Territorial damselflies do not show immunological priming in the wild

Abstract

Adaptive immunity allows vertebrates to gain protection against repeated pathogenic infections. Analogous responses (priming) have been recently uncovered in invertebrates. However, whether such responses are widespread is not known. The present study investigated the presence of immunological priming in males of a species whose phylogenetic position places it in one of the less derived insect orders. It is hypothesized that the efficiency of such a response could be related to animal condition, as assessed by the expression of a sexually selected ornament. Hetaerina americana Fabricius (Odonata: Calopterygidae) males bear a conspicuous ornament (a red wing spot), which is evolutionarily maintained via male territorial competition. Using field-collected animals, a group of males is challenged with bacteria before exposure to a higher dose of the same or a different bacteria, and survival is compared with that of infected males not previously challenged, as well as control groups. Grampositive and Gram-negative bacteria are used. To explore how long priming may take to work, the second exposure is carried out either after 1 or 5 days. Red spot and body size are entered in the analysis as predictors of survival within and between groups. There is no difference in survival among groups, which suggests no priming effect. Overall, red spot and body size are not consistent in explaining survival.

Exposure to Bacterial Signals Does Not Alter Pea Aphids’ Survival upon a Second Challenge or Investment in Production of Winged Offspring

“…Immune priming decreases susceptibility of some arthropods to some pathogens [3–5,10,31,32], but it is not universal to all insect-pathogen interactions [33,34]. Here, we saw no evidence of pre-exposure to bacterial elicitors impacting survival against two bacterial pathogens, even when, in the case of E.…”

Previous Exposure to an RNA Virus Does Not Protect against Subsequent Infection in Drosophila melanogaster

“…Other studies have found no evidence for priming at all [58]–[60]. Priming can also be variable within a host-parasite system, suggesting it may sometimes be context dependent [10], [61].…”

Insect immunology and hematopoiesis

“…It has been hypothesized that immune priming occurs because the insect is inherently able to activate immune responses more rapidly during a second exposure, or because pathogens or pathogen components are retained within the insect, which maintains the animal in a heightened state of immune alertness (Masri and Cremer, 2014). Although immune priming has been demonstrated in multiple insect orders, it is not a universal feature of the insect immune system, nor is it universal for all infection types (Gonzalez-Tokman et al, 2010; Reber and Chapuisat, 2012). …”