Effect of aging on the photic entrainment in the frugivorous bat, Rousettus leschenaulti

Abstract

Aging disrupted the photic entrainment in old (∼15 years) frugivorous Rousettus leschenaulti bats as natural light – dark (LD) cycles in the field or artificial LD cycles of 12 h of light at 2000 lux and 12 h of complete darkness failed to entrain them (Vanlalnghaka & Joshi 2005; Vanlalnghaka et al. 2005). The results were attributed to the age-related decline in photic sensitivity and/or the period of zeitgeber (T) deviating too much from the free-running period (τ) of bats. In the present study, the old bats were subjected to LD cycles in which the intensity of the photophase was raised to 6000 lux and Ts of 23.2 h and 24.9 h were exactly that of τ in the scotophase of LD cycles and in constant darkness, respectively. These LD cycles also failed to entrain the old bats which unambiguously demonstrates that aging in R. leschenaulti disrupted the integrity of the photic entrainment mechanism.

Keywords:

• Aging
• bat
• circadian rhythm
• Rousettus leschenaulti

Acknowledgments

These studies are supported by the Research Grant No. 14/14/2000-ERS/RE funded by the Ministry of Environment and Forest, New Delhi to DSJ. The experiments comply with the “Principles of animal care.” No. 86 – 23, NIH, 1986.