Eggs of the tropical species A. (Oc.) epactius reared under SD were wider than those reared under LD. Electron microscopy studies of eggs of the close temperate species A. (Oc.) atropalpus able of diapause revealed different and stronger modifications in size and shape: LD eggs were longer and narrower than SD eggs, with changes

in the outer chorion structure ( Linley and Craig, 1994). However no differentiation of the possible factors, day length and diapause, responsible for these changes was obtained. Our study is thus the first to demonstrate that maternal photoperiod, and not diapause, influences egg volume in an Aedes species capable of diapause. The structure of Natural Product Library mosquito eggs is therefore sensitive to several seasonal factors. Indeed, Anopheles sacharovi (Favre) and Anophelespunctipennis (Say) produce “winter” eggs almost totally covered by exochorion ( Theodor, 1925 and Fritz and Washino, 1992), and “winter” eggs of A. sacharovi possess a small float and are larger than “summer” float-less eggs. In these cases, the morphological differentiation originates in response

to temperature fluctuations, and not from the diapause syndrome, as diapause occurs at the larval or adult stages in Anopheles species ( Theodor, 1925). The latter are capable of egg quiescence, a process fairly similar to diapause at the molecular level ( Poelchau et al., 2013b), however quiescence is selleck by definition an aseasonal state of inactivity ( Vinogradova, 2007). The mechanisms involved in Selleckchem Staurosporine egg structure variability in mosquito are not determined and may be

multiple. Concerning the photoperiodic causality, we suspect that a circadian rhythm plays a part in the hormonal production and reserve storage, such as was demonstrated in several insect groups, including mosquitoes (Bloch et al., 2013). Egg production is regulated by hormones which are photophase dependent, as demonstrated in Hemiptera Rhodnius prolixus ( Vafopoulou et al., 2012). Lipids represent the major energetic source of eggs and are essential for the development of the embryo. Lipid reserve in eggs is provided by the mother ( Ziegler and Van Antwerpen, 2006). If that storage is dependent of photoperiod, and is more particularly developed during scotophase, long nights will enhance egg volume. Organism size cannot be explained by the simple sum of mechanisms that regulate the size and number of cells in organs ( Nijhout, 2003), but a positive relationship exists with the energy stock and egg size in some species, like the butterfly Bicyclus anynana ( Geister et al., 2009). A study carried out on a US temperate strain of A. albopictus found a lipid reserve more important by 30% in diapause-induced pharate larvae ( Reynolds et al., 2012), linked to an increase in egg volume.