Immune function differences between two color morphs of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) at different life stages

Guihua Wang; Yuxuan Zhou; Baozhen Tang; Habib Ali; Youming Hou

doi:10.1002/ece3.7474

Immune function differences between two color morphs of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) at different life stages

Ecol Evol. 2021 Mar 31;11(10):5702-5712. doi: 10.1002/ece3.7474. eCollection 2021 May.

Authors

Guihua Wang^{1

2

3}, Yuxuan Zhou^{1

2

3}, Baozhen Tang^{1

2

3}, Habib Ali^{1

4

5}, Youming Hou^{1

2

3}

Affiliations

¹ State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops Fujian Agriculture and Forestry University Fuzhou China.
² Key Laboratory of Biopesticide and Chemical Biology Ministry of Education Fujian China.
³ Fujian Province Key Laboratory of Insect Ecology College of Plant Protection Fujian Agriculture and Forestry University Fujian China.
⁴ Department of Agriculture Engineering Khawaja Fareed University of Engineering and Informtion Technology Rahim Yar Khan Pakistan.
⁵ University of Agriculture Faisalabd Okara Pakistan.

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.

Keywords: antimicrobial activity; cuticle pigmentation; hemocyte; immune response; melanism; pathogen resistance; phenoloxidase.