Effect of environmental and physiological variables on saliva production in Hirudinaria granulosa (Indian cattle leech)

Rhythmicity in the saliva production of leech Hirudinaria granulosa has not been evaluated. This is, possibly, the first effort to evaluate the amount of saliva production under different environmental and physiological variables. A total of 90 leeches were divided into six groups (n=15) to elucidate the variation in saliva production based on temperature, body weight, and time period. Significantly (P≤0.01) higher volume of saliva was produced (2.23±0.10) at a temperature of 37 oC compared to that at 25 oC (1.53±0.11). Based on body weight, a significantly (P≤0.01) higher amount of saliva (2.52±0.05) was produced by the leeches of the large group (≥0.4g weight) as compared to the smaller group (1.66±0.08) with a bodyweight of (≤0.3g weight). In addition, the Pre-feeding and post feeding body weight of leeches (n=30) with saliva production revealed significantly high correlation of 0.962 and 0.870. Evaluation based on periodicity revealed a significantly higher amount of saliva production in the morning hours (2.32 ±0.09) compared to evening hours (2.01±0.10). Thus, our study concluded a relatively more elevated amount of saliva production in the morning hours at a temperature of 37 oC with higher body weight. Therefore, our study infers biological rhythms in the leech Hirudinaria granulosa.