Clathromorphum “circumscriptum(1)” (Ar/A)

This species forms dusty pink to dark pink crusts on rock, cobble and various other hard substrata (Image A). The margins can be lighter in color, appear raised in some specimens, and form prominent ridges where crusts meet (Image A). In section this species is clearly monomerous (Image B) with a strong hypothallus of 7-10 layers bearing a perithallus of variable depths that sport an obvious meristematic cell subtending the 3-9 celled epithallus (Image B). Cell fusions are abundant in the perithallus and, rarely, buried conceptacles are found (Image C).

We have relatively few genetically verified collections for this genetic group, these from the Bay of Fundy (where we find other more typically northern species, e.g., Hedophyllum nigripes (Rosenvige) Starko, S.C.Lindstrom & Martone), Newfoundland, Quebec and Nunavut. This is thus a cold water species collected in mid tide pools to 5 m in the subtidal on rocks and other hard substratum (e.g., periwinkles) including itself and other species of coralline crusts.

Confusion remains for this genetic group and taxonomic work remains. This genetic group may represent a new species, but is divergent from Clathromorphum circumscriptum (Strömfelt) Foslie (Ar/A) sensu stricto based on type sequence in GenBank for this species. These genetic groups differ in COI-5P, psbA and rbcL.

Image A. Collection on cobble from the mid intertidal (Les Escoumins, QC; GWS008060).

ImageJ=1.52a unit=u00B5mImage B. Vegetative section showing monomerous habit with distinct hypothallus, perithallus, meristem and multi-celled epithallus (Lepreau, NB; GWS039528).

ImageJ=1.52a unit=u00B5mImage C. Buried conceptacle (GWS039528).