This alga forms orangish to dark red tufts in our flora, individuals ranging from 3-20 cm in height (Image A). Some individuals appear to be almost radially loosely-alternate to irregularly branched (Image B), but a closer look at the tip reveals the regularly alternating nature of the determinate laterals formed on each vegetative segment (Image C). These determinate laterals are uniseriate and subdichotomously branched, largely lending the fluffy appearance to the individuals, and are replaced by indeterminate laterals in a regularly or irregularly alternating fashion along the axes to lend the overall branching pattern to the individuals (Image A). The plants have polysiphonous construction with a central axial filament surrounded by 4-5 periaxial cells (Image C), these covered at some distance from the tips by a rhizoidal cortical covering (Image D).
A recent introduction to our flora (Schneider 2010, Savoie & Saunders 2013); typically subtidal (1-17 m) growing on hard substrata and other algae; at times dominating the algal turf at sites and forming a significant component of the drift algae. There is a slight chance of confusion with Dasya baillouviana (S.G. Gmelin) Montagne, but that species is larger, more sparsely branched, and heavily corticated to the tips masking signs of its polysiphonous construction.
Image A. Dasysiphonia japonica in situ from the subtidal (3 m on other algae) at Birchy Head, NS; GWS039643).
Image B. View of the overall branching habit of the indeterminate, and shorter determinate, branches on this species (drift, Fox Point Beach, NS; GWS039587).
Image C. Close up at the growing tips. Monosiphonous determinate laterals alternating on each vegetative segment with the polysiphonous construction of the main and indeterminate axes visible and not obscured by surface cortication (GWS039587).
Image D. Surface view of the elongate rhizoidal cortication, which obscures the polysiphonous construction (GWS039587).