Polysiphonia stricta (Dillwyn) Greville (Ar/A) (Genetic group 3)

Plants straw-yellow below transitioning to light red at the tips, or bright, brownish or blackish red throughout. Forming tufts or carpets, 5-12 cm high (Feature image above). Branching sparse below, more regularly alternate above with the tips at times appearing tufted (Image A). Basal system an extensive tangle of prostrate filaments anchored by rhizoids with an open connection to the bearing cell (Image B). Polysiphonous construction with the apical cell rounded (Image C) and four pericentral cells, which can twist in some segments to present a distinctive pattern (Image D). Ecorticate throughout, prostrate axes 70-120 µm wide with the segments roughly square (length equals width) while erect axes are ~50 µm wide at the tips widening to 120 µm in mature axes with the segments 2.5 to as much as 12X longer than wide (Image D). Some individuals produce simple trichoblasts near the branch tips (Image E).

We have uncovered three genetic groups in this morphospecies complex and taxonomic work is needed.  This is currently in our database and BOLD as Polysiphonia sp. 3stricta. This species has been collected from mid intertidal pools to subtidal at 30 m (the deepest of the three genetic groups) growing on rock, invertebrates and other algae. We have genetically verified collections from Chuchill, MB, throughout Labrador, NL, Atlantic Canada, through New England to CN.

GWS044252 copy.jpgImage A. Specimen from the low intertidal on rock from Musquash Head Light, NB (GWS044252).

GWS044252-0004Image B. Close up of basal system stolons and displaying rhizoids are not cut off from their bearing cell (GWS044252).

GWS044252-0003.jpgImage C. Apical cells have a dome shape (GWS044252).

GWS044252-0001Image D. Axes are ecorticate and consist of four pericentral cells that can spiral in some segments. Segments can be many times longer than wide (GWS044252).

GWS044252-0008.jpgImage E. Simple trichoblast formed near the branch tip (GWS044252).