Blidingia marginata (J.Agardh) P.J.L.Dangeard ex Bliding Species2 (BC/A)

Species forming green turfs of thin thalli, appearing filamentous (Image A), but this species is tubular at the base, becoming compressed and blade-like (possibly distromatic in part) over the majority of the thallus (Image B). Tubes typically < 0.5 cm tall and <350 µm wide with many arising from a common basal parenchymatous cushion (Image C). Branching rare with numerous bumps and spines apparent at low magnification (Image B). However, many of these are in fact various epi/endophytes (Image D), which can exaggerate the true number of spines/proliferations present (Image E). These proliferations can at times be locally abundant and branched (Image F). Cells at the tube base are elongate and slightly rhizoidal in appearance (Image G). In the erect axes, cells low on the tube are in weak rows, irregular to elongate in shape, 6-11 µm wide by 7-18 µm tall (Image H). Cells mid thallus, 3-7 µm diam., and high on the tubes, 4-10 µm diam., are more irregular in their shape and distribution (Images I & J, respectively). In section our NB collection (ENT10) was only 12-14 µm wide with only slightly thickened inner walls (Image K), which were notably variable in thickness in optical section (Image L). Our collection from South Australia (GWS017339) had thick and variable inner walls, 24-32 µm, with obvious striations (Image M).

At the macro level more filamentous than tubular in appearance, the two genetically verified records for this species were found in the upper intertidal on Fucus (ENT10) and rock (GWS017339). At first our two collections being from NB, Canada and South Australia provided cause to question our results, but there are matching sequences in GenBank for specimens from Germany, Korea, UK, and Venice Lagoon, Italy. This distribution suggests that this species has been widely introduced through anthropogenic activities. This species shares some morphological characteristics (narrow branched tubes with spines/proliferations) with Blidingia marginata (J.Agardh) P.J.L.Dangeard ex Bliding, but the main reason for temporarily assigning it ‘species 2’ is their sister relationship in our preliminary phylogenetic analyses.

Image A. Specimens are fine and appear filamentous (upper intertidal on Fucus, Wallace Cove Lighthouse, NB; ENT10).

Image B. Low magnification reveals the branched flattened tubes (ENT10; rehydrated from press).

Image C. Multiple tubes arising from a parenchymatous cushion (ENT10; rehydrated from press).

Image D. Close up of false spines/proliferations, which are in fact various epi/endophytes (ENT10; rehydrated from press).

Image E. Close up of a real spine-like proliferation (ENT10; rehydrated from press).

Image F. Spines/proliferations can be locally abundant and branched (ENT10; rehydrated from press).

Image G. Cells at the base of the tube are elongate and slightly rhizoidal in appearance (ENT10; rehydrated from press).

Image H. Cells near the base of the tube (ENT10; rehydrated from press).

Image I. Cells mid tube ( note the endophyte Halochlorococcum moorei (N.L.Gardner) Kornmann & Sahling; ENT10; rehydrated from press).

Image J. Cells near the top of the tube (ENT10; rehydrated from press).

Image K. Section with slight thickening of inner wall (ENT10; rehydrated from press).

Image L. Optical section reveals variable thickness of the inner wall (ENT10; rehydrated from press).

Image M. Section with thick striated walls for a collection from Victor Harbour, South Australia (GWS017339; rehydrated from silica vial).