Electronic Flora of South Australia Species Fact Sheet

4.  ; Myrionema ramulans Skinner & Womersley sp. nov.

Phylum Phaeophyta – Order Chordariales – Family Myrionemataceae

Thallus dark brown, forming inconspicuous, more or less regular discs 0.5–5 mm across, epiphytic on species of Sargassum, Caulocystis and Cystophora. Basal layer (Fig. 17D) of subdichotomous, closely adjacent, radiating filaments with cells 7–15 (–20) µm long, 5–7 um broad and 3–7 µm high, each cell with several phaeoplasts and producing one or often two erect filaments. Erect assimilatory filaments (Fig. 17E, F) of similar height, 40–50 µm and (2–) 4–8(4 0) cells long, cylindrical, often branched, 2–4 µm in diameter, and each cell with 2–4 phaeoplasts; in some filaments the terminal cell has brown, even contents and resembles an ascocyst. Hairs phaeophycean, with a 3–4 celled pedicel below the meristem (lying at or just above the height of the erect filaments), 0.5–1.0 µm long and 5–8 µm in diameter.

Reproduction: Plurilocular sporangia (Fig. 17E) filiform, largely uniseriate with 6–10 locules, (20–) 25–35 µm long and 3–4 µm in diameter with a 1–2 celled pedicel, often branched and sporangia clustered, or lateral on erect filaments. Unilocular sporangia (Fig. 17F) sessile or on a unicellular pedicel from the basal layer cells, clavate, 20–30 µm long and 6–10 µm in diameter.

Type from Queenscliff, Vic., on Sargassum basal laterals, in upper sublittoral pools (Skinner, 4.i.1978); holotype in ADU, A49058.

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

Distribution: Known only from the type and Lady Bay, Normanville, S. Aust., on Sargassum in lower eulittoral pools (Skinner, 14.ix.1977; ADU, A48246). Pennington Bay, Kangaroo I., S. Aust., on Sargassum in sublittoral fringe (Woelkerling, 17.xi.1967; ADU, A32185). Point Lonsdale, Vic., on Sargassum, lower eulittoral (Skinner, 4.i.1978; ADU, A49065) and on Caulocystis cephalornithos, mid eulittoral pool (Skinner, 4.i.1978; ADU, A49066). Eastern Beach, Low Head, Tas., on Cystophora retroflexa (Skinner, 23.ii.1978; ADU, A49163).

Taxonomic notes: Myrionema ramulans, named for the frequently branched erect assimilatory filaments, is similar to M. furcatum Jaasund (1951, p. 133, fig. 3), but differs in having slenderer erect filaments and more filiform, slenderer, plurilocular sporangia.

References:

JAASUND, E. (1951). Marine algae from northern Norway. I. Bot. Not. 2, 128–142.

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

Author: S. Skinner & 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

Illustration in Womersley Part II, 1997: FIG. 17 D–F.

Figure 17   enlarge

Fig. 17. A–C. Myrionema incommodum (ADU, A55952). A. Margin of basal layer, with young erect filaments from older cells. B. Radial section showing erect assimilatory filaments (with phaeoplasts in some cells), a phaeophycean hair and plurilocular sporangia. C. Radial section with erect assimilatory filaments, a phaeophycean hair and unilocular sporangia. D–F. Myrionema ramulans (ADU, A49058, holotype). D. Margin of basal layer, with young erect filaments from older cells. E. Radial section with erect assimilatory filaments, a phaeophycean hair and plurilocular sporangia. F. Radial section with erect assimilatory filaments, phaeophycean hairs and unilocular sporangia.

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