This species forms brownish red to straw coloured tufts, 1-8 cm in height (Image A). Branching is typically subdichotomous with the primary branches produced every 8-19 segments (Image B). Adventitious branches are produced on most individuals, but tend to remain short and do not mask the primary branching pattern (Images B & C). Cells lower on main (partially prostrate?) axes produce multicellular rhizoids (Images D), although cells mid and upper thallus can also produce rhizoids in some individuals. Near the base of the thallus the rhizoids commonly terminate in multicellular attachment pads (Image E). The tips of the erect axes can be slightly curved, but are more typically strongly inrolled, and viewing them under the microscope reveals the domed apical cells of this uniaxial species (Image F). This species is only partially corticated with a clear alternation of corticated nodes and ecorticate internodes, which is evident almost to the apical cells (Image F). Anterior and posterior development of the cortical cells is roughly symmetrical resulting in even development over the pericentral cells (Image G). Near the tips axes are 40-85 µm wide and the segments 0.5-1.5 diameters long with the internodes 0.4 to 1 X longer than the nodes (Image F). Mid thallus segments are 80-180 µm wide and ~1.4-3.2 diameters long with the internodes 1.5-3 X longer than the nodes (Image H). Lower thallus the segments are 75-260 µm wide 6-8 diameters long with the internodes 3-7 X longer than the nodes (Image I). Gland cells and spines absent; hairs rare to abundant (notably at the tips). In section there are six periaxial cells at each node (Image J), these noticeably larger than the surrounding cortical cells (Image G). Gonimoblasts abaxial, 145-260 µm in dimensions, appearing to have a single gonimolobe and 1-2 involucral filaments (Image K). Spermatangia form in extensive sori across the nodes (Image L). Tetrasporangia 1-4 per node, 39-50 µm wide by 53-70 µm long, are partially exposed to more completed immersed in the cortex, decussate to irregular in division (Images M & N, respectively).
This species has 38 genetically verified records largely confined to sheltered or estuarine sites along the Gulf of Saint Lawrence and coastal Newfoundland, the unusual habitat of Sam Orr’s Pond in the lower Bay of Fundy, NB, and the similarly unique Bras d’Or Lakes in Cape Breton, NS. Most recently a collection sent from NY and field identified as Ceramium deslongchampsii Chauvin ex Duby was a genetic match to this species greatly extending the range. The species occurs from the low intertidal to shallow (~2 m) subtidal typically on eelgrass, but also on various hard substrata and other algae and can be a common component of the drift in some areas and seasons. There are no matching sequences in GenBank for COI-5P, LSU or rbcL and this appears to represent a novel NW Atlantic species. Further complicating matters is the possibility that Ceramothamnion translucidum G.W.Saunders & C.W.Schneider can grow epiphytically with Ceramium facetum requiring care in trying to distinguish the two species. They differ at the tips with Ceramium facetum typically having strongly enrolled tips while in Ceramothamnion translucidum G.W.Saunders & C.W.Schneider they are straight to slightly curved. The latter also has 4-5 pericentral cells that differ only slightly in size from the surrounding cortical cells, and the tetrasporangia are largely exposed. The only other strongly banded species in our flora (regular alternation of corticated nodes and ecorticate internodes), Ceramium deslongchampsii Chauvin ex Duby, differs from both of the previous by the branches being widely separated (up to 40 nodes), the tips typically straight and in having four pericentral cells that are markedly larger than the surrounding cortical cells. While Ceramium facetum shares the relatively large pericentral cells, it has six.
Image A. Drift cystocarpic specimen growing on eelgrass (Beach to east of Parlee Park Beach, NB; GWS045988).
Image B. A view of the subdichotomous branching pattern and occasional short adventitious branches (subtidal (1 m) on seagrass, Hay Island, NB; GWS027624; rehydrated from silica vial).
Image C. Close up of short adventitious branch (Whycocomagh Picnic Area Site #2, Bras d’Or Lake, Cape Breton, NS; GWS006966; rehydrated from press; aniline stained).
Image D. Close up of multicellular rhizoids (subtidal (1 m) on seagrass, Kouchibouguac lagoon seagrass beds, NB; GWS006224; rehydrated from press; aniline stained).
Image E. Rhizoid terminating in a multicellular attachment pad (GWS045988; formaldehyde, aniline stained).
Image F. Inrolled tips with domed apical cells (GWS045988; formaldehyde, aniline stained).
Image G. Anterior and posterior cortical development is roughly symmetrical; note the relatively large underlying periaxial cells (drift on eelgrass, Estuary to east of Parlee Park Beach, NB; GWS045981).
Image H. Axis mid thallus (GWS045981).
Image I. Axes lower thallus (subtidal (1 m) on seagrass, Hay Island, NB; GWS027622; rehydrated from silica vial).
Image J. Section lower thallus reveals six periaxial cells (on rock, upper pond, Sam Orr’s Pond, NB; GWS029906; rehydrated from silica vial; aniline stained).
Image K. Cystocarps (GWS045988; formaldehyde, aniline stained).
Image L. Spermatangia develop in extensive sori across the nodal cortical cells (GWS045988).
Image M. Tetrasporanigum partially emergent from the cortical covering (intertidal on mussel, Alexander Bay Causeway near Terra Nova Park, NL; GWS007433; rehydrated from press).
Image N. Section of tetrasporangium immersed in the cortex (GWS045988; formaldehyde, aniline stained).
Seaweed of Canada 