Electronic Flora of South Australia Family Fact Sheet

ORDER SPHACELARIALES Oltmanns

Phylum Phaeophyta

Thallus usually heterotrichous, tufted, 1 mm to 30 cm long, usually densely and irregularly or verticillately branched, branches indeterminate or determinate, polystichous (rarely uniseriate), epiphytic or epilithiC, attached by rhizoids or with a prostrate or stoloniferous base. Branches terete with tiers of cells formed by transverse division of the apical and subapical cells, followed by longitudinal divisions (except in Discosporangium and Sphacella) and in some taxa then by secondary transverse divisions, remaining ecorticate or becoming heavily corticate with small cells or by rhizoids. Growth by means of a prominent elongate apical cell to each indeterminate branch, with smaller apical cells in branches which have become determinate. Branches originating either from the apical cell ("acroblastic"), from the upper cell of the subapical transverse division ("hemiblastic") or from a subdivision of this cell ("meriblastic"). Phaeophycean hairs often present, usually formed by acroblastic branching. Phaeoplasts numerous per cell, parietal, lenticular, without pyrenoids. Wall blackening (then fading) usual with Eau de Javelle (aqueous sodium hypochlorite).

Reproduction: The sporophyte with unilocular meiosporangia and the gametophytes monoecious or dioecious, isogamous, anisogamous or oogamous. Direct reproduction by neutral plurilocular sporangia probable in some species, and in others by absence of meiosis in the unilocular sporangia. In subgenus Propagulifera of Sphacelaria by vegetative propagula.

Life history diplohaplontic with essentially isomorphic generations.

Taxonomic notes: An order of three families, well represented on southern Australian coasts, plus the doubtfully placed Choristocarpaceae. This is a distinctive and easily recognised order from the terete branches, conspicuous apical cells, and characteristic segmentation of most genera. The number of genera in the order has varied from 15 to about 8 (Prud'homme van Reine 1982, pp. 2,3).

Prud'homme van Reine (1978) has analysed the European species by numerical methods, and has (1982) given an account of the order and of the family Sphacelariaceae in detail. His results are in general agreement with the classical taxonomic views of Sauvageau (1900–1914). The reproduction of S. rigidula has been analysed in detail by van den Hoek & Flinterman (1968).

Southern Australian taxa are comparatively well known and most are distinctive. It is likely, however, that further species than those given below occur in Sphacelaria, especially small species epiphytic on larger brown algae.

References:

PRUD'HOMME VAN REINE, W.F. (1978). Criteria used in systematic studies in the Sphacelariales. In Irvine, D.E.G. & Price, J.H. (Eds), Modern approaches to the taxonomy of red and brown algae. Systematics Association Special Vol. 10, pp. 301–323. (Academic Press: London.)

PRUD'HOMME VAN REINE, W.F. (1982). A taxonomic revision of the European Sphacelariaceae (Sphacelariales, Phaeophyceae). Leiden Botanical Series, Vol. 6. (Brill: Leiden.)

SAUVAGEAU, C. (1900–1914). Remarques sur les Sphacélariacées. This was published as follows: pp. 1–51, J. de Bot. 14 (1900); pp. 51–167, Ibid. 15 (1901); pp. 167–228, Ibid. 16 (1902); pp. 228–332, Ibid. 17 (1903); pp. 332–348, Ibid. 18 (1904); pp. 348–480? (1904) and pp. 481–634 (1914), separately published with the above reprinted, 1914. (Bordeaux.)

VAN DEN HOEK, C. & FLINTERMAN, A. (1968). The life history of Sphacelaria furcigera Kuetz. (Phaeophyceae). Blumea 16, 193–242.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

KEY TO FAMILIES OF SPHACELARIALES

1. Filaments without subdivision of subapical cells and without longitudinal walls; propagula absent or 1–3 celled, elongate-ovoid; walls not darkening with Eau de Javelle

CHORISTOCARPACEAE

1. Filaments with subdivision of the subapical cell and with (except Sphacella) longitudinal walls in many to all cells; propagula (when present) with 2–4 arms or lobes; walls darkening with Eau de Javelle

2

2. Thallus without cortication over the segments (apart from basal rhizoidal cortication) which in most taxa (except Sphacella) have longitudinal walls; laterals arising by hypacroblastic branching which is irregularly radial or distichous; reproduction with unilocular sporangia and isogametes or anisogametes from plurilocular gametangia or with neutral sporangia; propagula present or absent

SPHACELARIACEAE

2. Thallus heavily corticated shortly or distantly behind the apices with small, isodiametric cells or with rhizoids; laterals arising by acroblastic branching which is irregularly radial, distichous or verticillate; reproduction by unilocular sporangia and isogamous, anisogamous or oogamous gametangia; propagula absent

3

3. Branching mostly acroblastic, irregularly radial to distichous; sexual reproduction anisogamous or oogamous; cortication by rhizoids or pseudoparenchymatous

STYPOCAULACEAE

3. Branching of main axes hypacroblastic, subdichotomous, producing more or less verticillately arranged laterals with acroblastic branching; segments of main axes showing secondary growth in length and width; cortication of axes by several layers of isodiametric cells; sexual reproduction isogamous

CLADOSTEPHACEAE


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