Ultrastructure of the midgut and hindgut of Derocheilocaris remanei (Crustacea, Mystacocarida)

Ultrastructural features and structure of the midgut and hindgut of Deroche ilocaris remanei mere studied. The large endodermal midgut is differentiate d into an anterior midgut and a posterior midgut separated by a conspicuous constriction. Both circular and longitudinal striated muscle bands surroun d the midgut, while the hindgut only presents longitudinal muscles. The lim it between the midgut and the cuticle-lined hindgut is marked by a rectal v alve. In cross-section, the short hindgut is triradiate and has a distinct Y-shaped lumen. The hindgut cuticular lining appears interrupted at the tip of every branch of the Y. Three different cell types are found in the midg ut epithelium: basally located undifferentiated cells that give rise to the other two specialized cell types; secretory zymogen-like cells responsible for extracellular digestion and located mainly in the anterior midgut; and vacuolated cells, distributed all along the midgut and appearing to have s everal functions, including absorption, intracellular digestion, and nutrie nt transport. A single basic cell type forms the hindgut epithelium, The su ggested function for the hindgut is the transport and ejection of waste pro ducts. (C) 2000 Wiley-Liss, Inc.