Influence of the sex of galling insects on gall metabolism: The case of eriococcid galls

Abstract

Eriococcidae-induced galls may accumulate all sorts of primary and secondary plant metabolites, but as phloem suckers, such accumulation is commonly related to the maintenance of gall structure rather than to the galling insect nutrition. For galling Eriococcidae, the feeding activity of female and male insects may have different impact on the metabolic profile of the galls. Accordingly, even under the stimuli imposed by the same species, the morphological peculiarities of Eriococcidae galls are related to sexual dimorphism. The dimorphism has been explained by the differences in their lifespans, herein examined in Annona dolabripetala (Annonaceae)- Pseudotectococcus rolliniae (Eriococcidae) and Pseudobombax grandiflorum (Malvaceae)- Eriogallococcus isaias (Eriococcidae) systems. We assume that the galls induced by females with their longer life cycles generate a higher demand for metabolites than the galls induced by males, and check it out by analyzing the histochemical and anatomical profiles of the galls. The primary metabolites, starch, and lipids, accumulate only in the inner cortex of the female-induced galls of both species and may work out in the dissipation of reactive oxygen species (ROS), as the accumulation of these primary metabolites may consume ROS. Regarding the secondary metabolites, terpenoids accumulate in the inner and median cortices of the male-induced galls of the two host species. In the female-induced galls, secondary metabolites accumulate in the outer cortex where they can be related to the sexual attraction of the males to copulate with the sessile females inside the gall chamber. The female-induced galls on A. dolabripetala e P. grandiflorum, with their longer life cycles, accumulate a wider histochemical profile, corroborating our hypothesis.