Fig 2

The morphology of pulmonary migration. a Cast showing the complex meshwork of short capillaries that surround each alveolar space, in contrast to more normal capillaries at the periphery (arrow). BV, blood vessel. The mean diameter of mouse alveoli ranges from 36 to 45 μm, depending on strain while the diameter of an alveolar capillary is ~ 6 μm. Image from Guntheroth et al. [35] with permission. b Dark-field image of a Day 2 schistosomulum prior to exit from the skin via a blood vessel. c Dark-field image of a fully extended Day 6 lung schistosomulum, approximately 400 μm in length. When crossing the vascular bed, the parasite body must extend through the capillary labyrinth of several alveoli (b and c from [29]). d Transmission electron micrograph of a part of a lung schistosomulum lying within the lumen of an alveolar capillary. The tight squeeze is confirmed by the bulge in the body where it lies adjacent to another capillary (arrowed) (from [30]). e Diagrammatic representation of the way that a schistosomulum uses its anterior and posterior body spines to move along the capillary lumen, alternately anchoring one set and then the other (from [36]). Scale-bars in a–c: 50 μm