This species forms characteristic reddish-brown wiry tufts (Image A). With its distinctive habit of 20-24 pericentral cells (Image B) and habitat [almost exclusively on Ascophyllum nodosum (Linnaeus) Le Jolis] this is one of the easier species to identify in our flora. Nonetheless, drift plants have been confused with Ceramium spp. as the tips of V. lanosa can have the pincer-like appearance (Image C) characteristic of some species of that genus. However, even at the tips careful observation will reveal multiple pericentral cells (Image C) rather than the banded appearance of the round to cuboidal cortical cells in Ceramium spp.
We have genetically verified records from NL (island) to northern MA, although this species is reportedly more widely distributed in the NW Atlantic. Most of our records are intertidal on Ascophyllum nodosum (Linnaeus) Le Jolis, however, our MA records are subtidal (8 m) reportedly on rock (GWS014765 — I cannot verify this anomalous ‘host’; possibly a drift plant) and Desmarestia aculeata (Linnaeus) J.V.Lamouroux (GWS014795; we have the host vouchered in the case).
Image A. Typically reddish-brown wiry tufts mid intertidal on host Ascophyllum nodosum (Linnaeus) Le Jolis (Tiner Pt., Bay of Fundy, NB; GWS044246).
Image B. Whole mount mid-thallus clearly reveals 9-11 pericentral cells (surface view typically revealing slightly less than half of the total number) (GWS044246).
Image C. Whole mount near the tips reveals pincer-like habit, but the characteristic pericentral cells are still evident (GWS044246).