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PHYCOLOGICAL SOCIETY OF AMERICA
Fauchea: taxonomy
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This section is intended to help you learn to discriminate between species you might find on a beach or in the water (or read about). Most descriptions aided in part by those found in Smith and Abbot & Hollenberg's books.
The red algae are a magnificent Phylum of seaweeds characterized visually by their typically red color. This color is achieved through the utilization of phycoerythrin pigment as a primary pigment. Good reds like Fauchea utilize Floridean Starch to store carbohydrates. This starch is unique in that it exists in the cytoplasm rather than in the chloroplasts where many algae store their carbohydrates. As a phylum, the reds are predominantly marine and live within the subtidal to the intertidal. Of course, like most of the algae, the reds are still photosynthetic, and as such contain chlorophyll pigments to turn sunlight into energy.
The
Floridophyceae are the largest class within Rhodophyta. In that regard,
they are the most diverse, and possess more complex construction.
These algae bear their carpogonia on specialized branches and carpospores
form on gonimoblast filaments.
Probably the most characteristic trait of the Floridophyceae
, one that is often attributed to the entire Phylum, but is in fact absent in
most of the Bangiophyceae, is the unique tripartite life history. No other algae,
or for that matter, organism, experiences such a bizarre life history. Encompassing
haploid and diploid morphs, male and female gametophytes, tetrasporophytes, and
carposporophytes, the life history of these algae is almost surreal. The last
straw, some might say, is that the spermatia of the male gametophyte lack flagella
and are incapable of directing themselves towards the sessile female gametes.
Thus, the females have developed a complex carpogonial branch to catch the spermatia,
who are themselves at the mercy of the currents. See the life
history page for more. .
Antithamnion defectum, a Floridophycean alga
Rhodymeniales are a nice example of the Floridophyceae. Unlike some Floridophyceans, though, their auxiliary cell develops before fertilization from the basal cell of the carpogonial branch and the carposporophyte develops from this cell. Thalli are multiaxial while the branches can be solid or hollow. The Rhodymeniaceae are one of two families, the other being the Champiaceae. The Champiaceae vary from the Rhodymeniaceae in that they have tetrahedrally divided sporangia, colorless spermatangia. The branches are also "cylindrical to narrowly foliose."
Unlike the Champiaceae, the Rhodymeniaceae have cylindrical to foliose thalli, cruciate tetraspores, and their auxiliary cell doesn't fuse after fertilization. The medulla is continuous or becomes hollow by gelatinization of medulla cells. Cortex has 3 or 4 cell layers; secretory gland cells are isolated or clustered and the carpogonial filament is three celled.
The Fauchea algae are characterized by cylindrical to foliose branched thalli often with some iridescence. However, the presence or lack of iridescence shouldn't be a defining factor. The tetrasporophytes used in this study lacked the iridescent beauty of the other samples found. Blades have flabellate division with some fringing in certain species. Their medulla will have between 2 and 4 layers filled with large cells while the cortex has small cells. Cruciate division in the tetrasporangia which are arranged in nemathecoid sori that look like irregular streaks on the tetrasporophyte. Carposporophytes can be either on the margins or scattered across the surface of the thalli.
Fauchea laciniata is a great example of all these taxonomic groups. It is characterized by thalli between 3 and 12 cm (see evolution page for why this is so) that are erect, dichotomo--flabellately branched and deep red in color with, of course, the blue iridescent cast. The cystocarps in this species are scattered across the thalli and are usually markedly coronate. Tetrasporangia cruciate and stored in irregular, elongate, nemathecia. F. laciniata can be found on rocks in the intertidal and subtidal between British Columbia and Northern Baja California, Mexico.
