Membranoptera fabriciana (Lyngbye) M.J.Wynne (Ar/A)

In the Membranoptera morphology this species is distinct with a central midrib and bordering translucent monostromatic wings (Image A), while the Pantoneura morphology (Image B) can be more difficult to field identify (see Wynne & Saunders 2012). The latter can be confused with M. carpophylla (Kützing) Athanasiadis, but this species has a more robust cortex, which masks the central axial filament in contrast to the cortex in the Pantoneura morph of M. fabriciana (Image C). Geography seems a useful tool as well with M. carpophylla thus far confined to the Arctic. In whole mount near the apices of the Membranoptera morphology, the cells of the primary cell row subtending the apical cell are not obscured by cortication for 5-6 cells (Image D) while the pattern of venation is apparent (Image E). In cross section the blades are typically tristromatic at the midrib and monostromatic from the midrib to the margin (Image F). Tetrasporangia form sori near the blade tips that are clearly visible in surface view (Image G). Tetrasporangia are spherical, 32-40 µm in diameter, with tetrahedral division (Image H). Genetically verified records of this species occur at semi-sheltered to exposed sites and from the low intertidal into the subtidal to 25 m. It grows on a wide variety of substrata, being particularly common on other macroalgae. We have genetically verified collections from southern ME to northern Labrador, NL. At times confused with narrow morphologies of the Phycodrys fimbriata (Kuntze) Kylin complex, that species has cortication obscuring primary cell rows only 2-3 cells below the apical cell and venation is not obvious near the apices in whole mount. GWS002324.jpgImage A. Specimen displaying the Membranoptera morphology, subtidal (20 m) on rock from Louisbourg, NS (GWS002324). GWS007303.jpgImage B. Specimen displaying the Pantoneura morphology, subtidal (25 m) on Dilsea from Bonne Bay, NL (GWS007303). GWS032050 (20X)lowImage C. Surface view 1 cm down from tip; central axial cells obvious through cortex (subtidal (17 m) Pantoneura morphology at Birchy Head, NS; GWS032050). GWS042822-0017 copy.jpgImage D. Whole mount (aniline stained) displaying the primary cell row unobscured by cortication for six cells (arrows) subtending the apical cell (A) (subtidal (15 m), Scatarie Bank, off Cape Breton, NS; GWS042822). GWS042822-0018 copy.jpgImage E. Whole mount (aniline stained) displaying clear main and micro-venation near the branch apices (subtidal (15 m), Scatarie Bank, off Cape Breton, NS; GWS042822).
Image F. Blade in cross section with three cell layers at the midrib and a single layer toward the margin (low intertidal pool on algae, Wallace Cove Lighthouse, NB; EGWS001005).
Image G. Tetrasporangia visible in surface view near thallus tips (EGWS001005).
Image H. Tetrahedral tetrasporangium viewed in section (EGWS001005).