Elachista fucicola (Velley) Areschoug (Ar/A)

This species forms distinct tufts on host brown algae (Image A), notably Ascophyllum nodosum (Linnaeus) Le Jolis and various Fucus spp. (e.g. Fucus vesiculosus Linnaeus), in the mid and low intertidal zones, but also extending into the subtidal with its hosts. Erect filaments are free and unbranched (0.6-1.2 cm long by 45-60 µm wide) growing from a basal intercalary meristem at the point of development from the basal cushion (Image B). The basal cushions consist of a compact mass of branched filaments and also bear multicellular clavate paraphyses and unilocular sporangia (32-38 by 80-95 µm) when reproductive (Image C). Erect filament cells are roughly square to rectangular (1:2 width to length ration) and characterized by multiple discoid plastids lacking pyrenoids (Image D).

We have genetically verified collections from the Canadian Arctic extending through to RI south of Cape Cod. Interestingly, in one case we found this species growing extensively on the obligate epiphyte Vertebrata lanosa (Linnaeus) T.A.Christensen, which was highly unusual (Image E). Finally, populations attributed to E. fucicola in BC belong to a separate genetic group. Taxonomic work is needed.

EGWS000690.JPGImage A. Individuals growing on Ascophyllum nodosum (Linnaeus) Le Jolis (mid intertidal, Letete exposed biodiversity site, NB; EGWS000690).

EGWS000690-0023.jpgImage B. Erect filament developing from an intercalary meristem at the point of contact with the basal cushion (EGWS000690).

EGWS000690-0022Image C. When individuals are reproductive the basal cushion also bears distinctive lightly-pigmented clavate paraphyses and oval dark coloured unilocular sporangia (EGWS000690).

EGWS000690-0025.jpgImage D. Cells tend to be square lower in the erect filaments and contain multiple discoid plastids lacking pyrenoids (EGWS000690).

OLYMPUS DIGITAL CAMERAImage E. Genetically verified collection growing densely on the obligate epiphyte Vertebrata lanosa (Linnaeus) T.A.Christensen from a mid intertidal pool, Wallace Cove, NB (GWS041576).