Aedes aegypti: egg morphology and embryonic development

Abstract

Background The diseases for which Aedes aegypti is a vector are worrisome. The high vector competence of this mosquito, as well as its anthropophilia and ability to adapt to the urban environment, allows it to exploit many habitats, making its prevention an arduous task. Despite current disease control measures focused on the mosquito, the effectiveness in containing its dispersion still requires improvement; thus greater knowledge about this insect is fundamental. Methods Aedes aegypti egg morphology and embryonic development were analyzed from eggs of the insectary of the Institute of Biomedical Sciences of the University of São Paulo. Optical (light and confocal) and electronic (transmission and scanning) microscopy were used to analyze the morphological and ultrastructural features of the eggs. Embryos were observed in the initial (0–20.5 h after egg-laying), intermediate (20.6–40.1 h after egg-laying), and final (40.2–61.6 h) stages of development, and kept at a temperature of 28 °C ± 1 °C until collection for processing. Results Eggs of Ae. aegypti were whitish at the time of oviposition, and then quickly became black. The egg length was 581.45 ± 39.73 μm and the width was 175.36 ± 11.59. Access to the embryo was difficult due to the egg morphology, point of embryonic development, and difficult permeability of the exochorion (mainly in fixation). Only about 5% of the collected eggs were successfully processed. In the initial stage of embryonic development, characteristics suggestive of intense cellular activity were found. In the intermediate stage, the beginning of the segmentation process was evident. In the final phase, it was possible to differentiate the cephalic region and the thoracic and abdominal segments. Conclusion The chorion was found to be an important protective barrier and a limiting factor for the evaluation of the embryos and mosquito embryonic cells, indicating that further studies need to be carried out to identify the reason that this occurs. Graphical abstract

Ovicidal toxicity of plant essential oils and their major constituents against two mosquito vectors and their non-target aquatic predators

“…On egg morphology, its SEM images in Figs. 1 and 2 show damages to the exochorionic meshwork and tubercles of the outer cells on exochorion cuticle (external chitin layer) with cell borders, papillae, and aeropyles 40,41 . Moreover, the cell borders and papillae as well as aeropyles were covered with a layer that was assumed to be an oil layer, which would explain the ovicidal mechanism of the EO, discussed in the paragraph below.…”

The impact of radiofrequency exposure on Aedes aegypti (Diptera: Culicidae) development

“…and Bova et al . [ 25 , 28 ]. The differences observed were ascribed to variations in geographical origin, topographical features of the study sites, diverse climatic conditions, and other contributing factors.…”

“…This study also revealed that the eggs from the laboratory and field strains for all groups highlighted narrower dimensions, which contradicted studies by Suman et al ., Mundim-Pombo et al ., and Win et al . [ 24 , 25 , 29 ]. In contrast, the egg index values in this study closely resembled the findings of Mundim-Pombo et al .’s study [ 25 ].…”

“…The egg length was determined as the distance between the anterior and posterior poles, while the egg width was measured at the widest point [ 24 ]. Alternatively, the egg index was calculated based on the length-to-width ratio, while the surface area was automatically estimated using Image J [ 25 ].…”

Whole-transcriptome profiling across different developmental stages of Aedes albopictus (Diptera: Culicidae) provides insights into chitin-related non-coding RNA and competing endogenous RNA networks

“…As a holometabolous insect, the biological cycle of A. albopictus involves egg, larval, pupal, and adult stages. Embryogenesis of the mosquito is a complex process involving rapid cell proliferation and organogenesis [ 46 ]. Therefore, it makes sense that a relatively high proportion of differentially expressed genes (DEGs) and more complex ceRNA networks were identified in the E vs. L1 comparison group.…”