Scytonematopsis maxima Novis & Visnovsky, 2011

Novis, Phil M. & Visnovsky, Gabriel, 2011, Novel alpine algae from New Zealand: Cyanobacteria, Phytotaxa 22 (1), pp. 1-24 : 16-18

Scytonematopsis maxima Novis & Visnovsky , sp. nov. ( Figs 6A–G )

Trichomata matura isopolaria, uniseriata, cellulis 20–42 µm latis, 6–13 µm longis, semper brevioribus quam latioribus, contentis granularibus, ad parietes transversales constricta, ad terminos crescentes angustata. Cellulae terminales rotundatae. Heterocyta intercalaria spissamentis polaribus duobus praedita. Vagina mucilaginis aureo-fusca circum partes trichomatis maturas usque ad 6 µm crassa, circum partes juniores imprimis circum terminos crescents ad 1 µm crassa atque translucens. Ramificatio falsa binaria, primo per vaginam e flexu trichomatis in forma littera “U” exoriens inter heterocyta dissita, tum in paria ramulorum desinens. Thylacoides intra cytoplasma cellularum magnarum laxe dispositae. Hormogonia isopolaria, longitudine cellularum usque ad 19, per mortem cellularum et rupturam trichomatis parentalis generate. Trichomata in superficie agari prostrata, curva (raro cochleata). In cultura perlente crescens.

Type:— NEW ZEALAND. Westland : Mt Philistine, 1400 m, preserved cultured specimen from sample collected 30 November 2007, CHR610791 .

Mature trichomes isopolar and uniseriate, cells 20–42 µm wide, 6–13 µm long, always shorter than wide, contents granular, constricted at transverse walls, with some tapering at growing termini ( Figs 6A–C, F ). Terminal cells rounded; heterocytes intercalary, with two polar thickenings ( Fig. 6E ). Golden-brown mucilage sheath up to 6 µm thick around mature regions of trichomes, to 1 µm thick and translucent around younger regions, especially growing termini. False branching binary ( Fig. 6B, C ), starting from U-shaped loop of trichome emerging through sheath, occurring at some distance between heterocytes, resulting in pairs of branches. Thylakoids loosely arranged within cytoplasm of the large cells ( Fig. 6G ). Hormogonia isopolar, up to 19 cells long, generated through cell death and fragmentation from parental trichome ( Fig. 6D ). Trichomes prostrate and curved (rarely coiled) on agar surface ( Fig. 6A ). Very slow growing in culture.

Habitat:— Alpine herbfield soil, 1640 m, associated with scattered Chionochloa sp.

Distribution:— Mt Philistine, Arthur’s Pass National Park, New Zealand.

Etymology:— Named for its large size.

Observations:— Our analyses grouped Scytonema and Scytonematopsis with a strangely placed clade including a sequence from Microcoleus . It is well established that heterocytous cyanobacteria are monophyletic (e.g. Wilmotte 1994, Turner 1997, Wilmotte & Herdman 2001), so this result is clearly anomalous. There are two possible explanations: (1) that the sequences ascribed to Microcoleus and others are mistakenly identified; or (2) that our analysis is in error—perhaps through inappropriate model choice or outgrouping. Given the absence of support for the clade containing Scytonematopsis maxima by the Maximum Parsimony method, we speculate that the third is the likely explanation. Whether or not this is true, the branch lengths show that there is considerable genetic diversity within the organisms currently included in Scytonema , and the genus may be a candidate for further division. The inclusion of further representatives of the genus Scytonematopsis will likely help to resolve the relationship between the two genera.

Culture:— LCR-FBC.

Figures

FIGURE 6. Scytonematopsis maxima Novis & Visnovsky (photographed from culture LCR-FBC). A–F, light micrographs, G transmission electron micrograph. A. Appearance of trichomes on agar surface; arrows indicate developing hormogonia. B. Trichomes showing frequency of scytonematoid branching (arrows). C. Detail of a branch point showing exit through the sheath (s) and vacuolelike regions inside the cells (v). D. A hormogone being released from a parental trichome following necridic cell development (arrow). E. Growing hormogone showing isopolar development, rounded end cells (ec), slight tapering at growing ends, and heterocyte (h). F. Faster developing trichome in which tapered region (arrow) is much more obvious. G. Cells in longitudinal section showing transverse wall (tw), vacuole-like area (v) and irregularly arranged thylakoid membranes (tm). Scales: 1 mm in A, 50 µm in B, 10 µm in C, 50 µm in D (use for D–F), 0.5 µm in G.