Detailed reproductive pattern and associated endocrine characteristics have been documented in only a few species of order Chiroptera. The aim of the present study was to examine the changes in
body weight, serum
insulin,
leptin,
androstenedione and
luteinizing hormone (LH) concentrations during annual ovarian cycle in the sheath-tailed bat, Taphozous longimanus. Bats were sampled over three years.
Leptin, a satiety
hormone produced primarily by adipose tissue, provides information to feeding center of the brain about nutritional status, fat mass, appetite and energy expenditure. The circulating concentration of
leptin begins to increase from October and attains a peak in December. The peak serum
leptin concentration coincides with
body weight in November before winter dormancy in December. The serum
leptin levels dissociate from
body weight during December. The other peaks of serum
leptin levels coincide with late stages of the two successive pregnancies. The serum
insulin concentration begins to increase from September and attains a peak during December. The
insulin concentration remains low from January to August. The circulating
androstenedione concentration begins to increase in October, reaching a peak in December. This increase in
androstenedione concentration correlated with the period of heavy accumulation of abdominal fat and increase in
body weight. There was a sharp decline in
androstenedione concentration and
body weight in January. The serum LH shows peaks, in November, coinciding with the peaked
body weight, the other peaks in January and May, coinciding with ovulation for the two successive pregnancies. The high
leptin and
insulin levels might be responsible for the maintenance of reproductive response and gonadal function during adverse environmental condition in the winter, while high
androstenedione, and associated
body weight along with LH might be responsible for maintaining basal gonadal function. We conclude that high
leptin,
androstenedione and
insulin serve, as signal for the reproductive functions in that sufficient body fat are available to meet the caloric demands and maintain normal function during adverse winter conditions.