Tolypothrix pseudorexia Novis & Visnovsky, 2011

Novis, Phil M. & Visnovsky, Gabriel, 2011, Novel alpine algae from New Zealand: Cyanobacteria, Phytotaxa 22 (1), pp. 1-24 : 14-16

Tolypothrix pseudorexia Novis & Visnovsky , sp. nov. ( Figs 5A–N )

Trichomata heteropolaria uniseriata, cellulis 10–20 µm latis, 2–7 µm longis, semper brevioribus quam latioribus, materia contenta grandulari, ad parietes transversales subconstricta. Heterocyta plerumque ad basibus ramorum atque hormogoniorum, interdum in paribus intercalaribus disposita, parte parietis singulari polari incrassata. Vagina pallide brunnea , 1–2 µm crassa. Post divisionem trichomatum ad heterocyta lateraliter pseudoramificans. Thylakoides peripherales sed interdum ad centrum cellulae implicatae. Hormogonia primo progressu isopolari, deinde heteropolari post progressum heterocyti ad terminum alterum ex quo crescentia tunc terminata est; hic terminus saepe ad trichoma aliud per pulvillum mucilaginosum connectens, pseudoramum prolongentem saepe angulo recto divergentem formans. Trichomata varie in superficie agari prostrata atque erecta .

Type:— NEW ZEALAND. Westland : Mt Philistine, 1400 m, preserved cultured specimen from sample collected 30 November 2007, CHR610792 .

Trichomes heteropolar and uniseriate, cells 10–20 µm wide, 2–7 µm long, always shorter than wide, contents granular, slightly constricted at transverse walls ( Fig. 5B–L ). Heterocytes usually at bases of branches and hormogonia ( Fig. 5B–D, H ), occasionally in intercalary pairs ( Fig. 5F ), with single polar wall thickening. Light brown sheath, 1–2 µm thick. False branching lateral, occurring after trichome division at heterocytes ( Fig. 5B, E ). Thylakoids peripheral, but may be infolded towards cell centre ( Fig. 5N ). Hormogonia with isopolar development initially ( Fig. 5G ), becoming heteropolar following the development of a heterocyte at one end ( Fig. 5H ), from which growth then ceases ( Fig. 5I ); this end often attaches to another trichome via a mucilage pad to form a lengthening pseudobranch, often at a right angle ( Figs 5K, L ). Trichomes variously prostrate and erect on agar surface ( Fig. 5A ).

Habitat:— Aerophytic crust on greywacke rock surface, 1640 m, associated with alpine Trentepohlia sp.

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

Etymology:— Resembling the genus Rexia .

Observations:— Erect trichomes are unusual in Tolypothrix , more resembling the species Rexia erecta ( Casamatta et al. 2006) , and suggestive of adaptation to an aerophytic habitat. However, the hormogonia of Rexia can divide in two planes; exhaustive searching of T. pseudorexia failed to establish the occurrence of this feature. The 16S–23S intergenic spacer sequence also differs somewhat from that of Rexia (although differences with published Tolypothrix species are also present). 16S rDNA data were not obtained. However, we also note that this part of the 16S rDNA phylogeny has not been well resolved in the past ( Casamatta et al. 2006).

Culture:— LCR-CYTR.

Figures

FIGURE 5. Tolypothrix pseudorexia Novis & Visnovsky (photographed from culture LCR-CYTR). A–L light micrographs, M–N transmission electron micrographs. A. Profile of colony on agar, showing erect trichomes (arrow). B. Typical false branch arising from a heterocyte (arrow) with single pore. C. Adjacent false branches (arrows) giving the superficial appearance of scytonematoid structure. D. False branches are often seen to form right angles; these may be the result of hormogone adhesion rather than trichome division. E. On 10% BG-11 medium the heterocytes (h) are often reduced, but still evident at the branch points. F. Adjacent intercalary heterocytes preceding trichome division (arrow). G. Development is isopolar in young hormogonia. H. A heterocyte develops at one end (arrow) and this end widens. I. Growth continues from the other end of the hormogonium (arrow). J. The heterocytous end of the hormogone possesses a mucilage pad (arrow). K. This pad frequently adheres to another trichome. L. Growth from the adhered trichomes leads to a network of branches, potentially explaining the profile of the colony in A. M. Cells in longitudinal section showing layered sheath (s) and lighter central area (ca). N. Cell in transverse section showing peripheral infolded thylakoid membranes (tm), which are not widened. Scales: 0.5 mm in A, 50 µm in E (use for B–L), 1 µm in M (use for M–N).