The flagellar development cycle of the uniflagellate Pelagomonas calceolata (Pelagophyceae)

Abstract

Vegetative cells of Pelagomonas calceolata Andersen & Saunders were confirmed to possess a reduced flagellar apparatus, consisting of a single basal body/flagellum that is not accompanied by either flagellar roots or a barren basal body. Just prior to division, the parental flagellum retracts (or is abscised) as two new basal bodies/flagella arise de novo. During cytokinesis the parental basal body segregates with a new basal body/flagellum, briefly producing a progeny cell typical of other known uniflagellates (i.e. containing a basal body/flagellum and accompanying barren basal body). The parental basal body then disintegrates or ''transforms'' out of existence, leaving both progeny cells with a single basal body/flagellum (i, e, neither progeny cell possesses any vestige of a mature flagellum/basal body). Pelagomonas calceolata belongs to a lineage of chromophyte algae characterized by having a reduced flagellar apparatus, but it is the only known species, not only in this lineage but among all eukaryotes, to have undergone the complete elimination of the mature flagellum/basal body.