Rectale Chloridepithelien und osmoregulatorische Salzaufnahme durch den Enddarm von Zygopteren und Anisopteren Libellenlarven

Abstract

The larvae of Coenagrion puella possess 3, and the larvae of Aeshna cyanea up to 486 rectal chloride epithelia which in both species are organized as transporting epithelia. Combined applications of the histochemical chloride precipitation technique, energy-dispersive micro-analysis of X-rays, autoradiography, and scintillation counting on A. cyanea revealed that the chloride epithelia adsorb chloride from the external solution. By use of radioactive sodium and chloride in hypotonic concentrations applied on normal and anus-sealed larvae it was demonstrated that the rectum of both species is the main pathway for salt uptake into the haemolymph. The stepwise increase in external osmolarity by the addition of mannitol results in a concomitant reduction of chloride uptake into the haemolymph. These results suggest that the rectal chloride epithelia are involved in hyperosmotic regulation by the absorption of salt from the external medium.