Ovarian morphology and folliculogenesis and ovulation process in the flat‐faced fruit‐eating bat Artibeus planirostris and the Argentine brown bat Eptesicus furinalis: A comparative analysis

Abstract

The Neotropical bat species Artibeus planirostris and Eptesicus furinalis present a different morphology of the female reproductive organs: the first presents a simplex uterus, while the second presents a bicornuate uterus, but there is no information about their ovaries. Our aim was to compare the general ovary morphology and the folliculogenesis process in these species to increase the knowledge about the reproductive diversity of tropical bats. We observed a morphological distinction between the ovaries of both species: A. planirostris presents the primordial follicles located in a cranial portion of the ovary and the interstitial gland cells are not distinctive, while in E. furinalis, the primordial follicles are located throughout the cortex, and there is an abundance of interstitial gland cells. Both species present binovular or triovular follicles. Artibeus planirostris is a monovular species, with a preferential ovulation in the left side. Some females of E. furinalis exhibited two corpora lutea in the same ovary, and others presented a corpus luteum in both right and left ovaries at the same time; thus, E. furinalis is a polyovular species. Our results express the variation between two Neotropical species, reflecting the great variation in the reproductive aspects in Chiroptera.

Morphology of the Ovaries, Uterine Tubes and Uterus ofPteronotus gymnonotus(Chiroptera: Mormoopidae)

“…In the ovaries that presented corpus luteum, there was a greater thickening of the endometrial layer of this same animal, showing an increase in the number of glands, indicating the end of the ovulation phase and the beginning of the luteal phase of the ovarian cycle. However, ovaries that did not present a corpus luteum, but with follicles in growth and development, were associated with a thinner endometrium and a reduction of the glands, indicating a proliferative phase of the endometrial cycle; which was in line with observations made in ovaries with and without corpus luteum, along with variations in the thickness of the endometrium in the uterus (Bueno, 2019).…”

“…This gland is composed of functional cells for the synthesis of progesterone, the main regulator of the pituitary secretion of gonadotropins necessary for the maintenance of the corpus luteum until the initial pregnancy (Bueno, 2019). If it does not occur, the corpus luteum regresses and begins its degeneration process, and is now called the hemorrhagic corpus luteum (Bueno, 2019). As its regression advances, a scar tissue called corpus albicans begins to form (Beguelini et al, 2013), culminating in a decrease in the production of estrogen and progesterone by the corpus luteum, which contributes to the elimination of the functional layer.…”

“…This gland is composed of functional cells for the synthesis of progesterone, the main regulator of the pituitary secretion of gonadotropins necessary for the maintenance of the corpus luteum until the initial pregnancy (Bueno, 2019). If it does not occur, the corpus luteum regresses and begins its degeneration process, and is now called the hemorrhagic corpus luteum (Bueno, 2019).…”

“…They are composed of four basic layers: the serous layer, formed by connective tissue and mesothelium; a muscle layer formed of smooth muscle arranged in an inner circular layer and an outer longitudinal layer; and the mucosa formed by the epithelium and a lamina propria of loose connective tissue (Beguelini et al, 2020). The epithelium is usually simple and varies from cubic to columnar (Beguelini et al, 2013), where it is composed of two cell types, secretory and ciliated cells, but in the vast majority, secretory cells are rare, and the epithelium is formed mainly, by hair cells that move towards the uterus, taking in that direction the mucus that covers its surface, produced by the secretory cells that are interposed between the hair cells (Bueno, 2019; Beguelini et al, 2020).…”

A review of the breeding biology of Chiroptera

“…Like in studies of reproductive anatomy, fewer studies of gamete morphophysiology were focused on females than on males. Research on females was focused on ovarian morphology and the folliculogenesis process (Komar et al 2007, Álvarez et al 2014, Bueno et al 2019, as well as on investigating the effects of resistin on ovarian folliculogenesis and on identifying ovarian protein profiles and correlating their expression with adiposity-induced changes in ovarian activity leading to the suppression of ovulation (delayed ovulation; Singh et al 2014Singh et al , 2015.…”