PHYLOGENY OF DIPLONEMA-AMBULATOR (LARSEN AND PATTERSON) .2. HOMOLOGIES OF THE FEEDING APPARATUS

The ultrastructure of the feeding apparatus in Diplonema ambulator was determined and compared to other euglenozoan feeding apparatuses. A c ytostome opens to the right of the flagellar pecker and continues prox imally into the cell as a tubular cytopharynx. Paralleling the cytopha rynx on the side facing the flagellar pocket are five vanes and a cyto pharynx-associated matrix (CAM). A complex electron-dense structure su rrounds the cytostome/cytopharynx, vanes, and CAM. An extension of thi s structure gives rise to a large band of microtubules that parallels the cytopharynx. The structure divides into a series of thin matrices which are supported by three microtubular bundles. The feeding apparat us is connected to the flagellar pocket by an anterior cytoplasmic loo p that is supported by several microtubules, some of which are embedde d in a dense matrix and eventually develop into vanes. On the flagella r pocket side, the microtubules are joined by another band of microtub ules and continue to line the flagellar pocket as it extends into the cell. These results suggest that the feeding apparatus and flagellar p ocket extension in Diplonema ambulator may represent a single, highly modified bodonid-like feeding apparatus, contradicting an earlier idea that Diplonema has two separate feeding apparatuses.