Pegethrix convoluta Mai, Johansen et Bohunická, 2018

Mai, Truc, Johansen, Jeffrey R., Pietrasiak, Nicole, Bohunická, Markéta & Martin, Michael P., 2018, Revision of the Synechococcales (Cyanobacteria) through recognition of four families including Oculatellaceae fam. nov. and Trichocoleaceae fam. nov. and six new genera containing 14 species, Phytotaxa 365 (1), pp. 1-59 : 22-24

Pegethrix convoluta Mai, Johansen et Bohunická sp. nov.

Diagnosis: ―Differing from other species in the genus based on the frequent formation of loose irregular nodules. Distinguishable from P. indistincta in the cytosine residue opposite the basal 3’ unilateral bulge of the D1-D1’ helix ( Figs. 6c, d ) and the V3 helix sequence and structure ( Figs. 9c, d ). Some similarity with P. bostrychoides and P. olivacea in nucleotides 1–15 on the 5’ strand and their complement was observed, but the absence of the V2 helix and other dissimilarities clearly set them apart.

Description:— Colony bright blue green, radially spreading, growing into the agar. Filaments fasciculated, long, sometimes singly or doubly false branched ( Fig. 12a ), straight or slightly bent ( Figs. 12a–b, e ), frequently forming loose to compact nodules ( Figs. 12b–c ), 1.4–3.9–(4.9) μm wide. Sheath firm, colorless, usually attached to trichome ( Fig. 12e ), occasionally widened ( Figs. 12d–e ), rarely irregular and stratified, up to 1.3 μm wide. Trichomes untapered, not or slightly constricted at distinctly visible cross-walls, with necridia ( Figs. 12b, e–f ), lacking meristematic zones, with cell division occurring throughout trichome, 1.3–2.5 (3.2) μm wide. Hormogonia few-celled ( Fig. 12a ). Cells slightly shorter than wide to longer than wide, sometimes with a single central granule, with parietal thylakoids, 1.0–2.5–(3.7) μm long. End cells rounded.

D1-D1’ helix of the 16S–23S ITS region 91 nucleotides long, with basal 3’ side loop of 9 unpaired nucleotides (5’- ACAUCCCAA-3’) opposed by a single cytosine residue, with multiple small internal loops at position 14–15/69–70 (with sequence 5’-AG/GA-3’), at 26–27/56–57 and 32–33/50–51, one large asymmetrical internal loop at position 19–23/60–65. Terminal loop with 4 nucleotides, with sequence 5’-GAGA-3’ ( Fig. 6c ). No V2 helix present between tRNAAla and tRNAIle. Box B helix with 36 nucleotides, bearing 6 nucleotides at terminal loop ( Fig. 7c ). V3 helix 110 nucleotides long, with one basal internal loop (5–6/101), one unilateral bulge at positions 12–14, several small internal loops at positions 27–29/81–83, 32–33/76–77, 39–41/68–71 and 45–48/61–64 and a pair of mismatched 5’-U/C-3’ at position 36/74. Terminal loop of 6 nucleotides, having sequences 5’-GUAAAA-3’ ( Fig. 9c ).

Etymology:— convoluta (L.): rolled up; referring to the nodules in the trichomes.

Type locality: ―Lower Calf Creek Falls site, Grand Staircase-Escalante National Monument, 37°49’44.77’’N, 111°25’12.58”W, collected on 15 August 2006 by Markéta Bohunická. Large seep wall and waterfall in Navajo Sandstone, in the GSENM, Kane County, Utah, USA. Small pool with blackened soil and microbial layer at the base of seep wall.

Holotype here designated:— BRY37773 !, Herbarium for Nonvascular Cryptogams, Monte L. Bean Museum, Provo, Utah.

Reference strain: ―GSE-PSE-MK38-07D, Algal Culture Collection at John Carroll University, Cleveland, USA. Other reference strain of the species: GSE-PSE-MK22-07D, Algal Culture Collection at John Carroll University, Cleveland, USA.

Taxonomic notes:— Based on the ecological preference for subaerophytic environments, morphological traits such as the absence of constrictions at cross-walls, attached sheaths, and rounded apical cells, this species keys to several possible species in Leptolyngbya , including Leptolyngbya “Albertano/Kováčik-green” 1992, L. compacta (Kützing ex Hansgirg 1892b: 88) Komárek in Anagnostidis (2001: 374), L. subtilissima (Kützing ex Hansgirg 1892b: 87) Komárek in Anagnostidis (2001: 374), and L. schmidlei ( Limanowska 1912: 364) Anagnostidis & Komárek (1988: 392) . The closest morphospecies using both morphological and ecological criteria is L. compacta . Compared to L. compacta and L. subtilissima , P. convoluta has larger trichome width, and isodiametric to shorter than wide cells compared to the isodiametric to longer than wide cells in those two species. Trichomes of L. schmidlei have average width larger than P. convoluta . L. compacta , L. subtilissima and L. schmidlei are poorly understood species based on the absence of illustrations in the original diagnoses and later accounts ( Komárek & Anagnostidis 2005), and so these names should likely be avoided in modern taxonomic treatments. We conclude that this species has not been described before in any other genus, and represents a new species to science.

P. convoluta is morphologically similar to P. olivacea , but differs in trichome color and in the sequence of the 16S-23S ITS region (percent dissimilarity = 8.23%, see Table 8). It is molecularly most similar to P. indistincta , with highly similar secondary structures (identical in the Box B helix) and fairly low percent dissimilarity between ITS sequences. Percent dissimilarity between P. convoluta and P. indistincta is intermediate between levels normally separating species and populations of the same species (4.11%, see Table 8). The trichome widths overlap, although P. indistincta typically has wider trichomes than P. convoluta .

Figures

FIGURE 6. D1-D1’ stems of species described in Oculatellaceae.The stem structures of genera described previously in other publications (Oculatella, Thermoleptolyngbya, Timaviella) or in publications under provision (Trichotorquatus) are not shown here.

FIGURE 7. Box B helices of species described in Oculatellaceae. The structures of genera described previously in other publications (Oculatella, Thermoleptolyngbya, Timaviella) or in publications under provision (Trichotorquatus) are not shown here.

FIGURE 9. V3 helices of species described in Oculatellaceae. All species described have this structure. The V3 helix of Cartusia aeruginosa is missing because we do not have the full length of its ITS region.

FIGURE 12. Pegethrix convoluta. A. Consecutively false-branching filaments. B–C. Compact nodules formed by rapid cell division in local region of trichomes. D–E. Sheath rarely irregular and stratified, more commonly tightly attached to trichomes. F. Necridia abundant in mature trichomes. Scale bar 10μm in 1000X magnification.