Effects of host plants and temperatures on digestive enzyme activities in Heterolocha jinyinhuaphaga larvae

Abstract

Objective This research aims to study the effects of host plants and temperatures on digestive enzyme activities in Heterolocha jinyinhuaphaga larvae, and lay a foundation for further research on their physiological and biochemical mechanism of environmental adaptation. Method Effects of these factors on digestive enzyme activities in H. jinyinhuaphaga larvae were studied through ultraviolet spectrophotometry and burette in laboratory by using 3, 5-dinitrosalicylic acid method, fulin-phenolic method, and standard sodium hydroxide solution titration method. Result Digestive enzyme activities of each H. jinyinhuaphaga larva differed after feeding on 'Jiufeng No. 1', 'Xiangshui No. 1', 'Xiangshui No. 2' and a wild variety of Lonicera japonica. The H. jinyinhuaphaga larvae feeding on the wild variety had the highest amylase, sucrase and protease activities, and the lowest lipase activity. The activities in the 1st instar larva were 18.37, 26.45, 22.31 and 5.54 mmol·g-1·min-1 respectively. The four digestive enzyme activities all increased with larval ages. Compared with the 1st instar larvae, the 5th instar larvae, after feeding on the four cultivars, displayed an increase in amylase activities by 33.39%, 27.48%, 33.31% and 45.29%, an increase in sucrase activities by 19.12%, 15.02%, 14.64% and 29.64%, an increase in protease activities by 25.55%, 18.69%, 21.69% and 41.46%, and an increase in lipase activities by 84.95%, 68.04%, 68.41% and 77.80%. In the range of 16-34℃, the activities of the four digestive enzymes all showed a tendency of first increasing and then decreasing with the rise of temperature. The highest amylase activities were observed at 22℃ in the larvae of the 1st-5th instar, which were 19.95, 20.57, 21.79, 23.64 and 25.86 mmol·g-1·min-1. The sucrase activities of the 1st-5th instar larvae were the highest at 22℃, which were 27.65, 28.89, 29.85, 31.45 and 32.89 mmol·g-1·min-1. The protease activities of the 1st-5th instar larvae were the highest at 25℃, which were 21.65, 22.76, 23.43, 25.71 and 26.98 mmol·g-1·min-1. The lipase activities of the 1st-5th instar larvae were the highest at 28℃, which were 7.38, 8.49, 9.81, 11.33 and 13.21 mmol·g-1·min-1. Two-way ANOVA showed that the interaction between host plants and larval ages, as well as the interaction between temperatures and larval ages, had no significant effect on the four digestive enzyme activities. Conclusion Host plants and temperatures can affect digestive enzyme activities of H. jinyinhuaphaga larvae.