Behavioral Responses of Miracidia of Schistosoma mansoni and Other Trematodes to Substances Emitted by Snails

An experimental system, based on the mass reaction of miracidia to the "point-inoculation" of test materials in small wells, was devised to study miracidial behavior in the absence of snails. These studies disclosed that Biomphalaria glabrata and a variety of unrelated snails naturally emit some substance(s) capable of altering the behavior of miracidia of Schistosoma mansoni and of certain other trematodes in a distinctive manner. In general, the miracidial response appears to be nonspecific as to the source of the stimulant or the species of miracidium responding. Aquatic invertebrates other than snails do not seem to represent important sources of stimulant. The behavior of stimulated miracidia in the experimental system resembles that exhibited by some miracidia in the vicinity of a snail and suggests chemokinesis rather than chemotaxis. The miracidial stimulant emitted by B. glabrata is thermostable, retains its activity during prolonged storage, has a mol wt