In situ degradation of cellulose fibres by the entodiniomorph rumen ciliatePolyplastron multivesiculatum

Summary The feeding behaviour of the rumen ciliatePolyplastron multivesiculatum has been studied with scanning and transmission electron microscopy. In contrast to other large entodiniomorphs,Polyplastron scarcely attaches to plant substrata such as straw or alfalfa; however, it readily phagocytes cellulose fibres (like epidermal bristles of alfalfa) suspended in the rumen fluid.The different stages of ingestion and intracellular degradation of this particular substrate are described at the ultrastructural level.Engulfment involves active movements of the vestibular lips. The digestion follows a peculiar pattern (permeative way): the cellulose substrate is gradually decomposed in situ inside the primary digestive vacuole without large fragmentation or pinching off of small vesicles. Thus degradation products are not stored in secondary vesicular systems as they are for other plant substrates (cytotic way).Thus, there is no single or general pattern of cellulosic structures lysis in entodiniomorph rumen ciliates. Rather, several pathways can be observed, probably according to the nature of the ingested plant material.