Electronic Flora of South Australia Species Fact Sheet

Myriactula haydenii (Gatty) Levring 1937: 57.

Phylum Phaeophyta – Order Chordariales – Family Leathesiaceae

Selected citations: Kylin 1947: 49, fig. 42B.


Elachista haydenii Gatty 1863: 162.

Myriactis haydenii (Gatty) Batters. Kuckuck 1929: 37, figs 35,36.

Thallus (Fig. 25E,G) forming pulvinate to spreading, mucoid tufts, with endophytic basal filaments and dense medulla and cortex forming a layer 100–300 µm thick on the host. Basal filaments (Fig. 25E,G) penetrating between cells of host meristoderm and cortex and also growing within the ostioles (on Fucales), irregularly branched, with cells cylindrical to ovoid, mostly 6–8 µm in diameter and L/B 2–5. Medulla (Fig. 25E,G) of erect, clustered, branched colourless filaments, 30–80 µm and 3–6 cells long, cells ovoid, 10–15 (–20) µm in diameter and L/B 1–2, producing cortical filaments and phaeophycean hairs above. Determinate cortical filaments (Fig. 25E,G) of more or less similar height within a specimen, 80–150 (–240) µm and 4–10 (–16) cells long, simple, cylindrical to slightly clavate above their narrower base; lower cells 5–10 µm in diameter and L/B 2.5–5, mid and upper cells slightly swollen, 10–15 µm in diameter and L/B 1–1.5; apex of terminal cell rounded to slightly conical. Phaeoplasts (Fig. 25F) several per cell, discoid to elongate, each with 1 (–2) pyrenoid; upper cells usually (not always) with a dense mass of physodes (Fig. 25E,F). Phaeophycean hairs scattered, arising from upper medullary cells, 10–12(4 5) µm in diameter.

Reproduction: Plurilocular sporangia (Fig. 25E) borne on upper medullary cells, clustered, 50–90 (–125) µm and 8–16 locules long, 5–6 µm in diameter, uniseriate with occasional oblique walls. Unilocular sporangia (Fig. 25G) borne on branches of upper medullary filaments, clavate, 30–50 µm long and 12–20 Aim in diameter.

Type from Filey Bridge (Brig), Yorkshire, England (Hayden); in STA?

Selected specimens: Streaky Bay, S. Aust., on Caulocystis uvifera, lower eulittoral pools (Skinner & Gardiner, 30.xi.1977; ADU, A48881). Venus Bay, S. Aust., on Caulocystis in lower eulittoral pool (Skinner, 1.xii.1977; ADU, A48890). Stanley Beach, S. coast, Kangaroo I., S. Aust., drift on Myriodesma integrifolium (Womersley, 27.i.1957; ADU, A20836). Encounter Bay, S. Aust., on C. cephalornithos, lower eulittoral pools (Skinner, 23.xi.1977; ADU, A48860). Cape Lannes, S. Aust., on C. uvifera, lower eulittoral (Skinner, 11.ii.1979; ADU, A50269). Point Lonsdale, Vic., on Scytosiphon in lower eulittoral pool (Skinner, 4.i.1978; ADU, A49083). Queenscliff, Vic., on C. cephalornithos, lower eulittoral pools (Skinner, 4.i.1978; ADU, A49059). Low Head, Tas., on C. uvifera, lower eulittoral (Skinner, 23.ii.1978; ADU, A49168). Blackmans Bay, Tas., on C. cephalornithos, lower eulittoral (Skinner, 20.ii.1978, ADU, A49166).

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

Distribution: N. Europe, on various Scytosiphonales and Dictyosiphonales (Feldmann 1943, p.223).

In southern Australia, from Streaky Bay, S. Aust. to Queenscliff, Vic. and Tasmania.

Taxonomic notes: The Australian specimens here referred to Myriactula haydenii occur on the fucalean Caulocystis, Myriodesma and Sargassum, as well as on Scytosiphon and Colpomenia. They differ from M. arabica in having broader determinate cortical filaments, but need further study of their variation and comparisons with typical material of M. haydenii from Europe.


FELDMANN, J. (1943). Une nouvelle espèce de Myriactula parasite du Gracilaria armata J. Ag. Bull. Soc. Hist. Nat. Afr. Nord 34, 222–229.

GATTY, A. (1863). British Seaweeds. (Bell & Daldy: London.)

KUCKUCK, P. (1929). Fragmente einer Monographie des Pheosporeen. Biol. Anst. Helgol. 17, 1–93.

KYLIN, H. (1947). Die Phaeophyceen der Schwedischen Westkiiste. Acta Univ. lund. N.F. Avd. 2, 43(4), 1–99, Plates 1–18.

LEVRING, T. (1937). Zur kenntnis der Algenflora der norwegischen Westkiiste. Acta Univ. Lund. N.F. Avd. 2, 33(8), 1–148, Plates 1–4.

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

Author: H.B.S. Womersley & S. Skinner

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. 25 E–G.

Figure 25 image

Figure 25   enlarge

Fig. 25. A–D. Myriactula arabica (A,B, ADU, A48241; C,D, ADU, A33619). A. Thallus with basal filaments entering host, slight medulla, determinate cortical filaments, a phaeophycean hair and plurilocular sporangia. B. Short, lateral plurilocular sporangia on upper cells of a determinate cortical filament. C. Thallus with unilocular sporangia. D. Cells of determinate cortical filaments with phaeoplasts and physode masses. E–G. Myriactula haydenii (ADU, A48890). E. Thallus with basal filament penetrating host, slight medulla, determinate cortical filaments with physode masses, phaeophycean hairs and plurilocular sporangia. F. Cells of a determinate cortical filament with phaeoplasts and physode masses. G. Thallus with unilocular sporangia.

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