Diclidophora merlangi: Sloughing and renewal of hematin cells

Electron microscopy and section autoradiography have been used in an attempt to find evidence of sloughing and renewal of hematin (digestive) cells in the gut of Diclidophora merlangi. Hematin cells are connected by septate desmosomes to a polymorphic, syncytial connecting tissue which supports and protects each cell from stresses imposed on the gut by body movements. The sloughing of hematin cells occurs only rarely, and evidence of the event is restricted to the occasional finding of a free and relatively undamaged cell in the lumen of the main ceca. The connecting syncytium of the main ceca leading to the foregut is attenuated and, in places, perforated by small pores. Small, undifferentiated cells can be found below the pores, and some of these cells may represent embryonic gut cells. Immature hematin cells, without pigment or Golgi stacks, border the lumen in this region of the gut and are connected to the syncytium by septate desmosomes. Pulse-chase experiments with tritiated thymidine indicate that any renewal of hematin cells takes place a a very low rate.