Abstract
Anatomy of bat genital organs has been conventionally studied by gross and microscopic observations to date. Here, we employ both histological observation and diceCT (diffusible iodine-based contrast-enhanced computed tomography) to study the detailed three-dimensional morphological structure of the male genital organs in bats, using the greater horseshoe bat, Rhinolophus ferrumequinum. This is the first study to three-dimensionally describe the whole reproductive organs of bats in detail. Our highly resolved three-dimensional reconstruction reveals that the male organs of R. ferrumequinum consist of paired testes, epididymides, deferent ducts, and five accessory genital glands. The boundary between the ampullary and vesicular glands has been difficult to identify in previous observations, but our diceCT imaging allowed us to clearly differentiate the two. We found that the ampullary gland is located at the terminal part of the deferent ducts, and the vesicular gland lies distal to the ampullary glands. This species possesses a single and carrot-shaped urethral gland, which is not found in most chiropteran families. The presence of the urethral gland in this species and its secretions suggest that after copulation this species is capable of forming a vaginal plug, which can seal the female’s vaginal orifice to block the entrance of spermatozoa from other males. The presence of the urethral gland and elongated epididymal tail and the fact that some individuals can terminate their hibernation and reactivate imply forced copulation on hibernating females can occur in R. ferrumequinum.
Highlights
There are approximately 1300 species of bats (Order Chiroptera) distributed worldwide, from tropical regions to temperate regions (Wilson and Mittermeier 2019)
We confirmed that the male genital organs of R. ferrumequinum comprise five accessory genital glands, paired testes, epididymides, and deferent ducts (Fig. 1)
We found that the male genital organs of R. ferrumequinum are composed of the paired testes, epididymides, deferent ducts, and accessory genital glands, consistent with the cases reported for R. hipposideros (Gaisler 1966) and R. megaphyllus (Krutzsch et al 1992)
Summary
There are approximately 1300 species of bats (Order Chiroptera) distributed worldwide, from tropical regions to temperate regions (Wilson and Mittermeier 2019). Bats had been traditionally classified into two suborders, Megachiroptera and Microchiroptera, based on morphological traits (Dobson 1875; Smith 1976; Jones et al 2002). Molecular genetic studies in recent decades have shown that Microchiroptera bats are not monophyletic and that members of the Rhinolophoidea superfamily (previously classified as Microchiroptera) are the sister group of Pteropodidae (Jones and Teeling 2006). The classification has been largely revised as Yinpterochiroptera (for Rhinolophoidea + Megachiroptera) and Yangochiroptera (for non-rhinolophoid microchiropterans)(Springer 2013). Bats have high interspecific variation in their reproductive strategies and variable genital morphology, which reflects the ecological diversity. The mammalian male reproductive organs comprise paired testes, epididymis, and accessory genital glands, with the testis, epididymis, and accessory genital glands exhibiting
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