Eudesme borealis H.Kawai, T.Hanyuda & A.F.Peters (BC/Ar/A)

Thalli 10-50 cm tall, gelatinous and gooey in texture, yellowish to dark brown, sparsely branched to 1-2(3) orders, with terete axes (Image A). Growth is sympodial with a relatively thin central medullary region and dense cortical covering (Image B). Medullary filaments are composed of large cells, 20-58 µm wide by 90-188 µm tall, which have cross connections (Image C). The surrounding cortex has a thick subcortical layer, cells 10-22 µm wide by 17-51 µm tall, subtending the outermost layer of assimilatory filaments, cells 6-9 µm wide by 12-26 µm tall (Image D). Phaeophycean hairs were common, borne low on assimilatory filaments with obvious multicellular basal meristems (Image E). Elongate to nearly spherical unilocular sporangia, 25-45 µm wide by 57-88 µm tall, are borne on lower cells of the assimilatory filaments (Image F).

We have collections from Haida Gwaii, BC, Nome, AK, Churchill, MB, Labrador, Nl, throughout the Canadian Atlantic provinces, down to RI and also in Bergen, Norway. Collected from high intertidal pools to the shallow subtidal (10 m) growing on rock and other hard substrata, to bark, seagrass and other algae.

Image A. Specimen from the subtidal (3 m) on rock at Sledge Island near Nome, AK (GWS042523).

Image B. Squash mount revealing central medulla and surrounding cortex (subtidal (10 m) on rock, White Pt., NS; GWS007813; rehydrated from press, aniline blue stained).

Image C. Close up of medullary filament cells (GWS007813; rehydrated from press, aniline blue stained).

Image D. Medullary (M), subcortical (SC) and assimilatory filament (AF) cells in squash mount (GWS007813; rehydrated from press, aniline blue stained).

Image E. Phaeophycean hair born low on assimilatory filament with a basal multicellular meristem (arrow) (GWS007813; rehydrated from press, aniline blue stained).

Image F. Unilocular sporangium (GWS007813; rehydrated from press, aniline blue stained).