Subtle effect of Xenos vesparum (Xenidae, Strepsiptera) on the reproductive apparatus of its male host: Parasite or parasitoid?

Abstract

A B S T R A C TParasitic castration is an adaptive strategy where parasites usurp the hosts' reproductive physiology to complete their life cycle. The alterations in the host traits vary in their magnitude, from subtle changes in the host morphophysiology and behaviour to the production of complex aberrant phenotypes, which often depend on the host gender. The strepsipteran macroparasite Xenos vesparum induces dramatic behavioural and physiological changes in its female host, the paper wasp Polistes dominula, while its effect on the male phenotype is largely unknown.In this study we investigated how a single X. vesparum parasite influences the functional morphology of P. dominula male reproductive apparatus. We performed morphometry and ultrastructure characterization of corpora allata, testes, seminal vesicles and accessory glands in parasitized and unparasitized males, and also in young and old males to control for the effect of age on the natural deterioration of these organs. Our results show that age significantly affects the development of male reproductive apparatus. A low parasite load -one parasite per host is the common prevalence in the field -has only a marginal impact on the reproductive morphology of P. dominula males, affecting quantitatively but not qualitatively the protein content of male accessory glands. Thus, in male P. dominula wasps, X. vesparum appears to behave as a true "parasite", in clear opposition to the role of "parasitoid" that it takes in female hosts where castration causes the reproductive death.

Caste, sex, and parasitism influence brain plasticity in a social wasp

“…They also showed a significant increase in the volume of several sensory brain regions, including the antennal and optic lobes, and two substructures of the calyx: lip and collar. Remarkably, neuroendocrine manipulation does not seem to occur in parasitized males, as they can still develop their testes and attempt to mate with females (Beani et al 2017;Cappa et al 2014). The inability to hinder male reproduction may likely result in a tradeoff with brain manipulation, which is an expensive tissue to produce (Keesey et al 2020;Niven and Laughlin 2008).…”

“…We also predict a higher effect in brain plasticity towards parasitized workers, which are castrated and show aberrant behaviors, compared to parasitized males who reproduce and show no changes in behavior. Finally, we expand on studies that reported reduced corpora allata in parasitized females and males compared to non-infected conspecific by testing for the effect of parasite sex (Beani et al 2017;Strambi and Strambi 1973).…”

Options for the biological and physical control of Vespa velutina nigrithorax (Hym.: Vespidae) in Europe: A review

“…This rate may be different in Europe and with V. velutina and should be further studied. Therefore, X. moutoni and the closely related species Xenos vesparum, which is also a parasitizing hymenopters (Beani et al, 2017), may also be good candidates for the biological control of V. velutina.…”

Cuticular hydrocarbons as cues of sex and health condition in Polistes dominula wasps

“…2, 3). Noticeably, host sex is a critical factor also for morphological and behavioural changes driven by parasites: the primary targets of infection is workers and gynes, which are castrated by the parasite, whereas minor morphological effects (a subtle change in accessory gland secretion) were found in parasitized males that were sexually active in leks and not castrated Beani et al 2017). Here, we did not consider parasite load, because P. dominula wasps rarely harbour more than one parasite (Hughes et al 2004b).…”