Cuticle enhancing symbionts for a durable and waterproof armour: How nutritional symbionts enhance protection against natural enemies and desiccation in grain pest beetles

Sunday, November 13, 2022

2:06 PM – 2:18 PM PT

Location: Vancouver Convention Centre, Meeting Room 208/209

Presenting Author(s)

Sthandiwe N. Kanyile

PhD Candidate
Max Planck Institute for Chemical Ecology
Jena, Thuringen, Germany

Co-Author(s)

Tobias Engl

Max Planck Institute for Chemical Ecology
Jena, Thuringen, Germany
Martin Kaltenpoth

Director
Max Planck Institute for Chemical Ecology
Jena, Thuringen, Germany

Several beetle families engage in mutualistic associations with symbionts that provide the host with precursors for the semi-essential amino acid tyrosine that is required in high amounts for the biosynthesis of the beetles’ hard and dark cuticle. However, how these symbioses mediate the host’s interactions with biotic and abiotic stressors is often neglected. By manipulating the symbiosis of two grain pest beetles, we here demonstrate how symbiont-mediated cuticle biosynthesis 1) enhances host defence against predation and fungal infection and 2) improves host resistance to desiccation. First, we exposed age-defined symbiotic and symbiont-depleted (aposymbiotic) Oryzaephilus surinamensis beetles to a predator and pathogen that attack via the cuticle. While young beetles suffered from high predation and fungal infection rates regardless of symbiont presence, symbiotic beetles were able to escape this period of vulnerability earlier, reaching high survival probabilities faster than aposymbiotic beetles. A time-series analysis of cuticle development in symbiotic and aposymbiotic beetles revealed that symbionts accelerate their host’s cuticle formation; enabling it to quickly reach a cuticle quality threshold that confers structural protection against predation and fungal infection. Second, we investigated if cuticle-enhancing symbionts of the cereal rice weevil Sitophilus oryzae improve desiccation resistance. For this, we exposed symbiotic and aposymbiotic weevils to chronic and acute desiccation stress. By measuring survival, population growth and cuticular hydrocarbon profiles of both treatments under dry conditions, we show how the rice-weevil symbiosis improves host resistance to desiccation. Our findings demonstrate how nutritional symbioses can have important ecological implications reaching beyond the immediate nutrient-provisioning benefits.