Fine structure and function of the rectal chloride epithelia of damselfly larvae

Abstract

Zygopterous larvae posses three epithelial pads in the rectum which show the fine structural organization of ion transporting epithelia. They are directly exposed of the external medium, which is ventilated through the anus. The ventilation frequency is related to the external salinity. Adaptation to highly hypotonic salt solution (10 μM NaCl) leads to a high ventilation activity. Histochemical precipitation of chloride results in dense silver chloride deposits specifically lining the lumen side of the epithelia. These results suggest that the rectal chloride epithelia are involved in osmotic hyperregulation by the absorption of electrolytes.