Electronic Flora of South Australia Species Fact Sheet

Dictyopteris nigricans Womersley 1949: 115, fig. I, pl. 22 fig. 2; 1967: 218.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae

Thallus (Fig. 78C) dark brown, usually densely clumped and 5–20 (–25) cm long, with few to many complanate fronds arising from a matted rhizoidal holdfast 0.5–5.0 cm across and 0.5–2.5 cm long; epilithic. Growth from a row of 8–14 apical cells in a rounded or slightly depressed apex, margin entire. Fronds irregularly alternately branched at intervals of (1–) 2–6 (–10) cm, without proliferous branchlets except following damage, branches linear, usually narrowed below and sometimes near the apices, usually 3–6 (–8) mm broad, with a central midrib, without lateral veins, usually denuded below. Structure (Fig. 79K,L) of wing 5–7 cells thick throughout, occasionally four in fertile regions, midrib 12–20 cells thick; cortical cells (10–) 20–30 (–40) µ across in surface view, L/B 1–2. Hair tufts (Fig. 79K) compact, in an irregular line on each side of the midrib in narrow plants, more scattered on broader blades, hairs arising in clusters from subdivided cortical cells, 16–24 Atm in diameter.

Reproduction: Sporangia (Fig. 79L) scattered between midrib and margin, derived from cortical cells and remaining sunken or very slightly protruding from the surface, with or without a single stalk cell; sporangia subspherical to ovoid or often angular, 60–100 µm in diameter, irregularly tetrahedrally divided. Sexual reproduction unknown.

Type from Pennington Bay, Kangaroo I., S. Aust.; holotype in ADU, A2296.

Selected specimens: Fishery Bay (S.W. of Port Lincoln), S. Aust., uppermost sublittoral (Womersley, 8.i.1987; ADU, 57330-"Marine Algae of southern Australia" No. 283). Sleaford Bay, S. Aust., in reef pools ( Womersley, 6.i.1951; ADU, A13812). West Bay, Kangaroo I., S. Aust., drift ( Womersley, 6.i.1946; ADU, A3485). Pennington Bay, Kangaroo I., S. Aust., reef outer edge (Womersley, 5.i.1947; ADU, A4345). Port MacDonnell, S. Aust., in reef pools (Womersley, 29.i.1964; ADU, A27305). Point Bunbury, Apollo Bay, Vic., upper sublittoral (Womersley, 12.iv.1959; ADU, A22644). Hinders, Vic., upper sublittoral ( Womersley, 18.i.1967: ADU, A31786). Green Point, N,W. Tas., upper sublittoral deep pools ( Wollaston & Mitchell, 24.ii.1964; ADU, A27554).


Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: From Fishery Bay, Eyre Pen., S. Aust. to Flinders, Vic., and the N. and N.W. coast of Tasmania.

Taxonomic notes: While most specimens of D. nigricans are clearly distinct from D. muelleri in their densely clumped habit, in width of branches, thickness, and colour, some intergrades (e.g. A31786) do occur (Womersley 1967, p. 218). D. nigricans is characteristic of the uppermost sublittoral, especially in pools, on rough water coasts, and may cover extensive areas of rock.

References:

WOMERSLEY, H.B.S. (1949). Studies on the marine algae of southern Australia. No. 3. Notes on Dictyopteris Lamouroux. Trans. R. Soc. S. Aust. 73, 113–116, Plate 22.

WOMERSLEY, H.B.S. (1967). A critical survey of the marine algae of southern Australia. II. Phaeophyta. Aust. J. Bot. 15, 189–270.

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


Illustrations in Womersley Part II, 1997: FIGS 78C, 79K,L.

Figure 78 image

Figure 78   enlarge

Fig. 78. A. Dictyopteris acrostichoides (ADU, A55432). B. Dictyopteris muelleri (ADU, A31658). C. Dictyopteris nigricans (ADU, A2296, holotype).

Figure 79 image

Figure 79   enlarge

Fig. 79. A–D. Dictyopteris acrostichoides (ADU, A55432). A. Transverse section of edge of wing. B. Transverse section of mid wing. C. Tetrasporangial thallus showing broad sterile zone between sporangia and margin. D. Transverse section with undivided tetrasporangia. E–J. Dictyopteris muelleri (ADU, A57063). E. Transverse section of edge of wing. F. Transverse section of part of midrib and lateral wing with rhizoids on both sides of midrib. G. Tetrasporangial thallus with midrib and hair tufts. H. Transverse section of thallus with tetrasporangia and a phaeophycean hair tuft. I. Male thallus with antheridial sori and hair tufts. J. Transverse section of thallus with antheridia. K,L. Dictyopteris nigricans (ADU, A4345). K. Transverse section of wing from edge to a phaeophycean hair tuft. L. Transverse section with an undivided sporangium.


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