[Investigations on periodic phenomena in the snail Biomphalaria glabrata (author's transl)].

A method was developed to measure the locomotive activity of Biomphalaria glabrata over long periods of time. A snail, radioactively marked with a Co57-source, moves on a circular path. Beneath the experimental vessel a lead disc with a slit revolves (one revolution per minute) over a counter tube. Once every minute the amount of radioactivity emitted falls through the slit onto the counter tube. The position and thence the locomotive activity of the snail is determined from the intervals between the impulses. Under constant conditions the experiments show a distribution of crawling activity over the whole day that is the same for animals infected with Schistosoma mansoni and non-infected molluscs. The snails have more locomotive activity by day than by night, with a distinct maximum in the second hour after exposure to light. Experiments using food marked with I125-labelled fibrinogen revealed that feeding activity is three times as high at night as by day. The experiments also show that Biomphalaria glabrata tends to prefer night-time for egg laying. The results are compared with other known periodic phenomena in B. glabrata in a phase-chart.