Fig. 7a–d.

Nephrocytes in the fruit fly, Drosophila melanogaster. a Nephrocytes are detected by in situ hybridization for cathepsin B1 mRNA in larval fruit fly (arrowheads), and they are localized beside the heart tube. H Heart tube, T trachea. b, c Transmission electron micrographs of nephrocytes. Abundant endocytotic vesicles and well-developed lysosomes are characteristic in nephrocytes, which are crucial for the quality control of hemolymph. Nephrocytes protrude numerous foot processes adhering to the basement membrane and possess a slit diaphragm between the foot processes (c). d Comparison of cellular interdigitation and basal invagination in epithelial cells. The foot processes are formed by cellular interdigitation in podocytes and invagination of basal plasma membrane in nephrocytes. Thus, the slit diaphragm is an intercellular junction in podocytes and an autocellular junction in nephrocytes. Bars a 50 μm, b 5 μm, c 200 nm