Interpretation of the morphological adaptations associated with viviparity in the Tsetse fly (Glossina morsitans) by three dimensional analysis

Abstract Tsetse flies (genus Glossina ), the sole vectors of African trypanosomiasis, are distinct from other disease vectors, and most other insects, due to dramatic morphological and physiological adaptations required to support their unique life histories. These evolutionary adaptations are driven by demands associated with their strict dietary and reproductive requirements. Tsetse reproduce by obligate viviparity which entails obligate intrauterine larval development and provisioning of nutrients for the developing larvae. Viviparous reproduction reduces reproductive capacity/rate which also drives increased inter- and intra-sexual competition. Here, we use phase contrast microcomputed tomography (pcMicroCT) to perform a three-dimensional (3D) analysis of viviparity associated morphological adaptations of tsetse female reproductive tract. These include 1) abdominal modifications facilitating the extreme abdominal distention required during blood feeding and pregnancy; 2) abdominal and uterine musculature required for parturition of developed larvae; 3) reduction of ovarian structure and capacity; 4) structural features of the spermatophore form in the female uterus to enhance semen/sperm delivery and inhibition of insemination by competing males; 5) uterine morphological features facilitating expansion and contraction before, during and after pregnancy; 6) milk gland structural optimizations facilitating nutrient incorporation and transfer into the uterus. The use of pcMicroCT provides unprecedented opportunities for examination and discovery of internal morphological features not possible with traditional microscopy techniques and new opportunities for comparative morphological analyses over time and between species.