Female reproductive patterns in nonhibernating bats

Abstract

The major reproductive events in the oestrous cycles of nonhibernating mega- and microchiropteran species are reviewed. However, special attention is given to the reproductive biology of the temperate North American species, Tadarida brasiliensis mexicana (Molossidae), the Mexican free-tailed bat, which expresses dextral uterine and ovarian dominance. Only the larger right ovary is capable of producing an ovulatory follicle and the left has long been considered atrophic. In order to elucidate the normal oestrous cycle and define the structural and functional characteristics of the ovaries of this nonhibernating bat several analytical technique were utilized. These included light microscopic analysis, histochemical localization of delta 5-3 beta-hydroxysteroid dehydrogenase (HSD) activity, and radioimmunoassay of seasonal plasma progesterone levels. Interstitial tissue was found in both ovaries, but the left was almost entirely an interstitial organ. Histochemical analysis demonstrated that the gonads have seasonally varying amounts of delta 5-2 beta-HSD localized either in the thecal cells of the Graafian follicle or in the interstitium. The corpus luteum persisted throughout gestation, reaching maximum development just prior to parturition. Circulating progesterone levels correlated directly with luteal gland size and peaked at 106 ng/ml when the corpus luteum was largest.

Changes in progesterone concentrations in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus

“…The baseline level (7 ng/ml) of plasma progesterone in the Japanese long-fingered bat during a period when no luteal tissue was present was similar to that (~5 ng/ml) reported for the pallid bat (Oxberry, 1979) and the Mexican free-tailed bat (Jerrett, 1979), but the baseline values in the California leaf-nosed bat appear as 'zero' (Burns & Easley, 1977). Relatively high baseline values of plasma progesterone observed during non-pregnancy in the former 3 bat species suggest that the measured progesterone is secreted by the ovarian interstitial gland tisue as suggested for the Mexican free-tailed bat (Jerrett, 1979) and/or by the adrenal cortex as in the ewe (McCracken & Baird, 1969) and women (Baird, 1976).…”

“…Relatively high baseline values of plasma progesterone observed during non-pregnancy in the former 3 bat species suggest that the measured progesterone is secreted by the ovarian interstitial gland tisue as suggested for the Mexican free-tailed bat (Jerrett, 1979) and/or by the adrenal cortex as in the ewe (McCracken & Baird, 1969) and women (Baird, 1976). On the other hand, ACTH stimulation can increase plasma progesterone values 350-500% over baseline levels in post-menopausal women (Vermeulen, 1976).…”

“…In non-hibernating bat such as the Mexican free-tailed bat, Tadarida brasiliensis mexicana (Jerrett, 1979), which exhibited no delayed implantation and development, plasma progesterone concen¬ trations increase steadily until the mid-point of pregnancy and then decline after parturition. On the other hand, in hibernating bats such as the pallid bat, Antrozous pallidus (Oxberry, 1979), and pipistrelle bat, Pipistrellus pipistrellus (Racey & Swift, 1981), the progesterone concentrations fluc¬ tuate until the time of a peak of progesterone just before parturition; nevertheless the progesterone concentrations during pregnancy in the 2 species do not fall to the values at the beginning of gestation and/or the baseline value.…”

Birth synchrony in greater spear‐nosed bats (Phyllostomus hastatus)

“…The rate of embryonic development can change depending upon temperature and maternal nutrition in temperate-zone bats (Racey & Swift, 1981;Bernard, 1994;Racey & Entwistle, 2000). In the tropics as well as in temperate and subtropical zones, some bats demonstrate an obligate post-implantation delay in embryonic growth, including at least four phyllostomid bats: the short-tailed fruit bat, the Jamaican fruit bat Artibeus jamaicensis, the Mexican big-eared bat Macrotus waterhousii and the California leaf-nosed bat M. californicus (Jerrett, 1979;Racey, 1982;Rasweiler & Badwaik, 1997;Racey & Entwistle, 2000). James (1977) killed adult female greater spear-nosed bats at various reproductive stages, both pre-and postconception, and did not ®nd evidence of sperm storage or any delay in implantation or gestation.…”

Dinámica poblacional, selección de sitios de percha y patrones reproductivos de algunos murciélagos cavernícolas en el oeste de México

“…En las regiones tropicales se han descrito cuatro patrones reproductivos generales para los murciélagos: monoestría estacional, poliestría bimodal estacional, poliestría estacional y poliestría no estacional (Jerret 1979, Singh & Krishna 1997. Se sabe que en los trópicos la precipitación es la variable climáti-ca más influyente en sus ciclos reproductivos, actuando directamente como una señal externa que indica el inicio de la actividad reproductiva o indirectamente por su efecto en la fenología de las plantas e insectos de los que se alimentan (Racey 1982, Cumming & Bernard 1997, Racey & Entwistle 2000.…”