AN ULTRASTRUCTURAL-STUDY OF LENTOMONAS-APPLANATUM (PREISIG) N-G (EUGLENIDA)

Lentomonas applanatum (syn. Entosiphon applanatum Preisig) is a biflag ellate, phagotrophic euglenid found in intertidal salt marshes. Lentom onas applanatum bears a superficial similarity to Entosiphon sulcatum, however, an ultrastructural study of L. applanatum revealed many feat ures that are atypical for other described species of the genus Entosi phon. These features include number and organization of pellicular str ips, construction of the feeding apparatus, nature of the flagellar tr ansition zone and flagellar apparatus, and point of flagellar emergenc e. These differences show that L. applanatum is related more closely t o phagotrophic genera such as Ploeotia than to E. sulcatum. The constr uction of the feeding apparatus and pellicle suggest that L. applanatu m has retained many of the pleisiomorphic characters that were present in the earliest euglenids. The presence of similar structures in othe r related protists may provide important clues as To the evolution of the Euglenida.