Electronic Flora of South Australia Species Fact Sheet
Phylum Phaeophyta – Order Chordariales – Family Leathesiaceae
Thallus (Fig. 24D) forming spreading patches on the surface of Leathesia difformis, with endophytic basal filaments producing single or clustered, emergent, cortical filaments extending 100–200 µm beyond the host surface. Basal filaments branched, ramifying between the host cortical filaments, of somewhat irregular cells 4–8 p.m in diameter and L/B (1–) 2–3. Medulla virtually absent, with cortical filaments and hairs arising directly from basal filaments. Determinate cortical filaments (Fig. 24D) of fairly even height, simple, straight to slightly curved and almost cylindrical to slightly broader in their mid part, 120–200 µ and 8–14 cells long, 10–14 µ in greatest diameter with cells L/B (0.7–) 1–1.5 (–2); growth apical and intercalary. Phaeoplasts (Fig. 24E) several per cell, irregular in shape, usually with a pyrenoid. Phaeophycean hairs (Fig. 24D) frequent, arising from basal filaments, 10–14 (–16) µm in diameter and extending well beyond the cortex.
Reproduction: Unilocular sporangia (Fig. 24D) sessile or with a unicellular pedicel on basal filaments, largely within the host cortex, clavate to ovoid, 40–60 µm long and 12–20 (–25) µm in diameter.
Type from Aldinga, S. Aust., on Leathesia difformis, low eulittoral on rock platform (Skinner, 31.x.1978); holotype in ADU, A49777.
Distribution: Only known from the type.
Although only known from a single collection, Strepsithalia leathesiae appears distinct from other species in the relatively broad cortical filaments.
References: The Marine Benthic Flora of Southern Australia Part II
Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
Illustration in Womersley Part II, 1997: FIG. 24 D,E.
Figure 24 enlarge
Fig. 24. A–C. Strepsithalia liagorae (A,B, ADU, A49565; C, ADU, A54929). A. Thallus with determinate cortical filaments, phaeophycean hairs and unilocular sporangia arising from basal filaments. B. Cells of a determinate cortical filament, with phaeoplasts. C. Thallus with plurilocular sporangia, and phaeophycean hairs arising from erect or basal filaments. D,E. Strepsithalia leathesiae (ADU, A49777, holotype). D. Thallus with determinate cortical filaments, phaeophycean hairs and unilocular sporangia arising from basal filaments. E. Cells of a determinate cortical filament with phaeoplasts. F–H. Strepsithalia aemula (ADU, A49564, holotype). F. Thallus with branched determinate cortical filaments, phaeophycean hairs and unilocular sporangia arising from basal filaments. G. Cells of a determinate cortical filament, with phaeoplasts. H. Basal filament with a probable plurilocular sporangium. I–K. Acrotrichium amphibolis (ADU, A52820, holotype). I. Thallus (diagrammatic) on Amphibolis, showing basal filaments, medullary filaments, stratum of plurilocular sporangia, and determinate cortical filaments with some continuing as phaeophycean hairs. J. Ditto showing cell detail with central parts of cortical filaments omitted. K. Detail of plurilocular sporangia.
State Herbarium of South Australia