Green (Image A) to yellowish green (Image B) tubes, ~1-1.5 cm tall and ~1 mm wide at more exposed locations becoming ~5-8 cm tall and up to 2 mm wide at some sheltered locations (Featured Image above). Upper regions of the thalli only slightly contorted although commonly compressed with rare branching from basal regions, the tubes arising from a parenchymatous base (Image C). In surface view cells at the base of the erect tubes are elongate and slightly rhizoidal in appearance, 2-4 µm wide by 16-22(+) µm tall (Image D). Cells lower on the tube are polygonal to rectangular, 3-6 µm wide by 5-14 µm tall, and distributed in weak meandering rows (Image E) or more typically at random (Image F). Mid (Image G) and upper (Image H) vegetative cells are irregular in shape, angular to rounded, 3.5-10(12) µm in dimensions, random in distribution with slight spacing between the cells (i.e. not tightly compact). Low on the tubes sections are 24-26 µm thick, always with a thick inner wall, which can be weakly striated in appearance, the cells 3.5-5 µm wide by 10-12 µm long (Image I). Sections from mid to upper tube are 14-26 µm in thickness (those that are thinner having limited and irregular inner wall thickening), but the cells range from rectangular (Image J) to square (Image K) in different individuals, cells 4-6 µm wide by 6-15 µm long, with variable levels of striation evident (Images J-K). In addition to being tubular and compressed in upper thallus regions, this genetic group is also distromatic in part (Image L). In this species the focal plane could be adjusted on medium width tubes to reveal the thickness of the inner tube wall (Image M). In a few tubes septa traversed the cavity near the base (different species?; Image N). Fresh material reveals a single lobed/stellate chloroplast per cell, each with a prominent central pyrenoid.
We have nine genetically verified records from Atlantic Canada and Churchill, MB. Collections were essentiality green to yellow turfs of obvious short tubes (i.e. they do not look filamentous in the field as is the case with some other species, e.g. Blidingia marginata (J.Agardh) P.J.L.Dangeard ex Bliding) on rock and cobble in the upper intertidal, either bare or submerged in pools.
This identification is tentative. This genetic group joins the type Blidingia minima (Nägeli ex Kützing) Kylin in a complex in our phylogenetic analyses. However, as we have uncovered ten species during our surveys of Canadian waters (including four in this complex), and with only eight total collections from BC (that flora typically richer than the NW Atlantic), there is considerable taxonomic work remaining for this genus in our waters. This genetic group lacks a firm match for tufA in GenBank, although it is close sister to (98.43% similarity) to a specimen assigned to Blidingia minima (Nägeli ex Kützing) Kylin from Germany (KT29028). However, most of the differences in tufA are at ambiguities in the GenBank entry and these are probably a single genetic group extending the range to Europe. Ignoring “Blidingia minima (Nägeli ex Kützing) Kylin sensu lato BoF” and “Blidingia minima (Nägeli ex Kützing) Kylin sensu lato Haida Gwaii“, deciding which genetic group is best assigned to Blidingia chadefaudii versus Blidingia minima (Nägeli ex Kützing) Kylin is difficult (assuming these names are even assignable to these genetic groups). Both genetic groups are present in Europe based on matches in GenBank. This genetic group has been assigned to Blidingia chadefaudii because the specimens have consistently thick inner walls (at least low on the tube although this can be variable within an individual tube) at times with obvious striations (although not exclusive to this species, for example see Blidingia subsalsa (Kjellman) Kornmann & Sahling). In addition, cells in the upper regions of tubes for this genetic group are slightly larger, 4-10(12) µm versus 3-8(9) µm, and less compact (more space between cells) then is true for the genetic group tentatively assigned to Blidingia minima (Nägeli ex Kützing) Kylin. These features are at least consistent with these tentative name assignments (see Burrows 1991). Any thoughts on more appropriate name assignments are welcome.
Image A. Typical green tubes of this species from upper intertidal on rock, Sam Orr’s Pond, NB (GWS037970).
Image B. Pressed specimen lighter green to yellowish in colour from upper intertidal on rock, White Pt., NS (GWS007791).
Image C. Tubular thalli rise from parenchymatous bases, branching rare from near the base (arrow), upper regions slightly contorted and locally compressed (intertidal on rock, Deer Arm, Bonne Bay, NL; GWS007133; rehydrated from press).
Image D. Cells in the basal region are elongate and slightly rhizoidal in appearance (GWS007791; rehydrated from press).
Image E. Vegetative cells near the base of the erect axes can be elongate and distributed in weak meandering rows (upper intertidal on rock, Meteghan (front of ‘Auberge du Capitaire), NS; GWS007920; rehydrated from press).
Image F. Vegetative cells near the base of the erect axes with a random distribution (GWS007791; rehydrated from press).
Image G. Vegetative cells mid thallus (GWS007791; rehydrated from press).
Image H. Vegetative cells upper thallus, which are typically slightly less compact than in the genetic group here assigned to Blidingia minima (Nägeli ex Kützing) Kylin (GWS007791; rehydrated from press).
Image I. Section low on a tube with thick inner walls and weak striation, the cells rectangular in shape (GWS007791; rehydrated from press).
Image J. Section from near the top of the tube with thick inner walls, moderate striation and rectangular cells (GWS007791; rehydrated from press).
Image K. Section from near the top of the tube with thick inner walls, strong striation and square cells (GWS007920; rehydrated from press).
Image L. Section revealing region of distromatic development out to the margin with minimal thickening of the inner wall (GWS037970; rehydrated from press).
Image M. Focal plane adjusted on a whole mount tube to reveal the thick inner wall (GWS007920; rehydrated from press).
Image N. Septa traversing the cavity close to the base in a tube (GWS007920; rehydrated from press).