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Electronic Flora of South Australia Species Fact Sheet

Austrolithon intumescens A. Harvey & Woelkerling 1995: 363, figs 1–41.

Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Austrolithoideae

Thallus largely unconsolidated, mostly 0.2–3.0 mm in greatest extent, endophytic except for conceptacle roofs and formed within gall-like deformities of host branches mostly less than 1 mm in greatest dimension. Structure partly filamentous and partly pseudoparenchymatous; construction diffuse, consisting of branched filaments with cells mostly 6–12 µm in diameter and 16–49 µm long; epithallial cells mostly 5–12 µm in diameter and 12–14 µm long, terminating most conceptacle roof filaments but absent from vegetative thallus, with outermost walls rounded or flattened but not flared; cell elongation characteristics uncertain; cell-fusions and secondary pit-connections absent; haustoria and trichocytes unknown.

Reproduction: Vegetative reproduction unknown. Gametangia and carposporophytes produced in largely endophytic uniporate conceptacles; tetrasporangia produced in largely endophytic multiporate conceptacles. Bisporangia unknown.

Gametangial thalli probably dioecious. Carpogonia terminating 2-celled filaments arising from the female conceptacle chamber floor. Mature female-carposporangial conceptacle roofs flush with or protruding above the host gall surface, 32–68 µm thick, composed of 2–5 layers of cells above the chamber, conceptacle chambers 59–145 µm in diameter and 67–115 µm high. Mature carposporophytes composed of a conspicuous central fusion cell and several-celled gonimoblast filaments bearing terminal carposporangia 13–24 µm in diameter. Both unbranched and branched spermatangial filaments present, arising from the floor, walls and roof of male conceptacle chambers, mature male conceptacle roofs flush with or protruding above the host gall surface, 19–49 µm thick, composed of 2–5 layers of cells above the chamber, conceptacle chambers 54–125 µm in diameter and 54–140 µm high.

Tetrasporangial conceptacle roofs flush with or protruding slightly above the host gall surface, 17–23 µm thick above the chamber and composed of two cell layers, conceptacle chambers 81–140 µm in diameter and 62–108 µm high; tetrasporangia scattered across the conceptacle chamber floor, each mature sporangium 12–19 µm in diameter and 57–65 µm long, containing zonately arranged tetraspores and possessing an apical plug that blocks a roof pore prior to spore release.

Type from Kitty Miller Bay, Phillip I., Vic., (Woelkerling, Campbell & Penrose, 2.xii.1985); holotype in LTB (15232); depicted in A. Harvey & Woelkerling (1995, p. 364, figs 1–4).

Selected specimens: St Francis I., Isles of St Francis, S. Aust., 0–2 m deep (Shepherd, 6.i.1971; AD, A63422 = LTB, 15300). Cape du Couedic, Kangaroo I., S. Aust., lower eulittoral (Womersley, 12.i.1948; AD, A63423 LTB, 17295). Cape Willoughby, Kangaroo I., S. Aust., drift (Womersley, 12.i.1947; AD, A63425 = LTB, 15301). Lawrence Rocks, Portland, Vic., 22 m deep (Watson, 20.xii.1982; AD, A63420 = LTB, 15298). Dinghy Cove, Lady Julia Percy I., Vic., 3–6 m deep (Shepherd, 4.i.1968; AD, A63424 = LTB, 15299). Kitty Miller Bay, Phillip I., Vic., on Haliptilon (Turner, 24.i.1979; LTB, 14764). Hunter I., Tas., in pools (Bennett, 14.i.1954; AD, A63421 = LTB, 15303).


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

Distribution: St Francis I., Isles of St Francis, S. Aust., to Kitty Miller Bay, Phillip I., Vic., and from Hunter I., Bass Strait, Tasmania.

Taxonomic notes: Austrolithon intumescens has been found only in the geniculate coralline Haliptilon roseum; host thalli containing the endophyte have been collected from intertidal pools and subtidally to depths of 22 m. A. intumescens causes irregularly shaped, swollen, gall-like deformities of host branches; galls can be readily detected on host specimens using a stereomicroscope. Apical plugs on tetrasporangia stain well with toluidine blue but not with potassium permanganate.

References:

HARVEY, A.S. & WOELKERLING, W.J. (1995). An account of Austrolithon intumescens gen. et sp. nov. and Boreolithon van-heurckii (Heydrich) gen. et comb. nov. (Austrolithoideae subfam. nov., Corallinaceae, Rhodophyta). Phycologia 34, 362–382.

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

Author: W.J. Woelkerling & A.S. Harvey

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


Illustrations in Womersley Part IIIA, 1996: FIGS 67, 68.

Figure 67 image

Figure 67   enlarge

Fig. 67. Austrolithon intumescens (A, LTB, 15299; B–E, LTB, 15232). A. Portion of host (Haliptilon roseum) with swollen, gall-like deformed branch tips (arrows) containing Austrolithon intumescens. B. Section of a gall-like deformity with thalli of Austrolithon intumescens. C. Thallus of Austrolithon intumescens embedded within the host. D. Section of mature tetrasporangial conceptacle (pore plugs not evident with permanganate staining). E. Portion of tetrasporangial conceptacle roof with darkly stained pore plugs blocking the pore canals (stained with toluidine blue).

Figure 68 image

Figure 68   enlarge

Fig. 68. Austrolithon intumescens (A, B, D, LTB, 15232; C, LTB, 14764). A. Surface view of multiporate tetrasporangial conceptacle largely embedded within gall-like deformity of host. B. Section of female-carposporangial conceptacle with mature carpogonial filaments (arrowheads) and trichogynes (arrows). C. Section of female-carposporangial conceptacle with mature carposporophyte. D. Section of male conceptacle with spermatangial filaments arising from chamber floor and walls.


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