[Fully-funded studentship covering fees, maintenance stipend (£20,780 p.a. for 2025/26), and research training and support grant (RTSG). International applicants may have the difference between 'home' and 'international' fees waived, but relocation, visa, and health surcharge costs are not covered.] This PhD studentship at the University of East Anglia investigates the evolution of egg defences in the medfly (Ceratitis capitata), a major global agricultural pest. The project is supervised by Professor Tracey Chapman and is embedded within the ARIES Ecology and Biodiversity theme, offering strong interdisciplinary training in phenotypic and molecular genetic engineering. The research focuses on how medfly mothers protect their eggs by cloaking them with potent, broad-spectrum antimicrobial peptides known as Ceratotoxins, which are encoded by seven genes. These peptides kill microbes by disrupting their membranes, and eggs lacking these protective compounds show slower development, highlighting their evolutionary benefits. The project aims to determine the overall fitness benefits of Ceratotoxin egg cloaks under natural conditions, the functional significance of Ceratotoxin gene redundancy, and the potential application of Ceratotoxins in insect control strategies. Methodologies include phenotypic manipulations (such as egg cloak removal and microbial add-backs), sequencing of microbial communities (16S rDNA), and molecular genetics approaches like CRISPR-Cas9 knock-outs of Ceratotoxin gene combinations. The student will also explore the antimicrobial spectrum and potency of synthetic Ceratotoxin peptide mixtures and assess the fitness of gene-edited medflies. Depending on interests, the project may extend to experimental, modelling, or quantitative literature synthesis approaches to evaluate Ceratotoxin use in pest control, including engineering solutions to reduce host fitness or improve the health of mass-reared strains for sterile release. Training will cover technical skills in bioinformatics, molecular genetics, microbiology, and phenotype engineering, as well as transferrable skills such as critical thinking, ethics, and Open Research. The research environment is described as thriving, respectful, and inclusive. The studentship is fully funded for eligible UK and international candidates, covering tuition fees, a maintenance stipend (£20,780 p.a. for 2025/26), and a research training and support grant. International students may have the difference between home and international fees waived, but must cover their own relocation, visa, and health surcharge costs. Applicants should have a strong background in Biological Sciences, Genetics, or Ecology, with at least a UK 2:1 Honours degree and meet English language requirements (IELTS 6.5 overall, 6 in each category). The position is available for full-time or part-time study, starting 1 October 2026. Applications are submitted via the University of East Anglia’s postgraduate research portal, with a deadline of 7 January 2025.