Efectos de la competencia larvaria intraespecífica de Aedes aegypti y Aedes albopictus en condiciones de laboratorio / Effects of intraspecific larval competence of Aedes aegypti and Aedes albopictus under laboratory conditions

RESUMEN Introducción: Aedes aegypti y Aedes albopictus constituyen dos de las especies más importantes de mosquitos, debido a que son vectores primarios de enfermedades emergentes y reemergentes que representan una amenaza significativa para la salud pública. Objetivo: Evaluar el efecto de la competencia larvaria intraespecífica causada por baja y alta densidad de dos poblaciones de Ae. aegypti y Ae. albopictus sobre aspectos de su ciclo de vida en condiciones de laboratorio. Métodos: Se utilizaron dos poblaciones de mosquitos, Ae. aegypti y Ae. albopictus, ambas colectadas en estado de larva en el Reparto Juan de Dios Fraga, La Lisa, La Habana, Cuba. Se establecieron condiciones de baja (70 larvas) y alta densidad larvaria (140 larvas) en cada réplica para cada una de las especies. Se emplearon larvas desde el primer estadio, que se siguieron hasta la formación de los adultos. Se evaluaron las variables duración del ciclo larvario, supervivencia larvaria, así como talla y supervivencia de hembras adultas, respectivamente. Resultados: Se encontró que las variables evaluadas no se afectaron en condiciones de baja densidad larvaria. Sin embargo, el efecto de la relación larvaria intraespecífica bajo condiciones de alta densidad presentada en los hábitats de Ae. aegypti y Ae. albopictus tuvo un efecto negativo en cada una de las variables del ciclo de vida evaluadas. Conclusiones: Estas alteraciones observadas son importantes dentro de los componentes de la capacidad vectorial, con implicaciones en la epidemiología de las enfermedades transmitidas por estos mosquitos. Los resultados pudieran extrapolarse al comportamiento de estos mosquitos en su entorno natural. Estas condiciones podrían aumentar los patrones de transmisión del virus del dengue, así como un mayor riesgo de infección para la población humana.

ABSTRACT Introduction: Aedes aegypti and Aedes albopictus are two of the most important mosquito species, since they are the main vector of emerging and re-emerging diseases that represent a significant threat to public health. Objective: To evaluate the effect of intraspecific larval competence caused by low and high density in two populations of Ae. aegypti and Ae. albopictus on aspects of their life cycles under laboratory conditions. Methods: Two mosquitos populations were used, Ae. aegypti and Ae. albopictus, both collected during their larval stage in Juan de Dios Fraga town, La Lisa, Havana, Cuba. Low (70 larvae) and high (140 larvae) density conditions were established in each replication for each species. Larvae from the first stage were used and follow-up was established until adults emerged. Variables such as: larval cycle duration, larval survival, and adult female size and survival were evaluated. Results: The variables evaluated were not affected under low larval density conditions. However, the intraspecific larval relationship under high density conditions in Ae. aegypti and Ae. albopictus habitats had a negative effect in each of the variables of the life cycles. Conclusions: The observed alterations are important within the components of vectorial capacity, with implications for the epidemiology of these mosquitos-borne diseases. The results could be extended to the behavior of these mosquitoes in their natural environment. These conditions could increase the transmission patterns of dengue virus and the risk of infection for the human population.

Modeling of Equivalent Effective Temperature and its possible incidence on larval density of Anopheles mosquitoes (Diptera: Culicidae) in Villa Clara province, Cuba / Modelación de la Temperatura Efectiva Equivalente y posible incidencia en la densidad larval de mosquitos Anopheles (Diptera: Culicidae) en la provincia Villa Clara, Cuba

AbstractThe wind chill or Equivalent Effective Temperature (EET) is the thermic sensation that a person feels when being exposed to a certain combination of temperature from the air, relative humidity and wind velocity. The objective of this investigation was directed to determine the possible incidence of the EET upon the larval density of Anopheles mosquitoes in Villa Clara province, Cuba. The Climatological data were compiled from the Yabú station in Santa Clara, and a total of 5 370 measurements were included in a database every three hours, using the aggregate function of the Statistical Package of Social Science software version 13 (SPSS), from January 1st, 2011 to September 30th, 2013. A long term forecast (1 year of advance) was made to obtain EET and the Anopheles larval density in the locality of Santo Domingo was modelled. These entomological data were taken at the same time but monthly, so the EET data were converted to monthly scale to be correlated with the monthly data of the larval density. The result was a 97.1 % of variance with a standard error (SE) of 3.57 °C for the model of the EET with a year of anticipation; therefore, the tendency in time was significant. The modeling also included the Anopheles larval density of mosquitoes in Santo Domingo, Villa Clara province, observing an increase of the EET, while the Anopheles mosquito larvae also increased. The most important variables in the model were the EET that were back in 1, 2, 3, 4, 7, 16, 24, 40 for the previous year; that is to say 2 920, 2 921, and so on, which explained a strong contagion among the data. EET correlation compared with itself in previous year was high; therefore, it may be used as a predictable variable. The anophelinic density in Santo Domingo explained the 66 % of the variance, with a SE of 0.66 larvae.m-2. The tendency of the Anopheles larval density was to diminish. In conclusion, EET has an important impact in larval density of Anopheles with EET increase associated with larval density decrease.

