Blidingia dawsonii (Hollenberg & I.A.Abbott) S.C.Lindstrom, L.A.Hanic & L.Golden Species2 (BC)

This species forms turfs of short green tubes (Featured image above), typically < 1 cm tall being thread-like and terete at the base, widening to 0.3-1 mm and compressed near the top (Image A). Many erect tubes arise from the parenchymatous base. Branching is rare and occurs typically low on the thallus (Image C). Cells at the base of erect filaments and into the basal cushion can be elongate and rhizoid like in habit (Image D). Surface view low on the tube reveals cells, 3-12 µm in diam., that are squat to rectangular in shape, angular, and typically in rows (Image E). Mid thallus cells are typically squat to polygonal or rectangular, angular for the most part, and 3-9 µm in diam. (Image F). Near the top of tubes cells, only 2.5-7 µm in diam., are polygonal to irregular in shape, relatively compact and not in rows (Image G). Sectioning reveals a thin inner wall, the overall width only 15-18 µm, with individual cells palisade 4-5 µm wide by 9-11 µm long (Image H). 

All three genetically verified collections, one from BC and two from a single location in CA, were high intertidal on rock at exposed locations. Low on the thallus this species is more reminiscent of Blidingia marginata (J.Agardh) P.J.L.Dangeard ex Bliding owing to the cells being in rows and the rare branching. Higher on the tube the small, irregularly distributed cells are more reminiscent of species in the Blidingia minima (Nägeli ex Kützing) Kylin complex of species. However, in our preliminary phylogenetic analyses, this species is sister to Blidingia dawsonii (Hollenberg & I.A.Abbott) S.C.Lindstrom, L.A.Hanic & L.Golden, with which it shares no notable morphological affinities. There are no close matches in GenBank for the tufA sequence for this group.

Image A. Collection from upper intertidal on rock, Pigeon Point Lighthouse, CA (GWS021396).

Image B. Closer look at the parenchymatous base bearing a number of widening tubes (upper intertidal on rock, Botany Beach, BC; GWS004461).

Image C. Rare branch low on the thallus (GWS004461).

Image D. Cells near tube base and into the cushion can be rhizoid like (arrows) (GWS004461).

Image E. Cells low on a tube (GWS004461).

Image F. Cells mid tube (GWS004461).

Image G. Cells near the top of a tube (GWS004461).

Image H. Section reveals palisade cells and a thin inner wall (GWS004461).