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Abstract Maternally transmitted microbes are ubiquitous. In insects, maternal microbes can play a role in mediating the insect immune response. Less is known about how ecological factors, such as resource use, interact with maternal microbes to affect immunity.In the context of a recent colonization of a novel host plant by the Melissa blue butterflyLycaeides melissa, we investigated the interaction between host plant use and vertically transmitted, extracellular egg‐associated microbes in determining the strength of the insect immune response.We reared larvae on two different host plant species: a native hostAstragalus canadensisand a novel hostMedicago sativa. Egg‐associated microbes were removed through a series of antimicrobial egg washes prior to hatching. Immune response was measured through three assays: standing phenoloxidase (PO), total PO and melanization.We detected strong effects of microbial removal. Egg washing resulted in larvae with an increased immune response as measured by total PO—contrary to reports from other taxa. The effect of washing was especially strong for larvae consuming the native host plant.This result may explain why consumption of the egg casing is not a universal behaviour in insects, due to negative effects on larval immunity. Read the freePlain Language Summaryfor this article on the Journal blog.
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This content will become publicly available on July 3, 2025
Causes and consequences of microbiome formation in mosquito larvae
Abstract The assembly of host‐associated microbial communities is influenced by multiple factors, but the effect of microbiomes on host phenotypes is often not well understood. To address questions of food‐web effects on host microbiome assembly, we manipulated the resource environment (grass only [G] vs. grass + nutrients [GN]), competition type (intra‐ vs. inter‐specific) and density (high vs. low) forCulex restuans mosquito larvae. We predicted the microbial communities in fourth‐instar larvae would differ between these environmental treatments and that these treatments would translate into differences in the adult phenotype.Resource environment and density influenced the larval microbiome. In addition, the larval microbiome exhibited notable differences compared to the free‐living microbial communities.Resource‐driven differences in the larval samples can be attributed to Arcobacteraceae being more abundant in larvae reared in the GN treatments relative to those reared in the G treatments and Comamonadaceae being more abundant in the G treatment. Although significant, the difference in community structure between density treatments was difficult to discern. This appears to be driven by Weeksellaceae only being abundant in the high‐density, interspecific, GN treatment.Rearing larvae to adulthood under severe food limitation resulted in low survival (<25%) in both resource environments. Approximately 60% of survivors to adulthood were male. Larvae reared in the intraspecific, G treatment had the shortest development time to adulthood and emerged as the smallest adults.These results demonstrate how environmental variation can significantly alter the alpha and beta diversity of free‐living microbes, which in turn can significantly affect host phenotype and critical life history traits, such as development time, size at adulthood, and survival. These findings highlight the importance of considering environmental influences on microbiome diversity to understand and predict host outcomes, offering valuable insights for diverse applications in fields such as ecology, public health, and agriculture.
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- PAR ID:
- 10552786
- Publisher / Repository:
- Ecological Entomology
- Date Published:
- Journal Name:
- Ecological Entomology
- ISSN:
- 0307-6946
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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