[Studies on the hatching of miracidia of Dicrocoelium dendriticum (author's transl)]

The eggs of Dicrocoelium dendriticum were induced to open by solutions of formic acid and caproic acid (Table 1). The miracidia hatched in O2-free water after the eggs had been dried with N2 or in vacuum. The miracidia were able to live for 3 hours if water contained 20 mM NaCl, 10 mM KCl, and 1 mM CaCl2. Ca++-ions are obviously necessary for the mobility of miracidia. The experimental use of intestinal juice of the Roman snail Helix pomatia gave hatching results which were dependent on the absence of O2 (exposure to N2) and the presence of bacteria with a still unknown function. The dependence on pH seems to be indirect (Abb. 2). Studies on the permeabilities of the egg shell and the embryonic membrane ("vitelline membrane"), the evidence of an oligosaccharide (Abb. 3) liberated from the "spaltraum" (Abb. 1) during egg-opening, and the determination of the osmotic pressure of the hatching process (50% hatching in 1.2--14. Osmols sucrose/1000 ml H2O; Abb. 4) led to the following hypothesis of hatching mechanism: After the activation of the granular gland of the miracidium an enzyme is released into the extra-embryonic "spaltraum". A polysaccharide is digested to an oligosaccharide which cannot permeate the egg shell and the embryonic membrane. The rising osmotic pressure bursts off the operculum.