Electron microscopy reveals features that are used to characterize orders and families
- Research has discovered 18 distinct zoospore subtypes in Rhizophydiales, each of which corresponds to a molecularly-based clade.
- Each zoospore form in Rhizophydiales is defined on the basis of having a unique suite of ultrastructural character states (listed below). We analyze these characters and look for concordance with gene-based phylogenetic hypotheses to delineate taxa.
- Taxa are charactererized by having unique suites of character states. Thus, the series of numbers under the illustration of each type of zoospore is like a numerical bar-code for a taxa. See interactive key to taxa based on zoospore ultrastructural character states.
Illustrated ultrastructural characters
and character states
(Click the character number to see illustrations of character states for each character)
1. Microbody-lipid globule cisterna: 0=absent; 1=simple;
2=inconspicuously fenestrated; 3=conspicuously fenestrated.
2. Kinetosome-associated structure:
0=absent; 1=a solid spur; 2=a laminated spur; 3=a shield.
3. Number of lipid globules: 0=predominantly one; 1=multiple.
4. Vesiculated region adjacent to kinetosome: 0=absent; 1=present.
5. Fibrillar bridge between kinetosome and non-flagellated centriole: 0=perpendicular to the two structures; 1=diagonal between the two structures.
6. Microtubular root: 0=absent; 1=present.
7. Number of mitochondria in longitudinal section: 0=one; 1=multiple.
8. Granular cylinder in core of kinetosome and/or non-flagellated centriole: 0=absent; 1=present.
9. Perpendicular zone of convergence in fibrillar bridge between kinetosome and non-flagellated centriole: 0=absent; 1=narrow (0.010-0.025 micrometers);
2=wide (approximately 0.075 micrometers; greater than 0.025 micrometers).
10. Close association of a lobe of a mitochondrion with kinetosome:
11. Close association of a lobe of a microbody with kinetosome:
0=absent; 1 = present
12. Location of nucleus:
0-outside the ribosomal mass;
1=embedded in the ribosomal mass.
13. Microbody morphology: 0=simple; 1=lobed.
14. Endoplasmic reticulum ramifying through the ribosomal mass:
0=absent; 1 = present