Repeated evolution of morphological characters in ecomorphs of avian feather lice

Chewing lice are permanent ectoparasites of birds, living their entire life cycle on their hosts. These lice feed on feathers and if uncontrolled will cause massive damage to downy feathers. The main defenses birds have against lice are preening with the bill and scratching with the feet. Chewing lice have repeatedly evolved into various ecomorphs that live on different parts of the host’s body and differ in how they escape host defense. For example, ‘wing lice’, are long and slender in shape, and fit between barbs of the bird’s wing feathers to avoid being removed by preening. In contrast, ‘head lice’ have a plump, rounded body with a triangular head, supporting strong mandibular muscularization, helping them to grip feather barbs to avoid being removed by scratching. While it has been shown phylogenetically that these ecomorphs have repeatedly evolved, the morphological structures associated with each ecomorph are less well known. We will discuss differences in morphological adaptations across multiple ecomorphs (e.g. volume of lower mandibular adductor muscles) using data from micro Computed Tomography (microCT) scans. The microCT allows us to visualize the structures within each louse in three dimensions allowing quantitative measurements and observations unavailable on traditional slide mounted preserved specimens.