Chlamydomonas palmellomoewusii Novis & Visnovsky, 2012

Novis, Phil M. & Visnovsky, Gabriel, 2012, Novel alpine algae from New Zealand: Chlorophyta, Phytotaxa 39, pp. 1-30 : 14

Chlamydomonas palmellomoewusii Novis & Visnovsky , sp. nov. ( Figs 1A–D )

Cellulae juvenes ellipsoideo-cylindricae, 10.8–11.6 µm longae, 4.6–5.8 µm latae, flagellis 2 circa aequilongis praeditae. Papilla bimamillata, ex apice cellulari subexcentrica. Aetate cellulae maiores, ellipsoideae, papillas flagellaque amittentes. Cellulae maturae in cultura liquida crescentes usque ad 13.1 µm longae, 10.8 µm latae; in agaro, in statu palmelloideo usque 18.0 µm longae, 15.4 µm latae attingentes. Chloroplastus viridis , parietalis, cupulatus, incisuris numerosis praeditus, pyrenoide unica centraliter posita, intrusiones irregulares multiplices e membranis thylacoidium compositae eae lamellis amylaceis circumdatae continens. Vacuolae apicales contractiles duae. Stigma ellipsoideum , in parte cellulae 1/3 apicali situm. Zoosporis 2–4–8 per sporangium regenerans.

Type:— NEW ZEALAND: Westland : Mt Philistine, 1400 m, preserved cultured specimen from sample collected 30 November 2007, CHR610484 .

Young cells ellipsoidal–cylindrical, 10.8–11.6 µm long, 4.6–5.8 µm wide, with 2 flagella of approximately equal length. Papilla bimammillate, slightly offset from cell apex. Cells becoming larger and ellipsoidal with age, with papilla and flagella being lost ( Fig. 1A ). Mature cells in liquid culture up to 13.1 µm long, 10.8 µm wide; on agar, up to 18.0 µm long, 15.4 µm wide in palmelloid state ( Fig. 1B ). Chloroplast green, parietal, cup-shaped with numerous incisions, with single, centrally located pyrenoid, containing multiple irregular intrusions of thylakoid membranes and surrounded by starch plates ( Fig. 1C, D ). Two apical contractile vacuoles. Stigma ellipsoidal, located in apical third of cell ( Fig. 1A ). Reproduction by zoospores, 2–4–8(–16) per sporangium ( Fig. 1B ). DNA sequence data for both 18S ( Fig. 7 ) and rbc L ( Fig. 9 ) show that C. palmellomoewusii belongs to the Moewusii clade.

Habitat:— Alpine herbfield soil.

Distribution:— New Zealand.

Etymology:— Reflecting the strong resemblance of the species to the related C. moewusii Gerloff 1940 , and occurring predominantly in a palmelloid form in culture.

Observations:— Data for the rbc L gene ( Fig. 9 ) show that this species is quite distinct from C. pseudogloeogama , previously found on Mt Philistine ( Novis et al. 2008); the two are not sister species. They also differ in size, length:width ratio, papilla structure, and in the more cylindrical shape of the young cells in C. palmellomoewusii . In this respect, and in papilla structure, cell size, and pyrenoid location, the new species strongly resembles C. moewusii ; in the absence of molecular data, the specimens would likely have been assigned to this species. Morphology of the pyrenoid is characteristic of the Moewusii clade.

According to traditional classification, this strain would belong in section Chlamydella (Ettl 1983), due to its single lateral pyrenoid in a cup-shaped chloroplast. Within this section it is closest to C. gymnogama ( Deason 1967) , which also has numerous incisions in the chloroplast. C. gymnogama is regarded as a synonym of Lobochlamys segnis ( Pröschold et al. 2001) , which 18S sequences show to differ from C. palmellomoewusii .

Cultures:— LCR-CG1, LCR-CG4.

Figures

FIGURE 1. Chlamydomonas palmellomoewusii (photographed from culture LCR-CG1). A, B light micrographs, C, D transmission electron micrographs. A. Young (y) and mature (m) cells, showing their inflation and increased rounding with age. The pyrenoid (pyr) and one contractile vacuole (cv) are indicated in one cell, the bimammillate papilla (bp) in another, and the stigma (s) in a third. B. Typical palmelloid form in older agarised cultures, with large mature cells and zoosporangia. C. Section of zoospores in a sporangium, showing incised parietal chloroplast (pc) containing starch (st), and large single pyrenoids (pyr) surrounded by starch plates (sp). D. Higher magnification view of pyrenoid matrix surrounded by starch plates (sp), showing irregular intrusions of thylakoid membranes (tm) in the matrix. Scales: 10 µm in B (use for A and B) and 1 µm in C and D.

FIGURE 7. Phylogenetic analysis of the Chlorophyceae inferred from 18S rDNA sequences. 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.

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.