Preliminary Studies On The Mechanisms Of Thermal Tolerance Of Tetrastichus Brontispae Ferrière

The coconut leaf beetle Brontispa longissima (Gestro) is an important invasion alien insect pest of coconut palms. Tetrastichus brontispae Ferriere is a parasitoid of B. longissima puma, and it was introduced into Hainan to control B. longissima pest in 2004 and released in the field. The biological, ecological and physiological mechanis-ms of thermal tolerance of T. brontispae were systematically studied in this article. The main results are summarized as follows.1. Effects of heat stress on the survivals of T.brontispaeThe survivals of T.brontispae at the three tested developmental stages were decreased with the increase of temperature during the same exposure times. The survivals of T.brontispae at the three tested developmental stages were decreased with the increase of time after exposed to 42℃. The survival rates were 0% and 26.67% after the larva and pupa of T.brontispae had exposed to 42℃for 12 h, and the survival rates were 7.78% and 0% after the female adults and the male adults of T.brontispae had exposed to 42℃for 5 h. Under the same conditions, the pupa of T.brontispae had the abilities of thermal tolerance higher than the larvae, and the abilities of thermal tolerance of the female adults of T.brontispae were higher than the male adults.2. Effects of heat stress on the development and fecundity of T.brontispaeThe development and fecundity of the next generation of T.brontispae were significantly affected after T.brontispae had exposed to high temperature.The development duration prolonged, successful parasitism rate decreased, number of wasps per mummy decreased, female ratio increased, longevity shorten declined with the increase of temperature after the egg, larvae and pupa of T.brontispae had exposed to the range from 33℃to 42℃for 8 h. While the development duration prolonged, number of wasps per mummy decreased, female ratio increased with the increase of temperature after the aduts of T.brontispae had exposed to the range from 33℃to 42℃for 8 h.The development duration prolonged, successful parasitism rate decreased, number of wasps per mummy decreased, female ratio increased, longevity shorten declined with the increase of time after the egg, larvae and pupa of T.brontispae had exposed to 42℃for different times. While the development duration prolonged, successful parasitism rate decreased, number of wasps per mummy decreased, female ratio decreased, longevity prolonged declined with the raise of temperature after the aduts of T.brontispae had exposed to 42℃for different times.The thermal sensitivity of different development stage of T. brontispae were grearly affected under high temperature, and the sensitivity order was egg＞larvae＞pupa.3. Effects of heat stress on Protective Enzymes of T.brontispaeThe activities of protective Enzymes in the larvae,pupa and adults of T.brontispae were determined after exposed to 30℃,33℃,36℃,39℃and 42℃by using spectrophotometric method. The results showed that the activities of CAT in the larvae, pupa and adults of T.brontispae after exposed to different high temperatur-es were increased while temperature rising. The activities of CAT in the larvae and pupa of T.brontispae were higher than that common in the same conditions.39℃was the suitable temperature which H2O2 was scavenged by CAT, the activities of CAT were inhibited above 39℃. The activities of POD in the larvae of T.brontispae after exposed to different high temperatures was higher than that common in the same conditions, while pupa and adult of T.brontispae were lower. The activities of POD in the larvae of T.brontispae were stimulated initially when the temperature reach to 33℃, and then inhibited with the increase of temperature. The activity of POD in the pupa and adult of T.brontispae were increased with the increase of temperature. The activities of SOD of T.brontispae after exposed to different high temperatures increased with the increase of temperature, and the activities of SOD in the larvae and pupa of T.brontispae were higher than that common in the same conditions, the activities of SOD in the adult of T.brontispae arrived to the highest when the temperature reach to 39℃and lower than that common in the same conditions.The activities of CAT in the larvae and pupa of T.brontispae after exposed to 42℃were decreased while temperature rising. The activities of CAT in the adults of T.brontispae were first increased and then decreased while temperature rising, and the activities of CAT arrived to the highest when the adults of T.brontispae exposed to 42℃for 3 h. The activities of POD in the larvae and adults of T.brontispae after exposed to 42℃were decreased while temperature rising. The activities of POD in the pupa of T.brontispae were first increased and then decreased while temperature rising, and the activities of POD arrived to the highest when the pupa of T.brontispae exposed to 42℃for 3 h. The activities of SOD in the larvae and adults of T.brontispae were first increased and then decreased while temperature rising, and the activities of SOD arrived to the highest when the larvae of T.brontispae exposed to 42℃for 8 h while the larvae of T.brontispae was 3 h. The activities of SOD in the pupa of T.brontispae after exposed to 42℃were increased while temperature rising.