Bonnemaisonia californica Buffham (BC)

This species forms an occasional element of the subtidal west coast flora. Gametophytic individuals are red in colour when observed in situ, 5-25 cm tall and flattened with a percurrent central axis, typically <2 mm wide, lending the fronds a feathery appearance (Image A). A closer view reveals the regularly-alternating, opposite determinate (spine-like) and indeterminate branches (Image B). This species produces hooks which can be relatively fine and rare (Image A) to more obvious and abundant (Image B) in different individuals. Whole mount reveals the elongate and slightly pointed apical cells from which the uniaxial development takes place (Image C) and gland cells are commonly visible on the thallus surface (Image D). The cystocarps (postfertilization development) terminate modified indeterminate branches and are consequently positioned alternately on the axes (Image E) being broadly ovate with an obvious ostiole (Image F). Spermatangia are on separate individuals (dioecious) and similarly form on modified indeterminate branches (Image G) forming a near continuous surface covering of these axes (Image H). The presumably filamentous tetrasporophyte has not been collected in our waters to date, but we have documented them for the congener Bonnemaisonia hamifera Hariot.

We have 35 records of this delicate species from throughout BC and into neighbouring WA. Individuals were collected from the subtidal (2.5-16 m) most commonly on rock and other hard substrata (e.g. invertebrates), rarely on other algae. This is a fairly unique species in the flora and can easily be identified. To the untrained eye confusion with Cumathamnion decipiens (J.Agardh) M.J.Wynne & G.W.Saunders is possible, but that species lacks the distinctive branching pattern of B. californicaBonnemaisonia geniculata N.L.Gardner overlaps in range with B. californica, but that species has broader axes (typically >2 mm), lacks hook-like structures, and is typically epiphytic. 

Image A. Larger individual (21 cm) displaying the narrow and flattened axes, the main axis percurrent. Only a few fine hooks lower (arrows) were observed (subtidal (16 m) on rock, Rennell Sound, BC; GWS001699)

Image B. Collection displaying the determinate branches (arrows) alternating with their opposite indeterminate branches and the hooks (double arrows) that characterize this species (subtidal (7 m) on rock, Rosario Beach Pt., WA; GWS036748).

Image C. Apical cells are elongate and slightly pointed in this species (subtidal (10 m) on rock, Deer Group, BC; B078GWS).

Image D. Numerous gland cells (arrows) are visible in whole mount (subtidal (10 m) on rock, Bradys Beach, BC; GWS000628).

Image E. Cystocarps (arrows) terminating modified alternating indeterminate branches (subtidal (10 m) on rock, Scotts Bay, BC; GWS004108).

Image F. Cystocarps are broadly oval with an ostiole for spore release (B078GWS).

Image G. Spermatangia are produced on modified alternating indeterminate branches (subtidal (5 m) on rock, Tahsis, BC; GWS010313).

Image H. Close up view of the surface spermatangia with gland cells (arrows) still visible (GWS010313).