摘要
Abstract Dendroctonus-fungus symbioses are often considered as the ideal model sys- tems to study the development and maintenance ofectosymbioses, and diverse interactions, including antagonism, commensalism and mutualism, have been documented between these organisms. The red turpentine beetle, Dendroctonus valens LeConte （Coleoptera： Curculionidae： Scolytinae） is a pine-killing invasive beetle in northern China. Fungi species Ophiostoma minus, Leptographium sinoprocerum, L. terebrantis and L. procerum were associated with this bark beetle. Antagonistic interactions between D. valens and its as- sociated fungi, such as O. minus and L. sinoprocerum, have been demonstrated, but the underlying causes of this phenomenon are unknown. Here, we first found the two tested fungi species retarded the net weight gain of D. valens larvae after completing 3-day feeding on their media. Furthermore, we provide direct evidence indicating the effect of associated fungi on the immunocompetence olD. valens larvae to explain the documented antagonism. Our results showed that the activity of phenoloxidase and total phenoloxi- dase in D. valens larvae were significantly upregulated by two strains of associated fungi, O. minus and L. sinoprocerum as compared with the controls. The phenoloxidase ratio increased significantly in the larvae which had fed for 3 days on media inoculated with O. minus. Because insect immtme defenses are costly to be deployed, these results could be explored as one of the underlying mechanisms of the documented antagonism.
Abstract Dendroctonus-fungus symbioses are often considered as the ideal model sys- tems to study the development and maintenance ofectosymbioses, and diverse interactions, including antagonism, commensalism and mutualism, have been documented between these organisms. The red turpentine beetle, Dendroctonus valens LeConte （Coleoptera： Curculionidae： Scolytinae） is a pine-killing invasive beetle in northern China. Fungi species Ophiostoma minus, Leptographium sinoprocerum, L. terebrantis and L. procerum were associated with this bark beetle. Antagonistic interactions between D. valens and its as- sociated fungi, such as O. minus and L. sinoprocerum, have been demonstrated, but the underlying causes of this phenomenon are unknown. Here, we first found the two tested fungi species retarded the net weight gain of D. valens larvae after completing 3-day feeding on their media. Furthermore, we provide direct evidence indicating the effect of associated fungi on the immunocompetence olD. valens larvae to explain the documented antagonism. Our results showed that the activity of phenoloxidase and total phenoloxi- dase in D. valens larvae were significantly upregulated by two strains of associated fungi, O. minus and L. sinoprocerum as compared with the controls. The phenoloxidase ratio increased significantly in the larvae which had fed for 3 days on media inoculated with O. minus. Because insect immtme defenses are costly to be deployed, these results could be explored as one of the underlying mechanisms of the documented antagonism.
