Electronic Flora of South Australia Genus Fact Sheet

Genus DESMARESTIA Lamouroux 1813: 43, nom. cons.

Phylum Phaeophyta – Order Desmarestiales – Family Desmarestiaceae

Thallus (sporophyte) 10–100 cm (-5 m) long, terete to compressed or foliose, complanate, usually much branched pinnately, with a more or less conspicuous midrib (and lateral veins in some) in ligulate species, branches linear, often dentate on margins but becoming entire, arising from a discoid holdfast. Growth trichothallic, with an apical, oppositely branched, filament which wears away above, becoming heavily corticated below with the axial filament remaining distinct. Structure of a large-celled medulla, with hyphal cells surrounding the axial filament and between the medullary cells, and a small-celled cortex which increases by largely periclinal divisions. Gametophyte microscopic, filamentous, branched.

Reproduction: Sporophyte with unilocular sporangia developed from scattered cortical cells, or terminating short cortical filaments, or in sori either as raised mounds or extending over the surface and accompanied by paraphyses. Gametophytes monoecious or dioecious, the female with larger cells and the oogonia producing a single egg which is extruded at the cell apex; antheridia single or clustered, each forming one sperm.

Life history diplohaplontic and heteromorphic.

Type species: D. aculeata (Linnaeus) Lamouroux, type cons.

Taxonomic notes: A genus of numerous species, many of which are variable in thallus dimensions (Chapman 1972), with the sporangia known for relatively few species (Moe & Silva 1977b). Anderson (1985) has discussed the southern hemisphere ligulate forms.

Some oppositely branched ligulate species (e.g. D. ligulata) have free sulphuric acid in the cell vacuoles and deteriorate rapidly after collection, affecting also other algae adjacent to them.

References:

ANDERSON, R.J. (1985). Morphological and taxonomic relationships among branched, ligulate members of the genus Desmarestia (Phaeophyceae, Desmarestiales), with particular reference to South African D. firma. Can. J. Bot. 63, 437–447.

CHAPMAN, A.R.O. (1972). Morphological variation and its taxonomic implications in the ligulate members of the genus Desmarestia occurring on the west coast of North America. Syesis 5, 1–20.

LAMOUROUX, J.V.F. (1813). Essai sur les genres de la famille des thalassiophytes non articulées. Ann. Mus. Hist. Nat., Paris 20, 21–47, 115–139, 267–293, Plates 7–13(1–7).

MOE, R.L. & SILVA, P.C. (1977b). Sporangia in the brown algal genus Desmarestia with special reference to Antarctic D. ligulata. Bull. Jap. Soc. Phycol. 25, 159–167.

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
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