Gloiosiphonia capillaris (Hudson) Carmichael (BC/A)

This species has an alternation of heteromorphic generations. The gametophytes are red in colour and rather lubricous, typically 5-20 cm tall, sparsely to densely and irregularly branched to three or more orders (Image A). At low magnification there is a banded appearance to the cortical development in younger thallus regions, which are beset with abundant colourless hairs (Image B). Development is uniaxial and an apical cell is obvious at the branch apices (Image C). In transverse section mid thallus the central axial filament is obvious, supports the branched cortical fascicles (two of reportedly four in focal plane), and is surrounded by secondary rhizoids (Image D). The central axial filament and medullary rhizoids (Image E), as well as the cortical fascicles (Image F) can also be easily viewed in a squash mount. Gametophytes produce 1-2 carposporophytes per node giving a weakly banded appearance to the ultimate branches (Image G) and are typically naked in the cortex consisting of a single gonimolobe (Image H). Tetrasporophytes are crustose (Image I) and have been variously assigned to the genus Cruoriopsis (Mathieson & Dawes 2017). Gametophytes are typically rare (locally common) and appear as spring to summer annuals with all of our genetically verified collections ranging from April to August. In the NW Atlantic we have specimens verified from MA to Newfoundland Island, NL. In the Pacific we have verified records from Bamfield to Haida Gwaii, BC, which resolves uncertainty as to the authenticity of records for this species in that province (see Gabrielson & Lindstrom 2018). Also, our records from Haida Gwaii, and most recently on a dive in the Bay of Fundy (17.7.2018), challenge the view that this is a warm water species (see Mathieson & Dawes 2017). We have only a single putative genetically verified record of the tetrasporophyte generation (Image I). OLYMPUS DIGITAL CAMERAImage A. Specimen from New River Beach in the Bay of Fundy, NB, collected in July 2018 (GWS039124). GWS039124-0005 copy.jpgImage B. Young branch tips showing the banded pattern of the cortical development and rich investment of hairs (GWS039124). GWS039124-0006.jpgImage C. Closeup of the apical cell at a branch tip (GWS039124). GWS013703-0026.jpgImage D. Transverse section (aniline stained) revealing the central axial cell (arrow) bearing two branched cortical fascicles and surrounded by secondary rhizoids (low intertidal pool on rock, Lawn Point, Haida Gwaii, BC; GWS013703).
Image E. Squash mount revealing the central axial filament (arrows) and medullary rhizoids (subtidal (6 m) on rock, Black Point (north), Saint John Harbour monitoring site, NB; GWS48727; formalin fixed, aniline blue).
Image F. Close up of cortical fascicles in squash mount (GWS48727; formalin fixed, aniline blue).
Image G. Carposporophytes forming weak banding pattern in ultimate branches (GWS48727).
Image H. Squash mount revealing two mature gonimolobes (GWS48727). GWS014744.jpgImage I. Tetrasporophyte from subtidal (5 m) cobble at Plymouth, MA (GWS014744).