Electronic Flora of South Australia Genus Fact Sheet

Genus MYRIONEMA Greville 1827: pl. 300

Phylum Phaeophyta – Order Chordariales – Family Myrionemataceae

Thallus (sporophyte) minute, 0.5–5 mm across, discoid or of grouped, radiating filaments, epiphytic. Basal layer monostromatic, of radiating filaments with each cell (except those near the margin) producing one or two short, erect, free filament(s) of equal height, or a reproductive organ or a hair. Growth largely apical. Gametophyte of branched filaments.

Reproduction: Reproduction by meiospores (which may act as gametes) from unilocular sporangia and by zoospores from neutral, uniseriate (occasionally biseriate), plurilocular sporangia on the discoid sporophyte, and by isogametes from plurilocular gametangia on the gametophyte.

Life history heteromorphic or direct.

Type species: M. strangulans Greville.

Taxonomic notes: A genus of numerous species, often not well known as to their life histories. Five species can now be recorded for southern Australia, and others are likely to occur. However, some may well be stages in life histories of other taxa of Chordariales (Pedersen 1984, p. 68), but they are described under Myrionema below to permit their recognition.

References:

GREVILLE, R.K. (1827). Scottish Cryptogamic Flora. Vol. 5, Plates 271–300. (Edinburgh.)

PEDERSEN, P.M. (1984). Studies on primitive brown algae (Fucophyceae). Opera Bot. 74, 1–76.

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

KEY TO SPECIES OF MYRIONEMA

1. Thallus forming brown, more or less circular, discs on Ulvales or the seagrass Zostera, contrasting with the host colour

2

1. Thallus forming irregular patches or discs on larger brown algae, not contrasting with the host

3

2. Epiphytic on Ulva or Enteromorpha; discs adhering to host throughout; ascocysts absent; hairs (7–) 8–12 µm in diameter 1

M. strangulans

2. Epiphytic on Zostera; discs becoming domed as their central part separates from host surface; ascocysts present, elongate, overtopping the 3–5 celled erect filaments in the central part of the disc; hairs 14–20 µm in diameter

M. latipilosum

3. Epiphytic on Adenocystis, forming irregular patches with the radiating basal filaments usually separate; erect filaments single from most basal cells, 4–7 cells long

M. incommodum

3. Epiphytic on Fucales; erect filaments often arising in pairs from each cell of basal layer, usually 5–15 cells long

4

4. Epiphytic on Caulocystis, Cystophora and Sargassum, more or less discoid, with erect filaments usually 4–8 cells long and often branched; hairs with their meristem 3–4 cells above their base

M. ramulans

4. Epiphytic on Myriodesma calophyllum, forming irregular discs with erect filaments of two heights, intermixed, the longer of 9–15 cells and the shorter of 4–5 cells; hairs with their meristem 5–11 cells above their base

M. myriodesmae


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