Figure 6.

CTEM of unstained, cryo preserved extruded Anncaliia algerae polar tubes containing cargo; consisting of membranes, cylinders, and sacs. Also note the PT surfaces covered with fibrillar and fine particulate structures.

A. Undulating or “S” shaped portion of a PT with layers of parallel alternating electron lucent and dense fine material with approximately 6–7 nm spacing between the dense layers (arrows). Bar is 50nm.

B. Organization of the PT is well preserved and multiple layers of varying densities are visible. The outermost surface edge is covered with fine fibrils (arrows). Bar is 50 nm.

C. Image of two PT segments that contain various forms of cargo. The upper tube has multiple layers of membrane-like material arranged parallel to the orientation of the tube and surrounding a narrow long cylinder (C). The lower PT contains membrane-like and tubular structures, some of which bend around cylinders (C). Bar is 50 nm.

D. Polar tube containing multiple layers of membrane–like material of varying densities some enclosing a cylinder (C). The outer-most surface edge is covered with fine fibrils Bar is 50 nm.

E. Polar tube with dense material or cylinders (C) encompassed by several membrane–like layers. Bar is 50 nm.

F. Polar tube contains a membrane enclosed sac (S) of medium dense particulate material and appears to be pinching off (broad arrows). Bar is 50 nm.

G. Polar tube containing several membrane enclosed sacs (S), of medium dense particulate material. A portion of the tube’s diameter overlaying the large sac is enlarged. The outer surface of the tube is covered with fine fibrillar material (arrows). Bar is 50 nm.

H. Polar tube containing membrane-like structures and dense material. The tube surface is covered with fine fibrils and small “clumps” of dense material at the end of some fibrils (arrows). Bar is 50nm.

I. The PT surface is covered with fine fibrils and dense particulate material (arrows). Inside the PT is a membrane limited undulating tube, giving a-tube-within-a–tube appearance similar to that observed in negative stained tube (Fig. 2.C). Bar is 50 nm.