Evidence of Zoophagy in a Second Liverwort Species, Pleurozia purpurea

The hepatic genera Colura and Pleurozia show trap-like structures in the water sacs of their leaves. The function of these structures usually has been interpreted as water storage, although zoophagy has also been suggested. The experimental evidence that a species of Colura was able to trap protozoa was presented some years ago. Therefore the trap-like structure in the water sacs of Pleurozia purpurea has been studied. It is described and illustrated by light and electron scanning microscopy. Feeding experiments revealed that the structures in the water sacs of Pleurozia purpurea are able to trap individuals of Blepharisma americana (Ciliata). This provides evidence that the lobules of this second hepatic genus function in zoophagy. Other experiments have shown that individuals of Blepharisma are attracted by plants of Pleurozia, although the exact reason for this behavior is not known. Observations in the field revealed a high percentage of lobules filled with various small animals and suggest that these are regularly trapped and not present by chance.