Transcriptional profiling and physiological roles of Aedes aegypti spermathecal-related genes.

BACKGROUND: Successful mating of female mosquitoes typically occurs once, with the male sperm being stored in the female spermatheca for every subsequent oviposition event. The female spermatheca is responsible for the maintenance, nourishment, and protection of the male sperm against damage during storage. Aedes aegypti is a major vector of arboviruses, including Yellow Fever, Dengue, Chikungunya, and Zika. Vector control is difficult due to this mosquito high reproductive capacity. RESULTS: Following comparative RNA-seq analyses of spermathecae obtained from virgin and inseminated females, eight transcripts were selected based on their putative roles in sperm maintenance and survival, including energy metabolism, chitin components, transcriptional regulation, hormonal signaling, enzymatic activity, antimicrobial activity, and ionic homeostasis. In situ RNA hybridization confirmed tissue-specific expression of the eight transcripts. Following RNA interference (RNAi), observed outcomes varied between targeted transcripts, affecting mosquito survival, egg morphology, fecundity, and sperm motility within the spermathecae. CONCLUSIONS: This study identified spermatheca-specific transcripts associated with sperm storage in Ae. aegypti. Using RNAi we characterized the role of eight spermathecal transcripts on various aspects of female fecundity and offspring survival. RNAi-induced knockdown of transcript AeSigP-66,427, coding for a Na+/Ca2+ protein exchanger, specifically interfered with egg production and reduced sperm motility. Our results bring new insights into the molecular basis of sperm storage and identify potential targets for Ae. aegypti control.

Aedes aegypti larvae treated with spinosad produce adults with damaged midgut and reduced fecundity.

The mosquito Aedes aegypti is the main vector of Dengue, Chikungunya, Zika, and yellow fever viruses, which are responsible for high human morbidity and mortality. The fight against these pathogens is mainly based on the control of the insect vector with the use of insecticides. Among insecticides, spinosad bioinsecticide is efficient against A. aegypti larvae and may be an alternative for vector control. Here, we investigate the sublethal effects of spinosad during midgut metamorphosis of A. aegypti females and its cumulative effects on blood acquisition capacity and fecundity in adults. We studied the midgut because it is an important model organ directly related to blood acquisition and digestion. Treatment of larvae with spinosad induced oxidative stress, apoptosis, and damage to the midgut cells at all stages of development and in adults. There was a reduction in the number of proliferating cells and the number of enteroendocrine cells in treated individuals. In addition, damage caused by spinosad led to a reduction in oviposition and egg viability of A. aegypti females. Finally, the exposure of mosquito larvae to sublethal concentrations of spinosad interfered with the development of the midgut, arresting the blood digestion and reproduction of adult females with blood digestion and reproduction difficulties.

Morphological and morphometrical assessment of spermathecae of Aedes aegypti females.

The vectorial capacity of Aedes aegypti is directly influenced by its high reproductive output. Nevertheless, females are restricted to a single mating event, sufficient to acquire enough sperm to fertilize a lifetime supply of eggs. How Ae. aegypti is able to maintain viable spermatozoa remains a mystery. Male spermatozoa are stored within either of two spermathecae that in Ae. aegypti consist of one large and two smaller organs each. In addition, each organ is divided into reservoir, duct and glandular portions. Many aspects of the morphology of the spermatheca in virgin and inseminated Ae. aegypti were investigated here using a combination of light, confocal, electron and scanning microscopes, as well as histochemistry. The abundance of mitochondria and microvilli in spermathecal gland cells is suggestive of a secretory role and results obtained from periodic acid Schiff assays of cell apexes and lumens indicate that gland cells produce and secrete neutral polysaccharides probably related to maintenance of spermatozoa. These new data contribute to our understanding of gamete maintenance in the spermathecae of Ae. aegypti and to an improved general understanding of mosquito reproductive biology.

Morphological and morphometrical assessment of spermathecae of Aedes aegypti females

The vectorial capacity of Aedes aegypti is directly influenced by its high reproductive output. Nevertheless, females are restricted to a single mating event, sufficient to acquire enough sperm to fertilize a lifetime supply of eggs. How Ae. aegypti is able to maintain viable spermatozoa remains a mystery. Male spermatozoa are stored within either of two spermathecae that in Ae. aegypti consist of one large and two smaller organs each. In addition, each organ is divided into reservoir, duct and glandular portions. Many aspects of the morphology of the spermatheca in virgin and inseminated Ae. aegypti were investigated here using a combination of light, confocal, electron and scanning microscopes, as well as histochemistry. The abundance of mitochondria and microvilli in spermathecal gland cells is suggestive of a secretory role and results obtained from periodic acid Schiff assays of cell apexes and lumens indicate that gland cells produce and secrete neutral polysaccharides probably related to maintenance of spermatozoa. These new data contribute to our understanding of gamete maintenance in the spermathecae of Ae. aegypti and to an improved general understanding of mosquito reproductive biology.