Dasya baillouviana (S.G. Gmelin) Montagne (A)


Dasya baillouvia is a relatively distinctive species in its range. Plants can reach 50 cm in length, are pinkish to dark red with the branched axes being 2-4 mm in width but typically coated with abundant pigmented filaments to give the individuals a fuzzy appearance (Image A). These deciduous filaments are uniseriate, sparingly branched and can be 2-5 mm long (Image B). The axes have a central axial filament surrounded by five periaxial cells, this polysiophonous construction covered by further cortical layers of rhizoidal development, the cells of which are rectangular and in long rows in surface view (Image C). The tetrahedral tetrasporangia are formed in tiers in specialized terete branches termed stichidia (Image D) and have a tetrahedral divisions pattern (Image E).

Common in the drift, this species grows attached to rock or coarse algae from mid intertidal pools into the shallow subtidal (10 m). Typically considered a summer annual, based on our genetically verified records this species is restricted to warm water in and around the Northumberland Strait (introduction?). Collections from southern New England are a separate genetic species and clearly more study is needed on the respective distributions of these two entities. There is a slight chance of confusion with Dasysiphonia japonica (Yendo) H.-S.Kim, but that species is smaller, more regularly branched and uncorticated near the tips such that uniseriate and polysiphonous regions are visible.

Image A. Typical habit of this species in the Maritime provinces (Drift, Beach to east of Parlee Park Beach, NB; GWS044430).

Image B. A view of the sparingly branched uniseriate filaments, as well as tetrasporangial stichidia (GWS044430).

Image C. Surface view of the corticated main axes (GWS044430).

Image D. Tetrasporangial stichidium (drift, Pointe du Chêne Rd., Northumberland Strait, NB; EGWS001130).

Image E. Close up of the tetrasporangial stichidia with tetrahedral tetrasporangia (EGWS001130).