Affiliation:
1. Mutualisms Research Group, Max Planck Institute for Biology, Tübingen 72076, Germany
2. Electron Microscopy Facility, Max Planck Institute for Biology, Tübingen 72076, Germany
Abstract
Faithful transmission of beneficial symbionts is critical for the persistence of mutualisms. Many insect groups rely on extracellular routes that require microbial symbionts to survive outside the host during transfer. However, given a prolonged aposymbiotic phase in offspring, how do mothers mitigate the risk of symbiont loss due to unsuccessful transmission? Here, we investigated symbiont regulation and reacquisition during extracellular transfer in the tortoise beetle,
Chelymorpha alternans
(Coleoptera: Cassidinae). Like many cassidines,
C. alternans
relies on egg caplets to vertically propagate its obligate symbiont
Candidatus
Stammera capleta. On average, each caplet is supplied with 12 symbiont-bearing spheres where
Stammera
is embedded. We observe limited deviation (±2.3) in the number of spheres allocated to each caplet, indicating strict maternal control over symbiont supply. Larvae acquire
Stammera
1 day prior to eclosion but are unable to do so after hatching, suggesting that a specific developmental window governs symbiont uptake. Experimentally manipulating the number of spheres available to each egg revealed that a single sphere is sufficient to ensure successful colonization by
Stammera
relative to the 12 typically packaged within a caplet. Collectively, our findings shed light on a tightly regulated symbiont transmission cycle optimized to ensure extracellular transfer.
Funder
Max Planck Society
Alexander von Humboldt-Stiftung
Subject
General Agricultural and Biological Sciences,General Environmental Science,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
Cited by
11 articles.
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