Spontaneous decidual reactions and menstruation in the black mastiff bat, Molossus ater

Abstract

Uterine function was assessed histologically in nonpregnant Molossus ater removed from a laboratory breeding colony. During the luteal phase of the cycle, bilateral decidual reactions were found to develop spontaneously in the absence of either embryos or experimental manipulation of the uterus. These included the formation of early decidual giant cells, closure of the uterine lumina, and morphological changes in the endometrial blood vessels. Some endothelial cell hypertrophy was noted in much of the decidua, but this was most pronounced in vessels associated with an unusual vascular tuft that formed in the endometrium surrounding the cranial end of the uterine lumen. These latter vessels also developed very prominent basal laminae. In pregnant bats, this tuft played a central role in the morphogenesis of the definitive discoidal chorioallantoic placenta. At the end of nonpregnant cycles, the decidua became necrotic and was sloughed off with associated bleeding. As in menstruating catarrhine primates, the endometrium of M. ater is vascularized by spiral arterioles and populated by distinctive granulocytes containing large, acidophilic granules. Increased coiling of these arterioles did not appear to be an essential element in the mechanism of mensturation in this species. M. ater is a monotocous, seasonal breeder, with a relatively long gestation period. Although it has a bicornuate uterus, ovulation and implantation appear to occur only on the right side of the tract. The ability to menstruate probably affords this bat an efficient mechanism for eliminating a highly differentiated endometrium from the usual implantation site in the event of a reproductive failure. In the wild, this may provide M. ater with another chance to establish a pregnancy at a still opportune time during the same breeding season.

Neutrophil depletion retards endometrial repair in a mouse model

“…In women, menstruation is a unique form of tissue breakdown that occurs with each reproductive cycle and is followed by extremely rapid repair of the tissue without scarring (Salamonsen 2003). These events do not occur in other species with oestrous cycles, except to a limited extent in some old world primates (Finn 1987) and in a small number of bats (Rasweiler 1991;Rasweiler and de Bonilla 1992). One reason for this might be that, in women, decidualisation of the endometrial stroma occurs naturally during the late secretory phase of the cycle in preparation for implantation, whereas decidualisation only takes place in the presence of a blastocyst in other species with haemochorial placentation.…”

Embryonic Staging System for the Black Mastiff Bat, Molossus rufus (Molossidae), Correlated With Structure‐Function Relationships in the Adult

“…The reproductive biology of M. rufus has also been extensively studied under controlled conditions in captivity (Rasweiler, 1987, 1988, 1990a, b, 1991a, b, 1992, 1993; Badwaik et al, 1998), revealing this species to be an interesting model for studies of the biology of menstruation, trophoblastic growth and differentiation, and placental morphogenesis. During its menstrual cycle, M. rufus also exhibits, within its uterus, the most pronounced example of physiological (nonpathological) angiogenesis thus far observed in any adult mammal (Rasweiler, 1991a). Our description of the postimplantation embryology in M. rufus further advances the utility of this bat species for developmental studies.…”

Embryonic Staging System for the Black Mastiff Bat,Molossus rufus(Molossidae), Correlated With Structure‐Function Relationships in the Adult

“…The reproductive biology of M. rufus has also been extensively studied under controlled conditions in captivity (Rasweiler, 1987(Rasweiler, , 1988(Rasweiler, , 1990a(Rasweiler, ,b, 1991a(Rasweiler, ,b, 1992(Rasweiler, , 1993Badwaik et al, 1998), revealing this species to be an interesting model for studies of the biology of menstruation, trophoblastic growth and differentiation, and placental morphogenesis. During its menstrual cycle, M. rufus also exhibits, within its uterus, the most pronounced example of physiological (nonpathological) angiogenesis thus far observed in any adult mammal (Rasweiler, 1991a). Our description of the postimplantation embryology in M. rufus further advances the utility of this bat species for developmental studies.…”

“…These studies also revealed that the species is a spontaneous ovulator with a functional luteal phase to its cycle. The cycle is terminated by true menstruation (Rasweiler, 1988(Rasweiler, , 1991a.…”