Abstract Acetylcholinesterase is an enzyme whose main function is to terminate the transmission of nerve impulses in the cholinergic synapse in insects through the hydrolysis of acetylcholine. However, frequent applications of insecticides can select for individuals with an alteration in the enzyme and functional changes that result in an insensitivity to insecticides. In Mexico, the current strategy to combat insect vectors such as Culex quinquefasciatus is based mainly on the use of synthetic insecticides. The use of these chemicals in health and agricultural practices may also contribute to mosquito insensitivity to several groups of insecticides. Therefore, it is considered necessary to determine if there is any physiological mechanism associated with resistance. For this reason, the objective of this research was to identify if there is insensitivity of acetylcholinesterase to insecticides in Cx. quinquefasciatus populations, collected in urban and rural areas of the State of Yucatán, Mexico. Enzymatic tests were carried out with slight modifications to the established protocols. Areas were identified with mosquito populations showing acetylcholinesterase insensitivity to propoxur, a carbamate insecticide. We consider it important to determine the environmental factors that affect the behavior and response of mosquitoes following exposure to insecticides, and this knowledge could inform the design of efficient strategies in vector control programs.

Resumen La acetilcolinesterasa es una enzima, cuya principal función es finalizar la transmisión de los impulsos nerviosos en la sinapsis colinérgica en los insectos mediante la hidrólisis de la acetilcolina. Sin embargo, el uso frecuente de los insecticidas sintéticos, probablemente originen una alteración en la enzima y cambios funcionales conduciendo a la insensibilidad a los insecticidas neurotóxicos. En México la estrategia actual para el combate de insectos vectores como Culex quinquefasciatus, se basa principalmente en el uso de estos compuestos. El uso de estos productos químicos en áreas de la salud y prácticas agrícolas probablemente contribuye a la insensibilidad a diferentes grupos de insecticidas. Por lo tanto, se considera necesario determinar si existe algún mecanismo fisiológico asociado a la resistencia. Por tal motivo, el objetivo de esta investigación fue identificar si existe insensibilidad de la acetilcolinesterasa a insecticidas en poblaciones de Cx. quinquefasciatus, colectados en áreas urbanas y rurales en Yucatán. Se realizaron pruebas enzimáticas con ligeras modificaciones en los protocolos establecidos y se identificaron áreas con poblaciones de mosquitos con acetilcolinesterasa insensible a propoxur, que es un carbamato ampliamente utilizado en México. Con nuestro trabajo consideramos importante identificar los factores ambientales que afectan el comportamiento y respuesta de los mosquitos a los insecticidas, lo cual será de gran utilidad para el diseño eficiente de estrategias en los programas de control de vectores.

RESUMEN Los estudios taxonómicos sobre mosquitos se basan en la descripción morfológica de larvas y adultos. Sin embargo, son pocos los estudios enfocados en la descripción morfológica de los huevos a pesar de su valor taxonómico. La descripción de los huevos de mosquitos mediante microscopía electrónica de barrido (MEB) permite obtener imágenes más detalladas de la ornamentación del huevo, los cuales pueden proporcionar caracteres diagnósticos de la especie. El objetivo del trabajo fue describir los huevos de Psorophora cyanescens por MEB y proporcionar datos de fecundidad de la especie. En general, los huevos de Ps. cyanescens son de forma elíptica y muy anchos. El exocorión se caracteriza por un patrón de polígono, donde cada polígono consta de crestas longitudinales unidas por crestas cruzadas que definen áreas "hexagonales" regulares. Cada cresta longitudinal consiste en un pequeño tubérculo. Los pequeños tubérculos son irregulares, rectangulares, redondeados o tubulares. La ornamentación del exocorión también presenta largos tubérculos cónicos en toda la región del huevo. El aparato micropilar ubicado en la región anterior del huevo tiene un collar prominente, continuo y grueso. Psorophora cyanescens puso huevos maduros a los 2.5 días después de la alimentación sanguínea. El número promedio de huevos por hembra fue de 82.20 (± 13.31). Este es el primer estudio que describe la ultraestructura de la morfología de los huevos de Ps. cyanescens mediante MEB. Con el aporte del presente trabajo, son cinco las especies del género Psorophora que cuentan con la descripción de la morfología de los huevos mediante MEB: Ps. albigenu, Ps. albipes, Ps. columbiae, Ps. cyanescens, and Ps. ferox.

ABSTRACT Taxonomic studies on mosquitoes are based on the morphological description of larvae and adults. However, few studies have focused on the morphological description of eggs despite their taxonomic value. The description of mosquito eggs by scanning electron microscopy (SEM) allows more detailed descriptions of the ornamentation of the egg, which can provide diagnostic characters of the species. The objective of the work was to describe the eggs of Psorophora cyanescens by SEM and provide fecundity data for the species. In general, Ps. cyanescens eggs are elliptical and very wide. The exochorion is characterized by polygon pattern, where each polygon consists of longitudinal ridges joined by cross-ridges defining regular "hexagonal" areas. Each longitudinal ridge consisting by a small tubercle. The small tubercles are irregular, rectangular, rounded, or tubular. The ornamentation of the exochorion also has long and conical tubercles throughout the egg region. The micropylar apparatus located in the anterior region of the egg has a prominent, continuous and thickness collar. Psorophora cyanescens laid mature eggs at 2.5 days post-feeding. The mean number of eggs per female was 82.20 (± 13.31). This is the first study that describes the ultrastructure of the morphology of the eggs of Ps. cyanescens by SEM. With the contribution of the present work, there are five species of the genus Psorophora whose eggs morphology is described by SEM: Ps. albigenu, Ps. albipes, Ps. columbiae, Ps. cyanescens, and Ps. ferox.

ABSTRACT This study was designed to assess whether churches in endemic dengue districts in Merida, Mexico provide suitable breeding habitats for mosquitoes and are potential sites for dengue virus (DENV) transmission. Churches were inspected for immature and adult mosquitoes once every week from November 2015 to October 2016. A total of 10,997 immatures of five species were collected. The most abundant species were Aedes aegypti (6,051) and Culex quinquefasciatus (3,018). The most common source of immature Ae. aegypti were buckets followed by disposable containers. Adult collections yielded 21,226 mosquitoes of nine species. The most common species were Cx. quinquefasciatus (15,215) and Ae. aegypti (3,902). Aedes aegypti were found all year long. Female Ae. aegypti (1,380) were sorted into pools (166) and assayed for flavivirus RNA by RT-PCR and Sanger sequencing. Two pools were positive for DENV (DENV-1 and 2). In conclusion, we demonstrated that some churches in Merida are infested with mosquitoes all year long and they potentially serve as sites for DENV transmission and should therefore be considered for inclusion in mosquito and arboviruses control and surveillance efforts.