Aedes aegypti is the most important vector of dengue and urban yellow fever viruses, due in some measure to the high reproductive output of Ae. aegypti

Aedes aegypti is the most important vector of dengue and urban yellow fever viruses, due in some measure to the high reproductive output of Ae. aegypti females. In spite of such high output, Ae. aegypti females are restricted to a single mating event, sufficient to acquire enough sperm to fertilize a lifetime supply of eggs (Rogers et al. 2008). How mosquito females are capable of maintaining live gametes for several days or weeks remains unknown. Following copulation, insect spermatozoa are housed within the sac-like reservoir formed by the distal and dilated portion of the spermatheca. The reservoir is connected to the bursa copulatrix through spermathecal duct that allows passage of male gametes from the bursa copulatrix to the reservoir following mating or in the opposite direction for egg fertilization. A spermathecal pump, also known as sphincter, is located at the site of attachment of the spermathecal duct to the reservoir. The spermathecal pump of bees and ants is formed by several muscular fibres arranged in different orientations (Martins & Serrão 2002, Gobin et al. 2006) and functions to prevent gametes from escaping from the reservoir and to control their release during egg fertilization by contracting and relaxing, respectively (Gerber & Klostermeyer 1970). The glandular portion of the spermatheca generally consists of clustered cells located just above the reservoir and/or the duct epithelia. Depending on the insect species, the clustered cells have either individual ducts that transport secreted substances directly into the reservoir (Curtin & Jones 1961) or a common glandular duct (Lawson & Thomas 1970, Martins et al. 2008). Secreted substances are thought to include nutrients that keep the spermatozoa viable during the entire reproductive life of the adult female (Schoeters & Billen 2000, Klenk et al. 2004). In Apis mellifera, the spermatheca participates in the maturation and viability of the spermatozoa, creating a suitable environment by isolating gametes from the haemolymph and by synthesizing antioxidants (e.g. catalase, glutathione-S-transferase and superoxide dismutase) that protect gametes against reactive oxygen species (Collins et al. 2004, Kumano et al. 2009, den Boer et al. 2009). In addition, genes expressed in the spermatheca of Drosophila simulans are involved in controlling the viscosity of the internal milieu of the spermathecal lumen, as well as in sugar metabolism to provide energy sources to the gametes and in antifungal defence (Prokupek et al. 2008). The ultrastructure of the Ae. aegypti spermatheca was described previously (Christophers 1960, Clements & Potter 1967). However, morphological studies combining histology, histochemistry, confocal and scanning and transmission electron microscopes have never been done. Here, we combined histology, histochemistry and microscopy approaches to reveal general and detailed aspects of Ae. aegypti spermathecae morphology, including cell composition and nuclear size. The morphology of the spermathecae, as well as the morphometry and the number of gland cells and their cytoskeleton, do not differ between unmated to mated Ae. aegypti females, showing that just the organ filling by male gametes is Financial support: FAPEMIG, DBG/UFV TVP is an undergraduate student in the Biology program at UFV and supported by PIBIC/CNPq, GFM is supported by FAPEMIG (CBB-APQ-00394-09) and MRO is supported by NIH (AI074691, AI088051). + Corresponding author: gmartins@ufv.br Received 12 January 2012 Accepted 27 March 2012 Morphological and morphometrical assessment of spermathecae of Aedes aegypti females