DESCRIPTION OF THE PHYLUM CYANIDIOPHYTA (SAUNDERS AND HOMMERSAND 2004)

EUKARYA> ARCHAEPLASTIDA> RHODOPLANTAE> CYANIDIOPHYTA

Cyanidiophyta (si-a-ni-de-O-fa-ta) is derived from two Greek roots that mean dark blue (kuanos -κυανός); and plant (phyto -φυτό). The reference is to the bluish caste created by the phycobillins in the chloroplast.

INTRODUCTION TO THE CYANIDIOPHYTA These are small coccoid unicellular organisms that have a distinctive blue-green appearance (Figure 1). They are unusual among eukaryotes in that they are obligate extremeophiles (they require 50-55C and pH (0.5) 3-5; Ciniglia et al. 2004) and occur in hot springs, acid rivers and deep ocean vents (Figure 2). They may be more common, but their simple Porphyridium-like appearance makes them hard to identify. Presently, they are made up of only three genera (Cyanidium, Cyanidioschyzon, and Galdiera), but extremely high levels of molecular diversity suggests that they may be separated into many more taxa. We elect to follow the taxonomic system of Saunders and Hommersand (2004; see Figure 3) who have attempted to rectify the past problems with rhodophyte classification systems by application of molecular phylogenetics. Their system separates the taxa of the “Cyanidiales” into a sister phylum based on molecular evidence that consistently separates them as a sister group to the rest of the “red algae” (Gross et al. 2001; Ciniglia et al. 2004; Yoon et al. 2002; Muller et al. 2001; Saunders and Hommersand 2004). Ciniglia et al. (2004) and Saunders and Hommersand (2004) have identified the following ultrastructural synapomorphies: golgi associated with endoplasmic reticulum, cell walls that are thick and proteinaceous, production of endospores, heterotrophic ability.

FIGURE 1. Coccoid cells of Cyanidium. Image from http://microscope.mbl.edu/baypaul/microscope/images/t_imgAZ/cyanidium11_ypw.jpg	FIGURE 2. A plate with a TEM micrograph of a Galdieria cell and five hot spring locations where it was collected. Image from http://www.biology.uiowa.edu/debweb/html/ThermoacidophilicCyanidiales.php

FIGURE 3. Major Clades of the Rhodoplantae. This cladogram is a modification of Saunders and Hommersand (2004), Doweld (2001), Gross et al. (2001), Ciniglia et al. (2004), Yoon et al. (2002), Muller et al. (2001), and Cavalier-Smith (1981, 1998).

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By Jack R. Holt. Last revised: 03/16/2013