Structural characterization of Eutreptia (Euglenophyta). II. The flagellar root system and putative vestigial cytopharynx

Abstract

The flagellar roots of Eutreptia pertyi Pringsheim and E. viridis Perty (Euglenophyta), considered to be primitive photosynthetic euglenophytes, are described. The arrangement and structure of the three roots are similar to those known for other euglenoids. A putative vestigial cytopharynx in the reservoir-canal transition region is similar to that reported in photosynthetic species of the order Euglenales; it is delimited by ventral flagellar root microtubules that are associated in the mid-distal canal region with a striated fibril, reported here for the first time in euglenoids. If the number of emergent flagella was reduced from two to one during the evolution of the euglenoids, then the presence of a vestigial cytopharynx, together with flagellar reduction, suggests that the Eutreptiales may have arisen prior to the Euglenales but subsequent to the Heteronematales.