Reconstruction of the feeding apparatus in Ploeotia costata (Euglenophyta)and its relationship to other euglenoid feeding apparatuses

The ultrastructure of the feeding apparatus in Ploeotia costata Farmer and Triemer was determined and compared to other euglenoid feeding apparatuses. The feeding apparatus opened subapically onto the ventral surface and exte nded nearly the entire length of the cell. It consisted of four parts at th e anterior surface: a comb, cytostome/pocket, vanes, and supporting rods. T he comb was a multilayered structure of three horizontal microtubular rows encased in cement and formed the dorsal lip of the apparatus. The cytostome /pocket was located between the comb and the supporting rods, tapered into the cell as the cytopharynx and was surrounded by five vanes, The electron- opaque vanes extended the entire length of the feeding apparatus and were l ined with microtubules for most of their length. Finally, two cement suppor ting rods that were joined by a crosspiece at the anterior end formed the v entral lip. The rods separated briefly before merging with the vanes. As th e merged rods and vanes descended into the cell, they gradually narrowed an d terminated, Comparisons of the feeding apparatus with Ploeotia vitrea, Di plonema ambulator, Lentomonas applanatum, and other euglenoids have led to the conclusion that the Type II feeding apparatus is found only in Ploeotia species.