Is Sexual Dimorphism in the Immune Response of Gryllodes sigillatus Related to the Quality of Diet?

Abstract

Whereas some authors have proposed that sexual dimorphism in the immune response is fixed, others pose that it is dynamic and depends on diet. The aim of the present study was to explore the second hypothesis. Immunocompetence differences between females and males can be linked to resource availability. We tested this idea by providing a low or high quality diet to two groups of Gryllodes sigilatus during their developmental period. Then, at the adult phase half of each group was challenged with LPS from Serratia marcescens. The size, phenol oxidase (PO), and lytic activity were compared between groups according to diet, sex, and immune challenge. Results show that diet quality favor size in both sexes. However, the overall immune response did not seem to be significantly different based on diet, but instead on sex. Females showed greater phenol oxidase levels than males, but the opposite was found with lytic activity. Perhaps in G. sigillatus the differences in the pathogens commonly confronted by each sex in the distinct habitat of each could explain the differences on PO and lytic activity.