Figure 3

(A–F) Transmission electron micrograph of the lungs of the semifossorial African giant pouched mole rat Cricetomys gambianus (A) and that of the underground dwelling (subterranean) Nigerian mole rat Cryptomys foxi (B) showing type-II (granular) pneumocytes (asterisks). BC, blood capillaries containing erythrocytes (Er); circles, clear areas which in life form the osmiophilic lamellated bodies which are the precursors of the surfactant; Mt, mitochondria; Al alveoli; Co, collagen fibers. Transmission electron micrographs of the lungs of C. gambianus (C) and that of C. foxi (D) showing alveolar macrophages (Mp) located on the alveolar surface (C) and one passing through the interalveolar pore (D). Encircled areas, electron dense bodies that constitute the lysosomes; boxed areas, clusters of mitochondria; arrows, filopodia; BC, blood capillaries containing erythrocytes (Er); Pl, platelets; Co, collagen fibers; Al, alveoli. Transmission electron micrographs of the blood-gas barriers of the lungs of C. gambianus (E) and that of C. foxi (F) showing the blood-gas (tissue) barrier that comprises an epithelial cell (asterisk), a common basement membrane (dots) and an endothelial cell (stars). BC, blood capillary; Er, erythrocytes; Al, alveolus. On (F), an alveolar macrophage (Mp) lies next to the blood-gas barrier (boxed area). The arrows and the circles respectively show filopodia and lysosomes of the alveolar macrophage.