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Delayed development in Fischer's pygmy fruit bat, Haplonycteris fischeri, in the Philippines
1Museum of Zoology, University of Michigan, Ann Arbor 48109.
Insights
Fischer's pygmy fruit bats exhibit an 8-month embryonic development delay, the longest known in bats. This unique reproductive strategy, observed in Megachiroptera, impacts embryonic growth and gestation periods.
Area of Science:
- Reproductive biology
- Mammalogy
- Embryology
Background:
- Embryonic diapause, a delay in development, is known in some mammals.
- This phenomenon was previously unobserved in the bat suborder Megachiroptera.
Purpose of the Study:
- To investigate embryonic development in Fischer's pygmy fruit bats ( a species of Megachiroptera).
- To document the occurrence and duration of any post-implantation developmental delays.
Main Methods:
- Histological examination of reproductive tracts from female Fischer's pygmy fruit bats.
- Collection of samples over a 5-year period in the Philippines.
Main Results:
- A significant post-implantation embryonic development delay of up to 8 months was observed.
- Embryonic growth rate dramatically slowed, with minimal increase in embryoblast size during the delay.
- Gestation period was determined to be 11.5 months, the longest recorded for any bat species.
Conclusions:
- Fischer's pygmy fruit bats demonstrate a prolonged embryonic diapause, a novel finding for Megachiroptera.
- This extended delay influences reproductive timing and contributes to the exceptionally long gestation period in this species.
Abstract:
A long delay in post-implantation embryonic development was detected in Fischer's pygmy fruit bats (palaeotropical fruit bats of the suborder Megachiroptera), the first time such a delay has been demonstrated outside the bat suborder Microchiroptera. Samples of bats were obtained from the Philippines over 5 years, and reproductive tracts were preserved and examined using standard histological techniques. Most parous female pygmy bats were impregnated in June, within a few weeks of parturition, and the embryos underwent superficial implantation at the anterior end of the uterus contralateral to the previously gravid uterus. Shortly thereafter, the rate of embryonic growth slowed tremendously for up to 8 months. During the period of delay, the mean length of the embryoblast increased only from 280 microns to 520 microns. In March of the following year, the developmental rate increased, and the embryos completed development in the next 3 months. The 8-month delay gives these bats a gestation period of 11.5 months, the longest known in bats. Most nulliparous females become pregnant at an age of 3-5 months, and their embryos entered a similar delay that terminated in March or April, after 2-6 months of delay. Males showed signs of fertility throughout the entire year, but testis volume was highest during May, June and July, at about the time when most females become receptive.