Normal embryonic development of the Japanese pipistrelle, Pipistrellus abramus

The normal embryonic development of the Japanese pipistrelle, Pipistrellus abramus was described. A total of 13 stages between the early pharyngula and the embryo just before birth were established, based on external morphological features of 33 embryonic specimens. To aid embryological comparison between chiropteran lineages, the stage numbers used in the Carollia perspicillata embryonic staging system (Cretekos et al., 2005) were applied to each embryonic stage of P. abramus. The size (crown-rump length, CRL) of P. abramus embryos became larger throughout ontogeny at a relatively constant rate. When the CRL of embryos was compared in each morphologically corresponding embryonic stage, the CRL of P. abramus was always smaller than that of C. perspicillata. The overall nature of organogenesis was almost similar in both P. abramus and C. perspicillata. Species-specific differences in bats were observed at later stages of embryogenesis, notably in the craniofacial and tail regions.