Embryonic Development of the Egyptian Fruit Bat Rousettus aegyptiacus (Mammalia: Chiroptera: Pteropodidae)

Bats have evolved several unique morphological traits related to powered flight, such as wings, patagia, minute hindlimbs, large pinna, and a larynx specialised for echolocation. Studies of embryonic development in bats provide important insights into the mechanisms underlying the evolution of flight-related structures in vertebrates. Although embryonic development has been described in some bats species, only one species of Old World fruit bats (family Pteropodidae) has previously had its embryonic development examined. In this paper, we describe the embryonic development of the Egyptian fruit bat, Rousettus aegyptiacus, ranging from middle pharyngula to just before birth. We compared the growth patterns during embryogenesis among nine bat species for which data on embryonic development have been obtained. We discovered that i) the crown-rump length (CRL) is almost equivalent among the bat species until stage 22, and ii) compared to other bat species examined, the growth rate rapidly and substantially increases in two pteropodid species (R. aegyptiacus and R. amplexicaudatus) after stage 22. In placental mammals, larger body size at birth is advantageous for postnatal survival. To obtain large adult body size, some pteropodid bats may accelerate their postnatal growth and take advantage of larger body size at birth.