Phormidium arthurensis Novis & Visnovsky, 2011

Novis, Phil M. & Visnovsky, Gabriel, 2011, Novel alpine algae from New Zealand: Cyanobacteria, Phytotaxa 22 (1), pp. 1-24 : 19-20

Phormidium arthurensis Novis & Visnovsky , sp. nov. ( Figs 7G–M )

Trichomata isopolaria uniseriata, plerumque solitaria vel faciliter dissociata, cellulis 3–4 µm lata, 2–5 µm longa, brevioria quam latioria vel circa isodiametrica, ad parietes transversales subconstricta. Non motiles. Trichomata stricta vel subcurva. Cellulae terminales rotundatae. Vagina tenuis pellucidaque , trichomata solitaria continens. Ramificatio nulla. Regeneratio trichomatis per fragorem in hormogonia intra quae trichoma tota interdum in segmenta ex 2–4 cellulis composita fractum est. Cellulae necridicae non visae. Thylakoides uniformiter compaginatae peripheralesque.

Type:— NEW ZEALAND. Westland : Mt Philistine, 1400 m, preserved cultured specimen from sample collected 30 November 2007, CHR610795 .

Trichomes isopolar and uniseriate, generally solitary or easily dissociated, cells 3–4 µm wide, 2–5 µm long, shorter than wide to approximately isodiametric, slightly constricted at transverse walls ( Fig. 7G ). Nonmotile. Trichomes straight to slightly curved. Terminal cells rounded. Sheath thin and translucent, containing solitary trichomes. Branching absent. Trichome reproduction through fragmentation into hormogonia, in which whole trichome may break into segments of 2–4 cells ( Figs 7G, I, J ); necridic cells not observed. Thylakoids evenly stacked and peripheral ( Figs 7L, M ).

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

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

Etymology:— For Arthur’s Pass National Park, the collection site.

Observations:— At least 8 morphological groups of Phormidium are recognised ( Komárek & Anagnostidis 2005); of these, P. murrayi and P. arthurensis belong to a group with cylindrical trichomes having widely rounded apical cells and lacking attenuation and calyptrae. Phormidium molle and P. priestlyii ( Fritsch 1917) also belong to this group, but have recently been transferred to the genus Phormidesmis, based partly on the results of molecular analysis ( Komárek et al. 2009). Phormidium murrayi and P. arthurensis , however, are not closely related to either of these former species of Phormidium ( Taton et al. 2006) ; nor are they close to the P. autumnale cluster which is taken to represent Phormidium sensu stricto ( Fig. 3 ; Komárek et al. 2009). It is therefore also a candidate for new generic status. However, their relationship to Coleofasciculus is still uncertain. Although our analyses including single representatives of Coleofasciculus and Symploca appear to resolve a sister group relationship with the P. murrayi / P. arthurensis clade, this support is absent in analyses including more Coleofasciculus representatives and different outgroups ( Siegesmund et al. 2008). We therefore favour awaiting more data before making such a change. The other New Zealand strains CYN38 and CYN39 from Red Hills Tarn ( Heath et al. 2010) represent a close relative: there are 10 base differences between P. arthurensis and CYN38 over the 372 bp of the latter sequence. However information on the intergenic spacer of these strains is still lacking, and it is this that distinguishes P. arthurensis from P. murrayi .

Culture:— LCR-OSC4a.

Figures

FIGURE 3. Phylogenetic analysis of selected Oscillatoriales inferred from 16S 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); these are shown only when PP> 0.94. Scale bar represents 0.1 changes per site.

FIGURE 7. A–F. Hormoscilla irregularis Novis & Visnovsky (photographed from culture LCR-OSC2; light micrographs). A. Long trichome showing short cells with constrictions between them. B. Typical morphology with arrangement of trichomes into segments of cells, with irregular lateral position. C. Trichomes become truncated by fragmentation and dissolving of the sheath. D. False branching through trichome fragmentation (during which necridic cells occur, as indicated by arrow). E. False branching by trichome overlap. F. Release of hormogonia. G–M. Phormidium arthurensis Novis & Visnovsky (photographed from culture LCR-OSC4, G–K light micrographs, L–M transmission electron micrographs). G. Mature trichome with rounded end cell, and arrangement into cell segments (arrows between the segments). H. Trichome with fragmented end, in which the sheath is visible (arrow). I. Prior to fragmentation, the cell segments become pronounced. J. A hormogone released from this fragmentation. K. Development of the new trichome (arrow) is isopolar. L, M. Cells in transverse section showing sheath (s) and thylakoid membranes (tm), which are peripheral and tightly packed, and may be somewhat curved (M). Scales: 10 µm in F (use in A–K), 1 µm in L (use in L–M).