Electronic Flora of South Australia Species Fact Sheet

Myrionema incommodum Skottsberg 1907: 52, figs 56–60; 1921: 15, fig. 6d-h.

Phylum Phaeophyta – Order Chordariales – Family Myrionemataceae

Selected citations: Womersley 1967: 229.

Thallus medium brown, of radiating prostrate filaments more or less discrete or grouped, sometimes tending to be discoid, 200–300 µm long, epiphytic but inconspicuous on Adenocystis. Basal layer (Fig. I 7A) monostromatic, of more or less straight, occasionally branched, filaments with cells 6–12 µm long, 3–5 um broad and 3–5 µm high. Erect assimilatory filaments (Fig. 17B) slightly clavate, arising from every cell more than 6–12 cells from the ends of the basal filaments, 40–50 µm and 3–5 cells high, with cells (7–) 12–16 µm long and 4–8 µm in diameter; phaeoplasts few per cell. Hairs phaeophycean, scattered, with a basal meristem, 5–8 µm in diameter.

Reproduction: Plurilocular sporangia (Fig. 17B) elongate-ovoid, on 1–4 celled pedicels or lateral on erect filaments (Skottsberg 1921, fig. 6g,h), 20–35 µm long and 10–12 µm in diameter, uniseriate or partly biseriate. Unilocular sporangia (Fig. 17C) sessile on cells of the basal layer or lateral on the first cell of erect filaments, ovoid, 20–25 µm long and 12–20 µm in diameter.

Type from South Georgia, on Adenocystis; in UPS (?).

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

Distribution: Patagonia, Fuegia, Falkland Is., South Georgia.

In southern Australia, from Safety Cove, Port Arthur, Tas., mid eulittoral on Adenocystis (Skinner, 21.ii.1978; ADU, A50536; and Womersley & Parsons, 31.x.1982; ADU, A55952).

Taxonomic notes: The Tasmanian specimens have shorter assimilatory filaments and are generally smaller in dimensions than in Skottsberg's illustrations, and may be young plants or near the end of the distributional range of the species. They are quite inconspicuous on their host. Skottsberg (1921, p. 15) reported Kjellman to have found M. incommodum on Adenocystis from Port Arthur, Tasmania, and he also suspected that the illustrations of Harvey (1858, pl. 48 figs 3,4) might apply to this Myrionema and not to Adenocystis (where the sporangia are borne laterally at the base of single-celled assimilators.

References:

HARVEY, W.H. (1858). Phycologia Australica. Vol. I, Plates 1–60. (Reeve: London.)

SKOTTSBERG, C. (1907). Zur Kenntnis der Subantarktischen und Antarktischen Meeresalgen. I. Phaeophyceen. Wissenschaftliche ergebnisse der Schwedischen Südpolar-expedition 1901–1903, 4, 1–172, Plates 1–10.

SKOTTSBERG, C. (1921). Botanische Ergebnisse der Schwedischen Expedition nach Patagonien und dem Feuerlande, 1907–1909. VIII. Marine Algae. I. Phaeophyceae. K. Svenska Vetenskapsakad. Handl. 61(11), 1–56.

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: 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 A–C.

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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