Riboflavin instability is a key factor underlying the requirement of a gut microbiota for mosquito development

Significance Mosquitoes are major disease vectors that require a gut microbiota for development into adults under some conditions but not others. To determine the underlying mechanisms for this variation, we determined that dietary riboflavin rapidly decays under most environmental conditions that mosquitoes experience, which makes larvae reliant on their gut microbiota for this essential micronutrient. Our findings illustrate the value of being able to both control and manipulate dietary nutrients, microbiota composition, and environmental conditions in studying the role of gut microbes in animal biology. Our results also suggest environmental conditions are an understudied variable in why the gut microbiota is essential for provisioning certain essential vitamins in aquatic organisms like mosquito larvae.