Histological Description of Gonadal Development in a Neotropical Insectivorous Bat Eumops patagonicus (Chiroptera: Molossidae).

The order Chiroptera is one of the most diverse orders in terms of the number of species; however, very few studies have been conducted in this group regarding its embryonic development. In this area, studies have focused on staging through morphological characters, but those describing organogenesis are scarce. Therefore, this work describes the gonadogenesis of Eumops patagonicus, a Sudamerican insectivorous bat, with an emphasis on ovarian development and determination of the migration stage of the primordial germ cells (PGCs) through immunostaining. Pregnant females of this species were captured to carry out the study, and the embryos were processed to obtain histological sections using the conventional histology technique and immunohistochemistry (OCT4, PCNA, Bax and Bcl-XL). Critical stages of gonadal differentiation were described, starting from the formation of the urogenital ridge and the identification of PGCs with the positive reaction for OCT4 in embryological development stage 13. At stage 17 of development, an undifferentiated gonad with active proliferation is observed and then a defined testis (S. 21) and ovaries (S.23 and S.25). The embryo ovaries S. 23 show a cortex formed for ovogonia cysts/nets that have a craniocaudal development with differences in the immunolabelling of PCNA, Bax and Bcl-XL. The embryo ovaries S. 25 show the primordial follicles in the ovary cortex. The results determined that there is a conserved pattern in embryonic development in this order when comparing E. patagonicus with frugivorous bats. This information is important for the establishment of relations in development in mammals and within the order Chiroptera.