Polysiphonia morrowii Harvey, 1857

Piñeiro-Corbeira, Cristina, Maggs, Christine A., Rindi, Fabio, Bunker, Francis, Baldock, Lin & Díaz-Tapia, Pilar, 2020, Molecular assessment of the tribes Streblocladieae and Polysiphonieae (Rhodomelaceae, Rhodophyta) in the British Isles reveals new records and species that require taxonomic revision, Cryptogamie, Algologie 20 (8), pp. 55-72 : 61-62

Polysiphonia morrowii Harvey

MOLECULAR IDENTIFICATION

In total, 51 rbc L sequences have been published for Polysiphonia morrowii including data from both regions where the species is considered native (eastern Asia) and introduced. Two new sequences have been obtained for specimens from the British Isles: one from Plymouth ( England) and one from Alderney (Channel Islands). Overall, the sequences available represent 14 rbc L haplotypes ( Fig. 2 ), with a sequence divergence of up to 0.5% (9 bp). The sequence from Plymouth was identical to specimens from western Asia, Australasia, Pacific and Atlantic South America and Atlantic France, while the sequence from Alderney represents a new haplotype. Polysiphonia morrowii was placed in the phylogeny in a highly supported clade with P. stricta , the generitype ( Fig. 2 ). The nearest neighbour of P. morrowii was P. pacifica ( AY958162 ) from which it diverged by 2.9-3.2%.

MORPHOLOGICAL OBSERVATIONS

Thalli forming tufts, up to 10 cm high, with interwoven prostrate axes and erect axes spirally branched mostly every five segments ( Fig. 6A, B ). Axes ecorticate and with four pericentral cells. Erect axes growing from sharply pointed apical cells ( Fig. 6C ), increasing to 40-65 µm in diameter in mid parts; segments 1.2-3.6 L/D. Trichoblasts not observed. Tetrasporangia formed in the last 2-3 branching orders in straight series ( Fig. 6D ), 20-30 µm in diameter. Sexual reproductive structures were not observed.

Figures

FIG. 2. — Phylogenetic tree estimated with ML analysis of rbcL sequences. Values at nodes indicate bootstrap support (BP) (only shown if ≥70). Species analysed in this study are grey-shaded and species or haplotypes found in the British Isles are in bold. For P. morrowii Harvey, the number (n) of sequences available for each haplotype is indicated. Codes for countries/regions: AD, Adriatic Sea; AR, Argentina; AUS, Australia; BC, British Columbia; CH, Chile; EN, England; FR, France; GUE, Guernsey; IR, Ireland; JA, Japan; KO, Korea; LG, Ligurian Sea; NZ, New Zealand; PO, Portugal; SP, Spain.

FIG. 6. — Polysiphonia morrowii Harvey: A, habit; B, upper part of an erect axis; C, apex of a branch with a pointed apical cell; D, young tetrasporangia in straight series. Scale bars: A, 10 mm; B, 100 µm; C, D, 50 µm.