Spongonema tomentosum (Hudson) Kützing (BC/A)

This species manifests as clusters of short, 1-8 cm, individuals on Fucus distichus Linnaeus (Image A), but possibly also on some hard substrata. Filaments are uniseriate with cells typically rectangular, 16-25 µm wide by 25-63 µm long, and containing ribbon-like plastids with multiple pyrenoids (Image B). Rhizoids are abundant and bind the vegetative filaments into the rope-like strands (Image C). Plurilocular structures are typically terminal and on short 1-2 celled stalks (Image D).

We have few genetic records for this species in the Canadian (and contiguous waters) flora, one each from BC, ME and NS, but this is possibly a sampling artifact (easily overlooked or confused with Pylaiella washingtoniensis Jao in the field; we acquired multiple hits on a short collecting trip to Norway, which does not have Pylaiella washingtoniensis Jao). Specimens were almost exclusively from mid to low intertidal, in pools or exposed, on Fucus distichus Linnaeus. Possible confusion with Pylaiella washingtoniensis Jao can occur owing to the rope-like strands and corresponding vegetative rhizoids, however, this species has discoid plastids rather than the ribbons of S. tomentosum.

GWS039898.JPGImage A. Rope-like strands of individuals clustered on mid intertidal (in pool) Fucus distichus Linnaeus at Ormhilleren, Norway (GWS039898).

GWS045103-0016 copy.jpgImage B. Uniseriate strands with cells containing ribbon-like plastids containing multiple pyrenoids (mid intertidal on FD, Letete exposed biodiversity site, Bay of Fundy, NB; GWS045103).

GWS045103-0018 copy.jpgImage C. Rhizoids are abundant in this species (GWS045103).

GWS045103-0017 copy.jpgImage D. Terminal plurilocular structure borne on a single celled stalk (GWS045103).