[Influence of CO2 and pH on the attachment response of the cercaria of Diplostomum spathaceum (trematoda) (author's transl)].

1. The attachment of the cercaria to artificial substrates (offered via dialyzing membranes) in definite media was investigated under conditions of variable pH and [CO2]. 2. A decrease of the pH of the substrate releases only attachments in CO2 containing media and consequently acts via CO2 systems of the medium. 3. As effective components of CO2 systems, dissolved CO2 + H2CO3 are confirmed. 4. The sensitivity of the reaction on gradients of the CO2 partial pressure (in solution) could be established by offering substrates with lowered pH in CO2 containing media. Thus, by raising the CO2 partial pressure from ca. 0,04% to 0,15% maximal fixation rates were obtained (Fig. 3). 5. The carboanhydrase inhibitor acetazolamide, when added to the medium, had no direct influence on the CO2 receptors.