Blades are yellowish to dark red and typically present as small ovals (~3-10 cm in height; Image A) to elongate blades some 10-20+ cm wide, but highly variable in length (20 cm to 2 m; Image B). However, thallus shape can also be irregular in some individuals. In cross sections the blades are two cell layers thick, 38-85 µm wide (Image C). Cells have a single stellate plastid containing a central pyrenoid, best viewed in whole mount, which also displays the angular surface cell outline, these 15-32 µm in dimensions (Image D). Margins turn pale as individuals become reproductive (Image E) owing to the development of intermixed zygotosporangial (postfertilization female) and spermatangial (male) packets (Images F & G). As for the genus, the sporophyte phase consists of microscopic filaments growing in calcareous substrata (Image H).
We have genetically verified records from throughout British Columbia, northern Labrador, NL, and throughout the Atlantic provinces (extending into ME), Gulf of Saint Lawrence coasts of QC, as well as Kamchatka and Norway. This species is a spring to summer annual common in low intertidal pools to subtidal (10 m) growing on rock, various invertebrates and other algae. This species is easily distinguished from its congener Wildemania miniata (C.Agardh) Foslie, which has the blade sectored into separate male and female regions. An additional species, Wildemania tenuissima (Strömfelt) De Toni, is recognized in the NW Atlantic by Mathieson & Dawes (2017), but to date there are no genetically distinct records assignable to this species in our flora.
Image A. Young individuals from a low intertidal pool on Dumntia contorta (Gmelin) Ruprecht, from Halls Harbour, NS (GWS011873).
Image B. Large blade growing attached to rock in a low intertidal channel in the Burnaby Narrows, Gwaii Haanas, BC (GWS013435).
Image C. Cross section of vegetative portion of the blade (low intertidal pool on rock, Wallace Cove Lighthouse, NB; GWS031526).
Image D. Surface view of vegetative cells and their stellate plastids (subtidal (10 m) on rock, Deep Cove Point, Bay of Fundy, NB; GWS044340).
Image E. Gametophyte with pale margins (top blade) owing to the development of reproductive structures (low intertidal on Dumntia contorta (Gmelin) Ruprecht, seagrass flats near Lepreau, NB; GWS032365).
Image F. Surface view of reproductive margin with intermixed dark red zygotosporangial packets and smaller pale spermatangial packets (low intertidal on Mastocarpus stellatus (Stackhouse) Guiry, Letete exposed biodiversity site, Bay of Fundy, NB; GWS047208).
Image G. Close up of intermixed dark red zygotosporangial packets and smaller pale spermatangial packets (GWS047208).
Image H. Sporophyte of this species detected through routine DNA barcode surveys growing in a shell (low intertidal (drift?), seagrass flats near Lepreau, NB; GWS039526).