Comparative ultrastructure of the cytoskeleton and nucleus of Distigma (euglenozoa)

Character evolution in heterotrophic euglenids

“…11) despite previous ultrastructural studies that did not report the presence of these structures (Yamaguchi and Anderson 1994;Angeler et al 1999). Moreover, our cladistic analysis of morphological characters grouped Distigma with the rhabdomonads (Fig.…”

“…17). We infer that sigmoidal strips like those found in D. proteus became increasingly flattened so that the arch and heel became more or less indistinguishable as in D. curvatum (Angeler et al 1999) (Fig. 17).…”

“…17). The frames began to thicken leaving a thin hook-like region that extended prearticularly beneath the overhang of an adjacent strip as in D. elegans and D. sennii (Angeler et al 1999). We suspect that these hook-like regions are homologous to the delicate structures marking the fused articulation zones (syn.…”

“…c. Distigma curvatum (Angeler et al 1999). d. Distigma elegans and D. sennii (Angeler et al 1999). e. Menoidium cultellus.…”

“…If these taxa are truly misplaced as small subunit rDNA sequences suggest (Müllner et al 2001), then they provide additional intermediate states between the biflagellated distigmids and the uniflagellated rhabdomonads. Detailed analyses of the pellicle of these "Astasia" taxa, particularly the value of P (the number of strip around the cell periphery) and W P (the number of whorls of strip reduction), will more confidently demonstrate their relationship to distigmids (Angeler 1998;Angeler et al 1999;Leander and Farmer 2000a); distigmids possess P = 18-20 and W P = 0, whereas Astasia (e.g., A. longa) possesses P = 40 and W P = 3 (Leander and Farmer 2000a).…”