Immune function differences between two color morphs of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) at different life stages. Issue 10 (31st March 2021)

• Record Type: Journal Article
• Authors: Wang, Guihua; Zhou, Yuxuan; Tang, Baozhen; Ali, Habib; Hou, Youming
• Is Part Of: Ecology and evolution. Volume 11:Issue 10(2021)
• Page Start: 5702
• Page End: 5712
• Publication Date: 2021-03-31
• Subjects: antimicrobial activity -- cuticle pigmentation -- hemocyte -- immune response -- melanism -- pathogen resistance -- phenoloxidase; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.7474
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Several studies demonstrated that in insects cuticle melanism is interrelated with pathogen resistance, as melanin‐based coloration and innate immunity possess similar physiological pathways. For some insects, higher pathogen resistance was observed in darker individuals than in individuals with lighter cuticular coloration. Here, we investigated the difference in immune response between two color morphs (black and red) and between the life stages (pupa and adult) of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae). Here in this study, cuticle thickness, microbial test (antimicrobial activity, phenoloxidase activity, and hemocyte density), and immune‐related gene expression were evaluated at different stages of RPW. Study results revealed that cuticle thickness of black phenotype was thicker than red phenotype at old‐pupa stage, while no significant difference found at adult stage. These results may relate to the development processes of epidermis in different stages of RPW. The results of antimicrobial activity, phenoloxidase (PO) activity, and hemocyte density analyses showed that adults with a red phenotype had stronger pathogen resistance than those with a black phenotype. In addition to antimicrobial activity and PO activity, we tested relative gene expression in the fat body of old pupae. The results of hemolymph antimicrobial analysis showed that old pupae with a red phenotype were significantly different from those with a black phenotype at 12 hr after Staphylococcus aureus injection, suggesting that red phenotype pupae were more sensitive to S. aureus . Examination of gene expression in the fat body also revealed that the red phenotype had a higher immune response than the black phenotype. Our results were inconsistent with the previous conclusion that dark insects had increased immune function, suggesting that the relationship between cuticle pigmentation and immune function in insects was not a direct link. Additional possible factors that are associated with the immune response, such as life‐history, developmental, physiological factors also need to be considered. Abstract : This paper reported pathogen resistance differences between two different segmental ventral colorations in the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) (red phenotype and black phenotype) and investigated immune function in the old‐pupa and adult stages. Our results showed cuticle melanism pigmentation does not correspond to enhanced immune function in RPW, which were inconsistent with the previous conclusion that dark insects had increased immune function. We suggest that evaluation of the relationship between cuticle pigmentation and immune function in insects needs to also consider additional possible factors that are associated with the immune response, such as life‐history, developmental, and physiological factors.