Grateloupia turuturu Yamada (A)

Blades in this species are undivided or irregularly divided, the margins undulate and with or without marginal proliferations (Image A). Blades can occur solitary or in clumps from a thin holdfast and are slippery to the touch. Ranging in thickness from 150-600 µm, the medulla is sparsely filamentous, composed of irregular but also distinct periclinal and anticlinal filaments, these thin (2-3 µm; Image B). Toward the cortex the filaments produce angular to stellate cells which bear an outer cortex of 3-5 layers of rounded, pigmented cells (Image C). Tetrasporangia are produced among the cortical filaments and range in size from 16-20 wide by 25-30 tall (Image D).

This species was recently introduced to the NW Atlantic flora, as well as many other locations (e.g., Tasmania; Saunders & Withal 2006). Currently we have genetically verified records in the NW Atlantic only from CT to south of Cape Cod, MA, although records to mid ME have been reported (Mathieson & Dawes 2017). Commonly in lower pools, along the sublittoral fringe, and in the shallow subtidal on rock. This species can be highly variable in morphology, some of which is recorded in the BOLD taxonomy browser.


GWS002637.jpgImage A. Pressed Tasmanian specimen from mid intertidal pools on rock (Bicheno, Tas; GWS002637).

GWS001860-0005 copy.jpgImage B. Transverse section (aniline stained; low quality owing to poor rehydration of dried specimen) displaying the sparsely filamentous medulla and branched cortical filaments (drift collection, Narragansett, RI; GWS001860).

GWS001860-0006 copy.jpgImage C. Closeup of the transition from the filamentous medulla to the cortical filaments – the inner cortical cells become angular and at times stellate (GWS001860).

GWS001860-0007 copy.jpgImage D. Closeup of a cruciately divided tetrasporangium in the outer cortical filaments (GWS001860).