Relationship between maternal transfer of immunity and mother fecundity in an insect

Abstract

Trans-generational immune priming (TGIP) corresponds to the plastic adjustment of offspring immunity as a result of maternal immune experience. TGIP is expected to improve mother's fitness by improving offspring individual performance in an environment where parasitism becomes more prevalent. However, it was recently demonstrated that maternal transfer of immunity to the offspring is costly for immunechallenged female insects. Thus, these females might not provide immune protection to all their offspring because of the inherent cost of other fitness-related traits. Females are therefore expected to adjust their investment to individual offspring immune protection in ways that maximize their fitness. In this study, we investigated how bacterially immune-challenged females of the mealworm beetle, Tenebrio molitor, provision their eggs with immune protection according to egg production. We found that immunechallenged females provide a variable number of their eggs with internal antibacterial activity along egg-laying bouts. Furthermore, within the first immune-protected egg-laying bout (2 -4 days after the maternal immune challenge), the number of eggs protected was strongly dependent on the number of eggs produced. Immune-challenged females might therefore adjust their investment into TGIP and fecundity according of their individual perception of the risk of dying from the infection and the expected parasitic conditions for the offspring.

Increased Survival in the Red Flour Beetle after Oral Priming with Bacteria-Conditioned Media

“…Fitness costs of immunity are generally assumed, based on life-history theory [37] and might, for example, be due to the expression of immune effectors that are costly to produce [38]. Similar costs were also found for septic, transgenerational immune priming [26,27]. By contrast, septic bacterial priming accelerated development in T. castaneum [39], which might be an adaptive modulation of life history by earlier reproduction.…”

“…Immune priming has been shown to come at a cost for the primed individual [26,27] and it may also have an impact on development time [28,29]. We therefore studied whether oral immune priming affected the growth and development of T. castaneum .…”

Endogenous egg immune defenses in the yellow mealworm beetle (Tenebrio molitor)

“…This species is well known as a model for innate immunity (Chae et al, 2012;Dobson et al, 2012;Goltsev et al, 2009;Johnston et al, 2014;Lee et al, 1996;Moon et al, 1994;Park et al, 2007Park et al, , 2006Yu et al, 2010;Zhang et al, 2003;Zhu et al, 2013Zhu et al, , 2014, but has also received considerable attention with respect to TGIP (Dubuffet et al, 2015;Moreau et al, 2012;Moret, 2006;Zanchi et al, 2012). Here we show that the eggs of T. molitor can induce immune genes, including antimicrobial peptides (AMPs), to high levels upon bacterial challenge.…”

The maternal transfer of bacteria can mediate trans-generational immune priming in insects

“…The direct transfer of immune-related factors (e.g., lysozymes or antimicrobial peptides) in the cytoplasm of the egg has been proposed. 3,12 An additional possibility is genomic imprinting, in which parental experience causes heritable alterations in gene expression that prime the offspring, thus highlighting the potential contribution of epigenetic effects on the inheritance of immunity. 13 A third but until now theoretical strategy, is the direct transfer of microbial fragments derived from bacteria encountered by the parent generation.…”

“…[1][2][3] Parents invest in their offspring by preparing them for defense against pathogens encountered only by the parent, a phenomenon known as specific trans-generational immune priming. This phenomenon has independently been discovered in the crustacean Daphnia magna, 4 and in insects such as the bumble bee.…”