Glaucophytes are a kingdom-scale lineage of unicellular algae with uniquely underived plastids. The genus Cyanophora is of particular interest because it is the only glaucophyte that is a flagellate throughout its life cycle, making its morphology more directly comparable than other glaucophytes to other eukaryote flagellates. The ultrastructure of Cyanophora has already been studied, primarily in the 1960s and 1970s. However, the usefulness of that work has been undermined by its own limitations, subsequent misinterpretations, and a recent taxonomic revision of the genus. For example, Cyanophora's microtubular roots have been widely reported as cruciate, with rotationally symmetrical wide and thin roots, although the first ultrastructural work described it as having three wide and one narrow root. We examine Cyanophora cuspidata using scanning and transmission electron microscopy, and construct a model of its cytoskeleton using serial-section TEM. We confirm the earlier model, with asymmetric roots. We describe previously unknown and unsuspected features of its microtubular roots, including (i) a rearrangement of individual microtubules within the posterior right root, (ii) a splitting of the posterior left root into two subroots, and (iii) the convergence and termination of the narrow roots against wider ones in both the anterior and posterior subsystems of the flagellar apparatus. We also describe a large complement of nonmicrotubular components of the cytoskeleton, including a substantial connective between the posterior right root and the anterior basal body. Our work should serve as the starting point for a re-examination of both internal glaucophyte diversity and morphological evolution in eukaryotes.
Bibliographical noteFunding Information:
We thank Henry Towbin of the AMNH Microscopy and Imaging Facility, for help with operation of the electron microscopes, and Bryan Kao, for assisting with image alignments and scaling for computer modeling. We thank the participants of AMNH’s 2014 Scientific Imaging course for assistance with the SEM preparation. This work was supported by the Gerstner Scholars Program, the Lerner-Gray Fund, and the AMNH REU Biology Program.
© 2017 Phycological Society of America
- Cyanophora paradoxa
- basal apparatus
- transmission electron microscope