Does mating negatively affect female immune defences in insects?

Abstract

Immunity is an important mechanism of protection against pathogens and parasites. One factor that can influence immunity is mating. During mating, male-derived materials are transferred to females, and the physical contact also involves the potential risk of sexually transmitted infections, and wounding. Thus, mating can challenge a female’s immune system. This review focuses on exploring how immunity and mating interact in female insects. Although mating has been shown to cause female immune responses in several species, the responses do not always match the observed resistance to pathogens/parasites. Mating up-regulates female immune responses while female resistance is reduced compared to virgin females in some species, and vice versa in other taxa. We discuss why mismatches occur and why post-mating female resistance differs among species, and suggest that measured immune responses may not correlate with female resistance. Also, the mating system will play a major role. Polyandrous mating systems can generate intense post-mating sexual conflict, which can impose high costs of mating on females. Reduced female post-mating resistance may be due to direct suppression of female immunity by males. Alternatively, polyandry may increase the risk of sexually transmitted infections. If this is the major factor driving female post-mating resistance, females of polyandrous species should have higher post-mating immunity. To date, there are insufficient numbers of studies to fully answer the question ‘does mating negatively affect female immune defences in insects?’ To elucidate the links between immunity and mating in females, we need more studies in more species with varied mating systems.

Molecular insights into post‐mating immune response in a fish with internal fertilization

“…Indeed, although this may be true in some species, the universality of this ‘pre‐emptive strike’ response (Peng, Zipperlen, & Kubli, 2005) has been recently challenged by several studies showing that the components of the ejaculate (sperm and seminal fluid) are immunogenic to females (Lawniczak et al, 2007; Morrow & Innocenti, 2012). Moreover, although the activation of an immune response by females after mating has been reported in many species (Johansson, Bromfield, Jasper, & Robertson, 2004; Robertson, 2005; Wigby, Suarez, Lazzaro, Pizzari, & Wolfner, 2019), in other species the opposite occurs, and mating has instead an immune suppressant effect on females (Fedorka & Zuk, 2005; McKean & Nunney, 2001; Oku, Price, & Wedell, 2019; Rolff & Siva‐Jothy, 2002). Interpreting this down‐regulation of the immune function (or part thereof) triggered by mating invokes different, nonmutually exclusive, explanations.…”

Mating enhances immune function of Drosophila melanogaster populations against bacterial pathogens

“…Post mating immune function is the ability of an organism to resist harmful pathogens after becoming susceptible to infection due to mating (Oku et al, 2019). The probability to survive possible infection post mating, is not always correlated to sub-organismal immune response (measured in terms of encapsulation, haemocyte load, prophenoloxidase and phenoloxidase activity, lytic activity, gene expression, etc.)…”

“…The probability to survive possible infection post mating, is not always correlated to sub-organismal immune response (measured in terms of encapsulation, haemocyte load, prophenoloxidase and phenoloxidase activity, lytic activity, gene expression, etc.) to mating process itself (Adamo, 2004; Fedorka et al, 2007; Oku et al, 2019; Zuk and Stoehr, 2002). We, therefore, only deal with post mating immune function measured in terms of survival (probability of surviving) or hazard function (probability of death) as a measure of overall immunity in this study.…”

Differences in post-mating transcriptional responses between conspecific and heterospecific matings inDrosophila

“…However recent evidence suggests that the magnitude and direction of post-mating 520 immune responses varies across study systems and may have additional 521 explanations [39,41,[87][88][89][90]. In particular, several studies suggest that male ejaculate 522 components can be "immunogenic" such that they are directly triggering immune 523 responses in females [89].…”

“…JAK/STAT) are exacerbated in the heterospecific cross and may be a 528 consequence of divergent ejaculate components. Overall the D. novamexicana system 529 provides a unique opportunity to investigate the consequences of post-mating immune 530 activation and can provide a tractable experimental system to uncouple hypotheses of 531 immune activation as a reproductive process or pathogen defense mechanism [87,90].…”