Relationship between delayed embryonic development and metabolic factors and fat deposition in fruit bat Cynopterus sphinx
Arnab Banerjee A , K.J. Meenakumari A and Amitabh Krishna A BA Department of Zoology, Banaras Hindu University, Varanasi, 221 005, India.
B Corresponding author. Email: akrishna_ak@yahoo.co.in
Reproduction, Fertility and Development 19(5) 626-633 https://doi.org/10.1071/RD06160
Submitted: 7 December 2006 Accepted: 16 April 2007 Published: 31 May 2007
Abstract
The present study was undertaken in the fruit bat Cynopterus sphinx, which breeds twice in quick succession at Varanasi, India. Its gestation period varies significantly in the two successive pregnancies of the year owing to delayed embryonic development during the first (winter) pregnancy. The primary aim of the present study was to determine the role of metabolic factors in delayed embryonic development in the fruit bat C. sphinx. Variation in bodyweight, fat deposition, oxygen (O2) consumption rate, basal metabolic rate (BMR), body temperature (Tb) and hepatic succinate dehydrogenase (SDH) activity, along with circulating levels of thyroid hormones (tri-iodothyronine and thyroxine), were examined as metabolic factors during the two successive pregnancies in C. sphinx. The increase in bodyweight observed in November was due to accumulation of white adipose tissue in the posterior abdominal region. A significant decline in O2 consumption rate, BMR, Tb and SDH activity was found in early winter in November–December, which coincides closely with the period of fat accumulation and with the period of delayed embryonic development in C. sphinx. A significantly higher O2 consumption rate, BMR, Tb and SDH activity was noted during the second pregnancy in, when embryonic development was relatively faster. Thyroid hormone levels were high during the period of embryonic delay compared with levels during the remaining months. The results of the present study suggest that the delayed embryonic development in C. sphinx during early winter may be due to a low O2 consumption rate, BMR, Tb and SDH activity in November–December. The energy saved by suppressing embryonic development in this species may be advantageous for fat accumulation. Increased thyroid hormone levels during the early winter period might facilitate fat accumulation in C. sphinx.
Additional keywords: basal metabolic rate, body temperature, O2 consumption, succinate dehydrogenase.
Acknowledgements
This study was supported by grants to AK from The Department of Science and Technology, New Delhi.
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