Sthandiwe Nomthandazo Kanyile

 

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The impact of tyrosine-supplementing symbionts on the ecology of grain pest beetles.

Beetles are exceptional in their adaptability to the natural environment. Over time they have optimised their body design, which has allowed them to occupy an extensive range of habitats. Their evolutionary success can largely be attributed to their tanned, thick and hard cuticle, which has a multitude of functions, protecting beetles from biotic and abiotic stressors. For instance, the cuticle not only plays a role in camouflage, thermoregulation and desiccation resistance, but it also serves as an important first line of defence against predators and pathogens. Importantly, the hardening and tanning of the cuticle relies on tyrosine, a semi-essential amino acid which insects cannot synthesise themselves. Insects can thus uptake tyrosine through a proteinaceous diet or partner with microbes which can supplement them with this amino acid. Indeed, symbiosis with tyrosine-supplementing microbes has been reported in several beetle families.

The acquisition of these symbionts therefore, would have allowed beetles to explore and occupy new niches, particularly allowing them to exploit food sources of low-tyrosine content without foregoing their strong armour. One such niche that beetles have notoriously managed to colonise are grain storage facilities where they occur as pests. Symbiont presence/absence has been demonstrated to affect beetle phenotype, and suppression or elimination of these symbionts results in thinner, less melanised or even deformed cuticles.  Through the experimental manipulation of symbiont status, I will attempt to unravel how this symbiosis affects the ecology of grain pest beetles. Particularly, I will investigate if, through their contribution to cuticle development, symbionts mediate predator and pathogen defence, desiccation resistance, gut homeostasis and immunity in 2 species of grain pest beetles.

 

Publications

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2020

Engl, T., Schmidt, T. H. P., Kanyile, S. N. & Klebsch, D. (2020) Metabolic cost of a nutritional symbiont manifests in delayed reproduction in a grain pest beetle. Insects 11:717. doi: 10.3390/insects11100717