Sphaerotrichia divaricata (C.Agardh) Kylin (A)

This species certainly speaks Chordariaceae, but is particularly slippery and gooey. So much so that hand sections proved next to impossible. Individuals are light to dark brown and vary in size with some of our specimens 30 cm tall, the pressed voucher here ~25 cm (Image A). Individuals can be sparsely branched, these produced at ~90 degree angles to the bearing axis (Image A), or more profusely branched (Image B) to many orders (Image C). Consequently it is difficult to describe this species in simple terms. Slippery with many branches coming off at ~90 degrees is the best guide. In squash mount the inflated thin-walled medullary cells rapidly grade through 2-3 layers of isodiametric subcortical cells and ultimately the assimilatory filaments (Image D) composed of 3-4 elongate cells and a terminal inflated globose cell, which can be flattened at the top (Image E). This type of assimilatory filament is distinctive for this species in our flora. In addition, typical phaeophycean hairs with a distinct basal meristem are produced in this species (Image E). Unilocular sporangia are produced among the assimilatory filaments and have a distinct obovate shape (Image F).

We have genetically verified records throughout the warmer waters of the Northumberland Strait, Gulf of St. Lawrence and warmer bays of coastal NS, but the recorded distribution extends into neighbouring New England. A summer annual and commonly collected in the drift, this species grows attached from the mid intertidal to subtidal (8 m) on rocks, shells or other algae. Unattached populations are also common in seagrass beds (Featured image above). Polycerea borealis Vinogradvoa also has significantly inflated terminal cells of its assimilatory filaments, but the filaments are longer, 5-12 cells, and the terminal cells are more typically spherical. Furthermore, this is a (sub)arctic species unlike the more temperate distribution for Sphaerotrichia divaricata (C.Agardh) Kylin.

Image A. Pressed voucher collected from the mid intertidal on rock at Cap des Caissie, North of Shediac, NB (GWS007971).

Image B. More proliferously branched free-floating specimen from the subtidal (Pomquet Harbour, NS; GWS032157).

Image C. Branching can occur to 4-5 orders in some individuals (Grand Barrachois, northern bank, St. Pierre et Miquelon; GWS007633).

Image D. Medullary filament bearing isodiametric subcortical cells with a covering of assimilatory filaments composed of 3-4 elongate cells terminated by a surface covering of large inflated cells (drift, Pointe du Chêne Rd., Northumberland Strait, NB; GWS047446).

Image E. Close up of the assimilatory filaments with their inflated terminal cell; as well as a phaeophycean hairs with its basal meristem (GWS047446).

Image F. Unilocular sporangium nestled among the assimilatory filaments (GWS044437).