This issue of the journal is publishing a relatively short and unassuming, but “landmark”, article by Roy and Krishna, showing that sperm storage in the female reproductive tract of the Greater Asiatic Yellow House Bat, Scotophilus heathii, is mediated via the action of androgens. This manuscript is the latest in a long-running search by these and other researchers to find an explanation for the unusually effective mechanism of sperm storage in the female reproductive tract. Like a number of other bat species (Racey, 1975, 1979), these animals mate in the autumn but delay fertilisation for about 5 months until the following spring (Gopalakrishna and Madhavan, 1978). The spermatozoa clearly remain viable and fertile within the female reproductive tract, and detailed histological and ultrastructural studies have shown that the spermatozoa become intimately associated with the surface of the uterine and oviductal epithelium (Racey et al., 1973, 1987) (Fig. 1). Bat spermatozoa in close relationship, with indentations (I) and/or the flat membrane of non-ciliated epithelial cells (Nc) in the intra-mural part of the utero-tubal junction. The spermatozoa are surrounded also by cilia (C) of ciliated epithelial cells (Cc). G, granule; K, kinetosome (reprinted with permission from Racey et al., 1987). The intimate association between spermatozoa and female reproductive epithelial cells is a feature of sperm storage in many different species, and has consequently been widely interpreted as showing that the epithelial cells are providing the spermatozoa with nutrients. However, current concepts in sperm biology are not really compatible with the view that spermatozoa require “nourishment” to survive, and a more contemporary view might include the thought that cell–cell interactions are involved in signalling pathways that can control physiological responses. In other words, the female reproductive tract might be “switching-off” the spermatozoa by an unknown mechanism. Unfortunately, careful morphological observations alone have not, so far, proved sufficiently informative to explain how sperm survival in female bats is achieved, when other mammalian species are only able to maintain sperm viability for a maximum of a few days. In fact, it is galling for a gamete biologist to realise that effective sperm storage in the female reproductive tract is so widespread in nature as to be almost commonplace (Howarth, 1974; Holt and Lloyd, 2010). Some amphibians and many birds have evolved the capacity to store spermatozoa for several weeks or months, while some fish and reptiles are able to store viable spermatozoa for more than a year. The adaptive explanation for such successful sperm storage is that there are benefits gained by reducing the need for temporal synchronisation between copulation and ovulation (Birkhead and Møller, 1993). Evolutionary studies have shown that the ability to promote sperm survival has evolved independently in the different taxonomic groups, a finding that provokes the thought that either the secret of prolonged sperm survival in vivo is really simple and should therefore be trivial to develop or, alternatively, that there must be an array of possible solutions to the problem of keeping sperm alive for long periods. Either way, reproductive physiologists have to be somewhat embarrassed that the mechanisms have so far eluded them. The interesting advance that Roy and Krishna has made is to show that in the case of S. heathii, sperm storage is dependent upon the maintenance of high circulating androgen concentrations. Although these authors have previously reported that delayed ovulation in this species is accompanied by the production of androgens in the ovaries (Abhilasha and Krishna, 1996; Singh and Krishna, 1996), they had not apparently made the connection with sperm storage until recently, when they showed that androgen receptors are present within the oviductal epithelium (Roy and Krishna, 2010), together with androgen binding protein. In their article, they suggested that androgens might be exerting local effects on spermatozoa via non-genomic mechanisms, with the androgen binding protein providing a convenient means of elevating the androgen concentrations at the appropriate site(s) for sperm storage. The latest article supports the androgen-based hypothesis by showing that when a female bat is treated with the anti-androgen, flutamide, the ability to sequester and store spermatozoa is lost. However, Roy and Krishna have also shown that during sperm storage the utero-tubal junction expresses B-cell lymphoma factor 2 (Bcl-2), which, together with a family of related cytoplasmic proteins, are key regulators of apoptosis (for reviews, see Chipuk et al., 2010; Llambi and Green, 2011). In the context of sperm storage mechanisms, Roy and Krishna hypothesise that the Bcl-2 is acting as a survival factor with anti-apoptotic activity, and support their view by showing that Bcl-2 expression is testosterone-dependent. They also showed that the utero-tubal junction expresses caspase 3, a pro-apoptotic factor (Degterev et al., 2003) and observed some degree of modulation of gene expression in relation to the sperm storage events. This interplay between pro- and anti-apoptotic factors is of considerable interest because they suggest a plausible mechanism for the control of sperm viability. It is not clear from the current evidence whether these factors act primarily to modulate the function of the epithelial cells and/or they affect the spermatozoa themselves. Apoptosis in somatic cells involves the control of gene expression, and the eventual controlled degradation of nuclear DNA, but these principles cannot immediately be transposed to spermatozoa, which lack some of the requisite mechanisms. However, it is plausible to suppose that a subset of apoptotic processes, involving changes in membrane lipid architecture and sperm DNA fragmentation, could occur in vivo. By coincidence of timing, Urhausen et al. (2011) recently described the expression of caspase 3 in the dog oviduct with respect to the estrous cycle, and suggested that the control of apoptosis could be a functional component of sperm storage mechanisms prior to fertilisation. The dog is a particularly relevant mammalian species in the context of sperm storage because the unusual post-ovulatory oocyte maturation process requires that sperm viability is maintained for several days within the oviduct before fertilization (Doak et al., 1967).2 An engulfed bat spermatozoon (Es) within a non-ciliated epithelial cell (Nc) in the intramural part of the utero-tubal junction. N, nucleus (reprinted with permission from Racey et al., 1987). These new findings about sperm storage in a bat species represent the first really significant advance for several decades in our understanding of the mechanisms behind adaptive sperm storage. Although the observations have been drawn from a single species of bat, the direct linkage with apoptosis and its regulation make me cautiously optimistic that various forms of this mechanism could be widely distributed across different taxonomic groups. This would seem to represent a rich seam for future academic research in this area, but it may also generate practical outcomes such as the ability to develop successful long-term, but non-cryogenic, sperm storage methods for use in reproductive technologies.