Electronic Flora of South Australia Species Fact Sheet
Phylum Phaeophyta – Order Desmarestiales – Family Arthrocladiaceae
Selected citations: Fritsch 1945: 180, figs 60D, 61E, 62B.D,F,I,M. Harvey 1846, pl. 64. Sauvageau 1931: 95, figs 17, 18. Skinner & Womersley 1983: 65, figs 1C, 3. Taylor 1957: 152, pls 13 fig. 2, 17 figs 7, 8.
Thallus (sporophyte) (Fig. 94C) medium brown, 15–20 cm long, filiform, slender, with long simple branches; holdfast unknown in Australian plants, small and discoid in N. Atlantic specimens. Growth (Fig. 96G) trichothallic at base of a single filament terminating each branch, 40–50 Atm in diameter, lower cells L/B 0.3–0.6, upper cells L/B 1–2, bearing whorls of 4 fascicles of short, usually branched, lateral filaments; below the meristematic zone the axial filament becomes corticated by rhizoids developing from the basal cells of the short laterals and the axial cells. Fronds terete, largely oppositely branched, 0.5–1 mm thick below, tapering slightly to 100–200 µm thick near the apices, bearing more or less whorled, determinate, fascicles 0.4–2 (–3) mm long, giving the branches a fuzzy appearance (Fig. 96F). Structure of thallus with a central, large-celled, axial filament, corticated by the rhizoidal filaments (Fig. 96G) which divide periclinally to form a large-celled medulla and small-celled outer cortical layer, with the cortical cells elongate, 6–12 µ across and L/B 2.5–4 in surface view, with numerous phaeoplasts in the cortical cells and in the whorled fascicles of filaments; fascicles with one main filament oppositely branched and other slenderer filaments. Phaeophycean hairs absent.
Reproduction: Unilocular sporangia formed in moniliform chains (Fig. 96H) on the fascicles of branched filaments, usually 8–24 sporangia and 80–200 µm long, sporangia 10–12 µm in diameter and L/B 0.5–1, producing 10–20 zoospores escaping through a lateral pore. Gametophytes filamentous, branched, reproduction uncertain (Sauvageau 1931, p. 104, figs 19–22).
Type from Cornwall, England (Hudson); in BM or lost?
Distribution: Temperate N. Atlantic; Mediterranean.
Taxonomic notes: In southern Australia, only known from Port Stanvac, S. Aust., 4–5 m deep but not attached (Clarke, 28.xii.1981; ADU, A52837).
A. villosa has not been found since the above collection, when a number of plants were present. They had probably arrived on ships to the Port Stanvac Oil Refinery, but may not have become established in the area.
FRITSCH, F.E. (1945). The structure and reproduction of the Algae. Vol. II. (Univ. Press: Cambridge.)
HARVEY, W.H. (1846). Phycologia Britannica. Plates 1–72. (Reeve: London.)
SAUVAGEAU, C. (1931). Sur quelques Algues phéosporées de la rade de Villefranche (Alpes-Maritimes). Bull. Stn biol. Arcachon 28, 7–168.
SKINNER, S. & WOMERSLEY, H.B.S. (1983). New records (possibly introductions) of Striaria, Stictyosiphon and Arthrocladia (Phaeophyta) for southern Australia. Trans. R. Soc. S. Aust. 107, 59–68.
TAYLOR, W.R. (1957). Marine algae of the Northeastern coast of North America. Rev. Edn. (Univ. Mich. Press: Ann Arbor.)
The Marine Benthic Flora of Southern Australia Part II complete list of references.
Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
Illustrations in Womersley Part II, 1997: FIGS 94C, 96 F–H.
Figure 94 enlarge
Fig. 94. A. Cutleria multifida (ADU, A57020). B. Desmarestia ligulata (ADU, A22255). C. Arthrocladia villosa (ADU, A52837).
Figure 96 enlarge
Fig. 96. A–E. Desmarestia ligulata (A,C–E, ADU, A22255; B, Harvey, Alg. Aust. Exsicc. 47, ADU, A18370). A. Upper branch with laterals, midrib and opposite lateral veins. B. Apex of branch with trichothallic filament and opposite branches, with cortication below the meristematic zone. C. Surface view of cortical cells (some with phaeoplasts) and unilocular sporangia. D. Transverse section of cortex with unilocular sporangia. E. Transverse section of older thallus with central axial filament (on right) and the wing region (on left). F–H. Arthrocladia villosa (ADU, A52837). F. Older branch with more or less whorled (up to four) fascicles of filaments. G. Apex of branch with trichothallic filament bearing 2-4 opposite or whorled laterals, with corticating filaments below the meristematic zone. H. Lateral filaments with chains of unilocular sporangia.
State Herbarium of South Australia