Recognition of cattle skin by cercariae of Orientobilharzia turkestanica.

The cercariae of Orientobilharzia turkestanica attached to isolated cattle skin and penetrated it. The attachment was stimulated by warmth and by hydrophilic and lipophilic chemical cues of skin surface extracts. The enduring contact with the skin was also stimulated by the chemical cues, but not by warmth. Penetration of the cercariae into agar substrates was triggered by skin surface lipids, and free fatty acids were identified as the exclusively active compounds of the lipids. That the cercariae attach and remain on the skin by responding to at least two different chemical host cues is unique among the schistosomatids studied so far. It might reflect an adaptation to invade the hosts in clear water or near the water surface where chemical mud compounds will not interfere with host recognition.