Individuals of this species can be highly variable in morphology, size and colour (yellowish to brownish red). Fronds are typically 5-15(30) cm tall and form in clumps from a crustose holdfast. Despite their variability, fronds are characterized by dichotomous branching in a single plane (Image A), which isn’t always obvious when the specimen is first observed as the typically bushy habit can mask these details (Image B). In transverse section blades have a tangled mesh-like medulla of thick walled filaments (4-8 µm wide) supporting a relatively thick cortex of 7-10 cell layers (Image C). Tetrasporangial individuals develop oval to irregular shaped dark red sori near branch tips (Image D). Carposporophyte development is internal producing large oval swellings that tend to bulge on one surface bending the fronds and producing a slight indent on the opposite surface (Image E).
Chondrus crispus can easily be confused with some gametophytic specimens of Mastocarpus stellatus (Stackhouse in Withering) Guiry, but individuals of the latter species typically have distinct papillae formed on their blade surfaces and thicker margins resulting in a stronger u-shaped profile to the frond (Image F). In addition, Chondrus crispus can display a bluish iridescence (Image G).
We have genetically verified records of this species from RI to the island of NL, typically mid pools through low intertidal to subtidal (15 m) on rock. We have also uncovered an unattached population growing on mud among seagrasses in a saltwater lagoon in NB (Image H). This species can be highly variable in morphology, some of which is recorded in the BOLD taxonomy browser.
Image A. Pressed specimen showing the dichotomous branching of the flattened fronds (low intertidal pool on rock, Lepreau, NB: GWS003575).
Image B. Thalli are commonly bushy in habit masking the diagnostic features (subtidal (4 m on rock) Gaulman Pt., NS; EGWS000349).
Image C. Unstained transverse section displaying the irregular mesh-like habit of the thick-walled medullary filaments bearing a cortex of 7-10 cell layers (low intertidal at Point Pleasant Park, NS; EGWS000473).
Image D. Tetrasporangial sori developing in the fronds of an individual from the subtidal (3 m) on rock, east of Cape Spencer, NB (GWS042865).
Image E. Carposporophytes developing in the fronds of an individual from the subtidal (3 m) on rock, east of Cape Spencer, NB (GWS042871).
Image F. Side by side comparison of thickening at the margins and the consequent curling of the blade to yield a u-shaped profile in juvenile Mastocarpus stellatus (Stackhouse in Withering) Guiry (right, lacks the diagnostic papillae; EGWS000472) versus C. crispus (left; EGWS000473).
Image G. Specimen with blue iridescence (upper intertidal pool on rock, Letete exposed biodiversity site, Bay of Fundy, NB; EGWS001079).
Image H. Individual tangled among seagrasses from an unattached population in Kouchibouguac Lagoon, NB (subtidal 1.5 m; GWS006233).
Seaweed of Canada 