Ahnfeltia borealis D.Milstein & G.W.Saunders (BC/Ar/A)

Gametophytes of this cold water species form wiry tufts of dark black to red terete axes, 6-12 cm in height, which can bleach to yellow and white towards the tips (Image A), while the sporophytes are small dark red crusts commonly occurring on cobble (Image B). Gametophytes display irregular to loosely dichotomous branching, not complanate (i.e. not branching in a single plane) (Image A). In transverse section the cells of the longitudinal medullary filaments are 5-12.5 µm in diameter and bear the anticlinal filaments of the thick multi-layered cortex (Image C).

Genetically verified records extend from low intertidal pools in Churchill, MB, to subtidal (2-20 m) throughout the northern range of our waters (see notes below). This species grows on rock or cobble and is partial to sandy habitats.

Distinguishing the gametophyte stage of A. borealis from its congener Ahnfeltia plicata (Hudson) Fries can be challenging. They do typically differ in range with Ahnfeltia plicata (Hudson) Fries being common from RI to the Island of NL, in the NW Atlantic, but we also have a few collections from Churchill, MB, in Hudson Bay where A. borealis is common. On the other hand, A. borealis is predominantly (sub)Arctic in distribution with collections from Nome, AK, to northern Labrador, NL, but with a single drift record for the gametophyte stage on the north shore of PE. More surprisingly one-off collections of the crustose sporophyte were made from Haida Gwaii, BC, and the north shore of Cape Cod, MA. Definitive identification, especially in colder areas of the NW Atlantic flora and in Hudson Bay, requires molecular analyses. This species can be highly variable in morphology, some of which is recorded in the BOLD taxonomy browser.

GWS042310.JPG

Image A. Drift gametophyte stage from Nome, AK (GWS042310).

GWS040299.JPGImage B. Sporophyte stage subtidal (8 m) on cobble (Hogg Island, Torngat, Labrador, NL; GWS040299).

GWS039368-0052.jpgImage C. Transverse section mid thallus displaying the longitudinal medullary filaments bearing the thick multi-layered cortex of anticlinal filaments (subtidal (3 m) Torngats, Labrador, NL; GWS039368).