Rhizophydiales Zoospore Types

Eighteen Ultrastructural Forms of Zoospores are Produced in this Order:

Our research has discovered 18 distinct zoospore forms in Rhizophydiales, each of which corresponds to a molecularly-based clade (Letcher et al. 2008b). 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.

Ultrastructural Characters and Character States in the Rhizophydiales (click here to see detailed illustrations of character states):

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 µm); 2=wide (~0.075 µm).

10. Close association of a lobe of a mitochondrion with kinetosome:

0=absent; 1=present.

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

Rhizophydium zoospores


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