Electronic Flora of South Australia Genus Fact Sheet

Genus COTTONIELLA Børgesen 1919: 333.

Phylum Rhodophyta – Family Sarcomeniaceae

Thallus erect, slender, much branched, branches compressed, with slender monosiphonous filaments; attached by rhizoids from basal parts. Structure. Apical cell dome shaped, axial cells producing 4 pericentral cells, the abaxial first, followed by 2 lateral cells and last the adaxial pericentral cell; the lateral cells each cut off 2 flanking cells, from some or all segments, resulting in compressed branches. Monosiphonous unbranched filaments endogenous from the axial cells, 1 or 2 from each or some of the axial cells. Older branches lightly corticate by rhizoids from the pericentral cells. Lateral branches arising endogenously, the basal, segments usually without flanking cells. Cell uninucleate.

Reproduction: Gametophytes unknown apart from C. triseriata Hollenberg (1967b: 1199, fig. 9).

Tetrasporangial stichidia lateral on lesser branches which may continue growth, with 2 rows of tetrasporangia cut off the lateral pericentral cells which bear a cover cell on each side, and the flanking cells each divide and curve slightly around the stichidium edge.

Type species: C. arcuata Børgesen 1919: 334, figs 334–336.

Taxonomic notes: A genus of probably 4 species (Hollenberg 1967b, p. 1201).

Cottoniella is a distinctive genus, including (as well as the type species) C. filamentosa (Howe) Børgesen (1920, p. 477) and C. fusiformis Børgesen (1930, p. 144, figs 58, 59), both of which have flanking cells on each segment. The latter is often regarded (e.g. Cormaci et al. 1978, p. 256; Cormaci & Furnari 1987, p. 756) as a variety of C. filamentosa, together with var. algeriensis (Schotter) Cormaci & Furnari (1987, p. 756). C. filamentosa has monosiphonous filaments singly from each axial cell, whereas C. fusiformis has usually, but not always, two from each axial cell. Variation in position of filaments is considerable in C. fusiformis, and otherwise they are identical.

The type species, C. arcuata, has only occasional flanking cells and single monosiphonous filaments per segment, flexed to alternate sides on successive segments.

References:

BØRGESEN, F. (1919). The marine algae of the Danish West Indies. Part 3. Rhodophyceae. Dansk Bot. Ark. 3, 305–368.

BØRGESEN, F. (1920). The marine algae of the Danish West Indies. Part 3. Rhodophyceae. Dansk Bot. Ark. 3, 369–504.

BØRGESEN, F. (1930). Marine algae from the Canary Islands. III. Rhodophyceae. Part III. Ceramiales. K. Dan. Vidensk. Selskab. Biol. Medd. 9, 1–159.

CORMACI, M. & FURNARI, G. (1987). Nomenclatural notes on some Mediterranean algae. Taxon 36, 755–758.

CORMACI, M., FURNARI, G. & SCAMMACCA, B. (1978). On the tetrasporic phase of Cottoniella Boergesen (Ceramiales, Rhodomelaceae, Sarcomenioideae). Phycologia 17, 251–256.

HOLLENBERG, G.J. (1967b). New marine algae from the central tropical Pacific Ocean. Amer. J. Bot. 54, 1198–1203.

The Marine Benthic Flora of Southern Australia Part IIID complete list of references.

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

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