Three-dimensional analysis and visualization of morphological adaptations associated with viviparity in the Tsetse fly (Glossina morsitans).

Tsetse flies (genus Glossina), the sole vectors of African trypanosomiasis, are distinct from other disease vectors, and most other insects, due to dramatic evolutionary adaptations required to support their unique life history. These morphological and physiological 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. This work describes three-dimensional (3D) analysis of viviparity associated morphological adaptations of tsetse female reproductive tract as well as that of male seminal secretions by phase contrast microcomputed tomography (pcMicroCT). Structural features of note include abdominal modifications facilitating the extreme abdominal distention required during blood feeding and pregnancy; abdominal and uterine musculature required for parturition of developed larvae; reduction of ovarian structure and capacity; structural features of the male seminal spermatophore that enhance sperm delivery and inhibition of insemination by competing males; uterine morphological features facilitating expansion and contraction before, during and after pregnancy; analysis of structural optimizations of the milk gland 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.