Behavioral parasitology and perspectives on miracidial host-finding.

This paper proposes and outlines a new interdiscipline, 'behavioral parasitology,' and presents some interpretations in one of the leading themes of this field, miracidial chemosensitivity to snails. Controversies over miracidial attraction and species-specificity are considered from the standpoints of the distinction between taxis and kinesis, the need for a stimulus gradient, and the possibility of an early phase in a miracidium's behavior adapted for dispersal rather than host-finding. Some of the many possible organic stimulants are discussed with regard to quantitative production by snails, sensory thresholds of the parasites, and possible interaction with inorganic ions. Organic and inorganic stimulants are considered to possibly form qualitative as well as quantitative gradients. A thermodynamic interpretation of miracidial klinokinesis as a function of stimulant concentration suggests the existence of two or more separate types of receptors for the same stimulant, one with a higher affinity for the stimulant and mediating a weaker klinokinesis (possibly a long-range receptor as compared to the other.