios que abarcaban variaciones naturales en la superficie impermeable y cobertura vegetal para explorar los efectos del microclima (temperatura y humedad) en los mosquitos. También manipulamos la densidad de larvas de tigre asiático en dos experimentos que fueron realizados en el verano y otoño. Evaluamos los efectos de la cobertura vegetal, la densidad de larvas, la temporada climática, y la interacción entre estas variables en la proporción de hembras que emergieron, el tiempo de desarrollo de las larvas, el tamaño al momento de la emergencia, y el crecimiento demográfico per cápita previsto (éxito reproductivo). Encontramos efectos significativos de la densidad de larvas, la variación de la cobertura vegetal y la estación del año en todas las variables de respuesta. Más notablemente, observamos un fuerte efecto de la interacción entre la temporada climática y la densidad de larvas en todas las variables de respuesta, incluyendo una disminución no intuitiva en el tiempo de desarrollo con el aumento de la competencia intraespecífica en el otoño. Nuestro estudio evidencia que ignorar la interacción entre variables abióticas y bióticas podría reducir la exactitud y precisión de los modelos utilizados para predecir las dinámicas de las poblaciones de mosquitos, y por tanto, de la transmisión de patógenos. Esto, especialmente en modelos que infieren estas dinámicas a escalas espaciales más finas, en las cuales ocurre la transmisión y el control.

Microclimate and Larval Habitat Density Predict Adult Aedes albopictus Abundance in Urban Areas.

The Asian tiger mosquito, Aedes albopictus, transmits several arboviruses of public health importance, including chikungunya and dengue. Since its introduction to the United States in 1985, the species has invaded more than 40 states, including temperate areas not previously at risk of Aedes-transmitted arboviruses. Mathematical models incorporate climatic variables in predictions of site-specific Ae. albopictus abundances to identify human populations at risk of disease. However, these models rely on coarse resolutions of environmental data that may not accurately represent the climatic profile experienced by mosquitoes in the field, particularly in climatically heterogeneous urban areas. In this study, we pair field surveys of larval and adult Ae. albopictus mosquitoes with site-specific microclimate data across a range of land use types to investigate the relationships between microclimate, density of larval habitat, and adult mosquito abundance and determine whether these relationships change across an urban gradient. We find no evidence for a difference in larval habitat density or adult abundance between rural, suburban, and urban land classes. Adult abundance increases with increasing larval habitat density, which itself is dependent on microclimate. Adult abundance is strongly explained by microclimate variables, demonstrating that theoretically derived, laboratory-parameterized relationships in ectotherm physiology apply to the field. Our results support the continued use of temperature-dependent models to predict Ae. albopictus abundance in urban areas.