the immortal red crust

  FHL Marine Botany  ::::::::::::::::::::::::::::::   Taxonomy | Habitat | Morphology | Life History | Ecology | Overgrowth







PHYLUM: Rhodophyta

CLASS: Florideophyceae

ORDER: Hildenbrandiales

FAMILY: Hildenbrandiaceae

GENUS: Hildenbrandia


This genus includes 14 marine species and 5 freshwater species (2). There are at least two marine species found in the Pacific Northwest. Most abundant and easiest to find is H. rubra (Sommerfelt) Meneghini, which is now considered synonymous with H. prototypus Nardo (the first species of Hildenbrandia to be described, back in 1834). The other common species is H. occidentalis Setchell. It is difficult to distinguish between these two species in the field, but H. rubra has irregularly divided tetrasporangia, while H. occidnetalis has zonately divided tetrasporangia (3). H. rubra tends to be thinner and more red, while H. occidentalis tends to be thicker and darker (and can be confused with the 'Petrocelis' phase of Mastocarpus papillatus).

Sherwood & Sheath (2003) report that H. rubra is not monophyletic. The crustose morphology of Hildenbrandia is so simple that variation is hard to document. As such, this taxonomic confusion does not come as a complete surprise. Perhaps the reported distribution of H. rubra is so wide (see Habitat) because the name includes a handful of different species.

There is a rumor that the diverse group of fungi, Phylum Ascomycota, traces its origins to florideophyceaen algae (5). Indeed, roughly half of all ascomycetes (approx. 125,00 species) are lichenized (i.e., associated with an alga) (6). This evolutionary rumor stems from early microscopic investigations of the conceptacles of Hildenbrandia spp., where ambiguous structures were identified as fungal filaments (see Life History for more details about this confusion) (7).






  1. Basic taxonomy retrieved from AlgaeBase. 2009.
  2. Sherwood, A. R. & Sheath, R.G. 2000. Systematic evaluation of the genus Hildenbrandia (Rhodophyta): A synthesis of techniques. Journal of Phycology 36:3(suppl.), pp. 62 - 63.
  3. Dethier, M. N. 1987. The distribution and reproductive phenology of intertidal fleshy crustose algae in Washington. Canadian Journal of Botany 65:9, pp. 1838 - 1850.
  4. Sherwood, A.R. & Sheath, R.G. 2003. Systematics of the Hildenbrandiales (Rhodophyta): Gene sequence and morphometric analyses of global collections. Journal of Phycology 39:2, pp. 409 - 422.
  5. Riedl, H. 1978. The relationship of red algae of the genus Hildenbrandia to aquatic Verrucaria mucosa. Annalen des Naturhistorischen Museums in Vien 82, pp. 363 - 372.
  6. Ammirati, Joseph. January 2009. Lecture at UW.
  7. Pueschel, C.M. 1988. Ultrastructural observations of tetrasporangia and conceptacles in Hildenbrandia (Rhoodophyta, Hildenbrandiales). European Journal of Phycology 17:3, pp. 333 - 341.