Variochloris pyrenoglobularis Novis & Visnovsky, 2012

Novis, Phil M. & Visnovsky, Gabriel, 2012, Novel alpine algae from New Zealand: Chlorophyta, Phytotaxa 39, pp. 1-30 : 22

Variochloris pyrenoglobularis Novis & Visnovsky , gen. et sp. nov. ( Figs 5A–F )

Cellulae quoad formam variabiles, sphaericae vel ellipsoideae vel pyriformes, 6.2–9.2 µm longae, 4.6–8.5 µm latae, cytoplasmate granulari, unicae vel in greges aggregatae. Chlorplastus viridis , cupulatus, parietalis, pyrenoidibus 1–2 per thylacoides valde circulariter flexuosae penetratis, quaeque pyrenoglobulis circumdatae. Autosporis 2–4 per sporangium regenerans. Variochloris sita per analysem per sequentias geneticas rbcL in clado valde confirmato conjunctim speciebus alpinis Stichococci novae-zelandiae, Raphidonemtae nivali ex USA atque speciebus duabus “Chlorellae”.

Type:— NEW ZEALAND: Westland : Mt Philistine, 1400 m, preserved cultured specimen from sample collected 30 November 2007, CHR610489 .

Cells variable in shape, spherical to ellipsoidal to pyriform, 6.2–9.2 µm long, 4.6–8.5 µm wide, with granular cytoplasm, single or in groups ( Fig. 5A, B ). Chloroplast green, cup-shaped, parietal, with 1–2 pyrenoids, penetrated by looped thylakoids, each surrounded by pyrenoglobuli ( Figs 5E, F ). Reproduction by autospores, 2–4 per sporangium ( Fig. 5C ). Analysis based on rbc L gene sequences placed Variochloris in a robustly supported clade with alpine species of Stichococcus from New Zealand, Raphidonema nivale Lagerheim from USA, and two “ Chlorella ” species ( Fig. 9 ). The same phylogenetic position was established with 18S rDNA sequences according to the Bayesian analysis, but no close matches were found with strains previously sequenced.

Habitat:— Alpine herbfield soil.

Distribution:— New Zealand.

Etymology:— Referring to variable shape and presence of pyrenoglobuli.

Observations:— Variochloris shares morphological features with Chlorella , but this generic name has priority in the Chlorellales (with the type species Chlorella vulgaris Beijerinck 1890 ). Pyrenoglobuli are known from taxa in other clades, such as Trebouxia ( Tarhanen et al. 2000) , and Heveochlorella hainangensis Zhang et al. (2008) in the Watanabea clade. Thylakoid patterns within the pyrenoid matrix in these taxa are also similar. The species of Stichococcus in the same clade as Variochloris do not have pyrenoids, and ultrastructure of this feature in Chlorella ellipsoidea Gerneck 1907 and C. saccharophila (Krüger) Migula 1907 appears to be unknown. The association of coccoid and non-coccoid species in this clade has been noted previously ( Novis et al. 2008), and these new results confirm the polyphyly of trebouxiophycean strains referred to Stichococcus.

Cultures:— LCR-CG2.

Figures

FIGURE 5. Variochloris pyrenoglobularis (photographed from culture LCR-CG2). A–D light micrographs, E, F, transmission electron micrographs. A. Large mature cells with granular contents and pyrenoids (pyr). B. Younger cells of smaller size, and autosporangia. C. Autosporangia (arrows) containing two and four daughter cells. D. A cell cluster including one cell with a dividing chloroplast (arrow), preliminary to cytokinesis. E. Sectioned autospores in sporangium, showing looped thylakoids (tm) intruding into pyrenoid matrix from periphery. F. Higher magnification view of pyrenoid matrix and starch plates (sp), showing pyrenoglobuli (pg) surrounding the thylakoid loops. Scales: 10 µm in A (use for A–D), 1 µm in E and F.

FIGURE 9. Phylogenetic analysis of a combined dataset representing the Chlorophyceae and Trebouxiophyceae inferred from rbcL gene sequences, with the third codon position omitted. Sequences contributed in this study are in bold. The tree typology is that inferred using MrBayes v3.0B4 (5 million generations). Numbers associated with nodes are Bayesian PP/MPB percentages (500 replicates). Scale bar represents 0.1 changes/site.