Pogotrichum sp. 1BoF (A)

Brown tufts, 2-3 cm tall, on coarse algae (Image A). Filaments are uniseriate throughout(?) with unilateral branching and plurangia produced in secund series (Images B and C). Plurangia are sessile on their bearing branch and are intercalary with a few terminal vegetative cells evident (Image D), and strongly oblong, up to 400 µm in length (Image E) and only 12-14 µm wide when mature (Image F). They initiate development mid filament and eventually mature both toward the bearing branch and finally the tip. Although intercalary, it is possible that all but the terminal cell may transition to plurangia leaving the single acute cell at the tip (Image G). Plurangia are commonly observed empty (Image H). Chloroplasts are large discs, 4-7 per cell, with pyrenoids (Image I).

On a routine dive we collected yet another brown clump, more out of boredom than some keen sense of discovery, and returned this beast. Thus our knowledge of its habit and distribution are limited, but it is from the upper-mid Bay of Fundy.

Although we have not yet encountered Pogotrichum filiforme Reinke in our surveys, this unidentified species is a distant sister to that species in preliminary phylogenetic analyses (based on data in GenBank). We have also collected a branched species from the northeast Pacific, which may account for records of Stictyosiphon tortilis (Gobi) Areschoug ex Reinke in that region. It interestingly has a disjunct distribution in the NE Pacific (see Saunders 2014). Further study is needed.

Image A. Collection growing in the subtidal (2 m) on Fredericqia deveauniensis Maggs, L.Le Gall, Mineur, Provan et G.W.Saunders (Duck Pond Beach (rocks west), NB; GWS0044407).

Image B. Uniseriate axes with unilateral branching and secund production of plurangia (GWS0044407; rehydrated from press; aniline blue).

Image C. Close up of uniseriate axes (GWS0044407; rehydrated from press; aniline blue).

Image D. Plurangia secund and sessile on the bearing branch; terminated by 2-6 vegetative cells (arrows) (GWS0044407; rehydrated from press; aniline blue).

Image E. Strongly oblong plurangia (GWS0044407; rehydrated from press; aniline blue).

Image F. Mature region of plurangium (GWS0044407; rehydrated from press; aniline blue).

Image G. Single spine-like terminal cell of plurangial branch (GWS0044407; rehydrated from press; aniline blue).

Image H. Plurangium after releasing zoids (GWS0044407).

Image I. Chloroplasts are relatively large flat discs with pyrenoids (GWS044407).