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Journal of Biological Rhythms, Vol. 10, No. 4, 319-323 (1995)
DOI: 10.1177/074873049501000405

Circadian Aspect of Photoperiodic Time Measurement in a Female House Sparrow, Passer domesticus

G. Ravikumar

Tasar Research and Training Institute, Central Silk Board, Nagri, Ranchi - 835 303, India

B. Senthilkumaran

Department of Zoology, Banaras Hindu University, Varanasi - 221 005, India

P.D. Tewary

Department of Zoology, Banaras Hindu University, Varanasi - 221 005, India

A.K. Goel

Tasar Research and Training Institute, Central Silk Board, Nagri, Ranchi - 835 303, India

Endogenous circadian rhythms are involved in various photoperiodic responses of birds. Investigations involving the mechanisms of photoperiodic time measurement in birds have been confined mainly to temperate zone species using males exclusively. Due to the paucity of experimental evidence on sub tropical birds that have very wide distribution, the present study was performed using subtropical female house sparrows. Photoperiodic sparrows were sub jected to various T cycles for 60 days in which a fixed 3-h photophase was combined with scotophase in cycles of 20-30 h duration. Simultaneously, two groups of birds were also exposed to short days (light:dark = 8L:16D) or long days (15L:9D) as controls. Significant ovarian growth was found only in cycles of 3L:17D, 3L:23D, 3L:25D, and 3L:27D as well as in 15L:9D, whereas no positive response was detected in 3L:19D, 3L:21D, and 8L:16D. Plasma levels of estradiol showed a close relation to ovarian growth. The results indicate that photoperio dic time measurement in house sparrows involves an endogenous circadian rhythm.

Key Words: photoperiodism • I cycles • circadian rhythm • house sparrows


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