ResumenLa Temperatura Efectiva Equivalente (TEE) es la sensación térmica que siente una persona frente a una determinada combinación de temperatura del aire, humedad relativa y velocidad del viento. El objetivo de la investigación fue determinar la posible incidencia de la TEE sobre la densidad larval de mosquitos del género Anopheles en la provincia Villa Clara, Cuba. Una base de datos recogió medidas climatológicos cada tres horas durante el periodo comprendido entre el 1 de enero 2011 hasta el 30 de septiembre 2013, proveyendo un total de 5 370 medidas de la estación Yabú de Santa Clara. Se realizó un pronóstico a largo plazo (1 año) para obtener la TEE y se modeló la densidad larvaria total de mosquitos en la localidad de Santo Domingo. Los datos entomológicos fueron recogidos en el mismo lapso temporal pero con una periodicidad mensual, por lo que los datos de TEE fueron convertidos a escala mensual para poder ser empleados con los datos de densidad larvaria. Para la modelación se utilizó la Metodología de Regresión Objetiva Regresiva que explicó el 97.1 % de varianza con un error estándar (SE) de 3.57 ºC para el modelo de TEE con un año de antelación; la tendencia en el tiempo fue significativa al aumento. Además, al modelar la densidad larvaria anofelínica en el municipio Santo Domingo, se observó que a medida que aumenta la TEE, disminuye la densidad larval anofelínica. La variable más importante en el modelo fue la TEE regresada en 1, 2, 3, 4, 7, 16, 24, 40, pero del año anterior, es decir 2 920, 2 921, y así sucesivamente, explicando un contagio muy fuerte entre los datos. Ello fue debido a que la correlación de TEE con ella misma en años anteriores fue alta, por lo que puede ser utilizada como variable predictora. El modelo de densidad larval anofelínica en Santo Domingo explicó el 66 % de la varianza, con un SE de 0.06 larvas/m2. La tendencia de la DLA fue a la disminución. En conclusión, la TEE tuvo una incidencia directamente proporcional en la densidad larval anofelínica, ya que a medida que aumentaba este indicador, disminuyó la densidad larval anofelínica.

Competição entre larvas de Aedes aegypti e Aedes albopictus em laboratório / Competition between Aedes aegypti and Aedes albopictus larvae in the laboratory

Este estudo teve como objetivo avaliar os efeitos da competição larval intra e interespecífica entre Aedes aegypti e Aedes albopictus, sobre sobrevivência de larvas, tempo de desenvolvimento e comprimento de asa. O experimento foi realizado em três densidades com 5 proporções das espécies. A sobrevivência de Aedes aegypti apresentou-se superior a de Aedes albopictus em densidade intermediária e inferior em densidade alta. Somente Aedes albopictus teve seu tempo de desenvolvimento afetado. Diferenças encontradas nas comparações das combinações das espécies demonstraram que o comprimento médio de asas de Aedes aegypti, no geral, foi maior que Aedes albopictus. Nas duas espécies, a competição afetou mais o comprimento de asa e a sobrevivência que o tempo de desenvolvimento. Aedes aegypti parece apresentar maior capacidade competitiva em relação a Aedes albopictus em densidade intermediária.

This study had the aim of evaluating the effects of intra and interspecies larval competition between Aedes aegypti and Aedes albopictus, survival of larvae time taken to develop and wing length. The experiment was carried out with three densities and five proportions of the species. Aedes aegypti survival was greater than Aedes albopictus survival at intermediate density, while it was lower at high density. Only the time taken for Aedes albopictus to develop was affected. The differences found in comparing the species combinations demonstrated that the mean wing length of Aedes aegypti was generally greater than that of Aedes albopictus. For both species, competition had greater effect on wing length and survival than on the time taken to develop. Aedes aegypti seems to present better competitive capacity than does Aedes albopictus, at intermediate density.

Seasonal variation in larval density of Limnoperna fortunei (Bivalvia, Mytilidae) in the Iguaçu and Paraná rivers, in the region of Foz do Iguaçu, Paraná, Southern Brazil

The larval density of the invasive mussel Limnoperna fortunei (Bivalvia, Mytilidae) was monitored from January 2005 to February 2006 at two points along the Paraná and the Iguaçu Rivers, near Foz do Iguaçu, PR, Brazil. The results indicated two density peaks in the Paraná River: a lower peak between March and June and a higher peak in October. In the Iguaçu River, the values were much lower, yet they also showed a peak between September and October. A reduction in the reproductive activity was observed in both the rivers between July and August. The average larval density at the collection point in the Paraná reached 948.5 larvae/m³, with a peak of 2,999.5 larvae/m³ in October. The present study represented the first quantification of the larval density of L. fortunei in the lower reaches of the Iguaçu River, downstream of the Iguaçu falls.

A densidade larval do molusco invasor Limnoperna fortunei (Bivalvia, Mytilidae) foi monitorada entre janeiro de 2005 e fevereiro de 2006 em dois pontos dos rios Paraná e Iguaçu, na região de Foz do Iguaçu, PR. Os resultados registraram dois picos de densidade no rio Paraná: entre março e junho e um maior em outubro. No rio Iguaçu, os valores foram muito inferiores, mas também com um pico entre setembro-outubro. Em ambos os rios foi verificada uma pausa reprodutiva entre os meses de julho-agosto. A densidade média de larvas de L. fortunei no ponto amostrado no rio Paraná chegou a 948.5 larvas/m³, com pico de 2.999,5 larvas/m³ em outubro. O presente estudo representa a primeira quantificação da densidade larval de L. fortunei no rio Iguaçu, a jusante das Cataratas do Iguaçu.