This species forms green mats of typically thin tubular thalli (Image A). Individual tubes are 1-5 cm tall, very thin some collections, only 70 µm wide, but up to ~1 mm near the tops of other tubes. Erect tubes arise from a pseudoparenchymatous base and are rarely branched (i.e. to form multiple major axes, usually low on the thallus) (Image B), but are moderately (Image C) to heavily (Image D) invested with short proliferous branchlets and or spines (Image E). Higher on the tubes the thallus can become compressed in part and contorted, the branchlets themselves rebranching (Image F), and at times tubes are crowned by numerous proliferous appendages (Image G). At the juncture between the basal cushion and erect tube cells can be little modified (Image H) to elongate and slightly rhizoidal in appearance (Image I), the axes here only 25-60 µm wide. Cells low on the tube in surface view are irregular in shape, polygonal to slightly rounded, 3-8(9) µm in diam., these irregularly distributed in wider tubes (Image J) or in meandering rows in narrower tubes (Image K). Cells mid thallus are similarly irregularly distributed or in meandering rows mid thallus, 3-10 µm in diam., the cells being more (Image L) or less (rehydration artifact?; Image M) compact. Cells upper thallus are also in meandering rows on thin tubes and irregular in distribution on wider tubes, the cells 2-11 µm in diam. (Image N). In section a thickened inner wall was absent for the NB collections, 10-12 µm thick (Image O), while collections from BC had thickened inner walls, being 23-26 µm thick (Image P) (this same geographical pattern observed for Blidingia minima (Nägeli ex Kützing) Kylin). Some specimens of this species hosted the green endophyte Chlorocystis moorei (N.L.Gardner) Darienko & al. (Image Q). Fresh material reveals lobed/stellate chloroplast each with a prominent single pyrenoid.
Our four genetically verified records are all from sheltered locations in the mid to upper intertidal and typically in areas of freshwater outflow. We have two each from Haida Gwaii, BC and the St. Croix Estuary, NB. This species is distinctive from others in our flora for its moderate to dense covering of proliferous branchlets, differing from its sister species “Blidingia subsalsa (Kjellman) Kornmann & Sahling Species2” in appearing more as a dominant tube with proliferations than being a branched tube like the latter. Some individuals of Blidingia marginata (J.Agardh) P.J.L.Dangeard ex Bliding can develop proliferous spine-like branchlets as well, but in that species the inner wall is thin in all individuals checked, the cells are more strongly in rows even into the mid thallus, and the proliferous branches are less developed. Considering the low numbers of specimens on which these distinctions are based, further study is needed. It is likely that trustworthy identification in this genus will require molecular markers for most collections. The tufA for this genetic group matches numerous GenBank records from Germany listed as Blidingia sp.
Image A. Collection from upper intertidal on rock in freshwater outflow, St. Croix River mouth estuary, NB (GWS037953).
Image B. Close up of a branched (arrow) tube arising from a parenchymatous base (upper intertidal on rock in freshwater outflow, St. Croix River mouth estuary, NB; GWS37956; rehydrated from press).
Image C. Tubes moderately invested with proliferous branchlets (uppermost intertidal on pebbles, Park at end of Honna Road, Queen Charlotte City, Haida Gwaii, BC; GWS031307; rehydrated from silica vial).
Image D. Heavier investment of proliferous branchlets (GWS031307; rehydrated from silica vial).
Image E. Heavy investment of spine-like branchlets (GWS037953; rehydrated from press).
Image F. Upper tubes become locally compressed and contorted, proliferous branchlets rebranch (GWS031307; rehydrated from silica vial).
Image G. Heavy investment of proliferations at the top of a tube (mid intertidal on cobble, Head of Ammatiers Channel, Haida Gwaii, BC; GWS035326; rehydrated from silica vial).
Image H. Unmodified cells at the base of a tube (GWS37956; rehydrated from press).
Image I. Elongate to slightly rhizoidal cells at the base of a tube (GWS35326; rehydrated from silica vial).
Image J. Cells lower on the tube irregularly distributed (GWS35326; rehydrated from silica vial).
Image K. Cells lower on the tube distributed in meandering rows (GWS37956; rehydrated from press).
Image L. Cells mid tube distributed in weak meandering rows and compact (GWS37956; rehydrated from press).
Image M. Cells mid tube distributed in meandering rows and separated by thicker walls (GWS31307; rehydrated from silica vial).
Image N. Cells upper thallus on a wider tube (GWS037956; rehydrated from press).
Image O. Optical section of a tube from NB lacking a thick inner wall (GWS037956; rehydrated from press).
Image P. Section of a tube from BC with obvious thickening of the inner wall (GWS35326; rehydrated from silica vial).
Image Q. Section revealing the endophyte Chlorocystis moorei (N.L.Gardner) Darienko & al. (GWS35326; rehydrated from silica vial).
Seaweed of Canada 