We have a single specimen for this genetic group, which contributed to a green turf on upper intertidal rocks. None of that would be revealed from the press of this specimen (Image A). Individual filaments can be anchored strictly by a modified basal cell (Image B), but more commonly this is augmented by intramatrical (produced within the “matrix” or cell walls and surrounding cuticle) (Image C) and extramatrical (produced free of the filament matrix) (Image D) rhizoids descending from adjacent cells. Lower vegetative cells range from disc-like to rectangular, 16-30 µm wide by 13-48 µm tall (Image E). Mid to upper thallus vegetative cells are typically squat, 42-49 µm by 16-45 µm, and slightly barrel shaped in appearance (Image F), but can be disc shaped, rectangular and occasionally oval (43-46 µm by 52-57 µm) in habit (Image G). The last mentioned may be akinetes (asexual sporangia that produce a nonmotile spore, see Scagel (1966, p. 77)). Reproductive structures (gametangia?) are slightly longer than wide, 48-55 µm wide by 56-60 µm long, and slightly barrel shaped (Image H).
We have a single specimen assigned to this genetic group, collected from upper intertidal on rock at ‘Lands End’ (up the left side of Pachena Bay where it opens to the ocean), Bamfield, BC. Using Gabrielson & Lindstrom (2018) this might be identified as morhospecies Urospora penicilliformis (Roth) Areschoug for the common squat and barrel shaped cells or Urospora neglecta (Kornmann) Lokhorst & Trask based on the smaller cell sizes. It is distinct in rbcL-3P data from both of these species as identified in these pages from the NW Atlantic (which may be misidentified). Using Scagel (1966) the resulting morphological identification wold be Urospora mirabilis Areschoug, which with a type locality of the North Sea may be correctly synonymized with Urospora penicilliformis (Roth) Areschoug.
It is common for what otherwise looks like a unialgal carpet on rock, or mat of green filaments in an estuary, to be a chaotic mix of green species including, among others, various Blidingia spp., Percursaria percursa (C.Agardh) Rosenvinge, Rosenvingiella polyrhiza (Rosenvinge) P.C.Silva, Urospora spp. and Ulothrix spp. Identification should be done carefully, as should attempting to match DNA sequences to individual species. Owing to the wonders of PCR, a clean sequence could be from any one of the species present in a collection and not necessarily the dominant one on which the microscopical identification was based. Consequently, I am not yet 100% certain that the genetic groups and morphospecies completely align for the various Urospora spp. presented on this site. This is my best guess after consulting the pertinent literature (mostly Scagel (1966), Burrows (1991), Sears (2002), Brodie et al. (2007), Mathieson & Dawes (2017) and Gabrielson & Lindstrom (2018)). Considerable work remains for this genus in our flora.
Image A. Press of our only collection (upper intertidal on rock at ‘Lands End’ (up the left side of Pachena Bay where it opens to the ocean), Bamfield, BC; GWS008147).
Image B. Filament possibly attached only by the rhizoidal basal cell (GWS008147).
Image C. Attachment augmented by intramatrical descending rhizoids (GWS008147).
Image D. Attachment augmented by extramatrical and intramatrical descending rhizoids (GWS008147).
Image E. Vegetative cells near the filament base (GWS008147).
Image F. Cells mid to upper thallus are typically squat and slightly barrel shaped (GWS008147).
Image G. Upper to mid thallus cells can be variable in shape including rectangular and occasionally large ovals (possibly akinetes) (GWS008147).
Image H. Reproductive structures are slightly longer than wide with a weak barrel shape (GWS008147).
Seaweed of Canada 