Effect of temperature on hatching and viability of the eggs of Bunostomum trigonocephalum Rudolphi, 1808

The effect of temperature on the hatching and viability of the eggs of Bunostomum trigonocephalum in a tropical climate is described. All experiments were performed with 500 eggs in each dish of saline medium. Experiments on hatching of eggs at any one temperature were repeated twelve times and on viability of eggs eight times.

The range of temperature for hatching was found to be 10–34 °C. The time for commencement and for termination of hatching of eggs (in hours) was 18 and 48 at 34 °C, 21 and 51 at 30 °C, 24 and 54 at 25 °C, 45 and 78 at 20 °C, 77 and 119 at 15 °C, and 264 and 360 at 10 °C.

The rate of hatching of eggs was observed at temperatures of 10, 15, 20, 25, 30 and 34 °C. Maximum hatching took place at 34 °C, which is also the optimum temperature for hatching. At a temperature of 10 °C, 98–99% of the eggs did not develop.

The viability of eggs was observed at temperatures above and below the hatching range. Eggs remained viable up to 7 h at – 10 °C, 5 days at 0 °C, 7 days at 5 °C, 10 h at 35 °C, 6 h at 40 °C, 1 h at 45 °C, and 20 min at 50 °C.

The authors wish to acknowledge a research grant from the Scientific Research Committee, Uttar Pradesh, India. We also express our thanks to Professor M. B. Lal for his kind encouragement and interest throughout this study.