Ultrastructure of the malpighian tubules of blow fly larva, Calliphora erythrocephala Meigen (Diptera : Calliphoridae)

Abstract

The Calliphora erythrocephala (Diptera : Calliphoridae) larva has 2 pairs of malpighian tubules. The right pair has 2 types of cells. The Type I cells are structurally analogous to the primary cells of the imaginal malpighian tubules. It comprises a wel-ldeveloped labyrinth of extracellular channels and an apical brush border, both containing mitochondria, and osmiophilic inclusions. The Type II cells, sparsely scattered among the Type I cells, are characterized by less extended basal infoldings and short apical microvilli devoid of mitochondria. We consider these cells (Type II) to be analogous to the stellate cells of the Calliphora imago tubule. The left pair, distinctly longer, comprises 3 different segments: the proximal segment is structurally and anatomically identical with the right tubules; the distal segment, spreading over almost the entire length of the body, is characterized by flattened epithelial cells (Type III) with basal infoldings and some short apical microvilli, and by numerous luminal concretions; some taller cells (Type IV), with a poorly developed labyrinth of extracellular channels and numerous slender apical microvilli, are observed at the tubule apex. The 2 segments are separated by a short intermediate segment. The characteristics of the ureter are similar to those of the midgut epithelium. This disparity in structural organization of the different cell types probably corresponds to some functional specializations.