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4. Hildenbrandia expansa Womersley, sp. nov.

Phylum Rhodophyta – Class Florideophyceae – Order Hildenbrandiales – Family Hildenbrandiaceae

Thallus medium to dark red-brown, sometimes yellowish, covering extensive areas of smooth rock (5–20 cm across in the type and to 80 cm across in A60083), tightly adherent; surface smooth, thallus (250–) 400–700 (–800) µm thick. Structure (Figs 42D, 43D). Basal layer (becoming several cells thick) of irregularly radiating branched filaments, cells 4–7 µm diameter and L/D 1–2 (–2.5), each upper cell producing 1–2 erect filaments, mostly simple and laterally closely coherent, of small, cuboidal to slightly elongate, angular cells 3–5 µm in diameter and 3–6 µm long, with horizontal to inclined layers (Figs 42D, 43D) of clearer cells 8–10 µm long alternating with 2–4 layers of shorter cells, possibly indicating growth periods. Rhodoplasts small, central in each cell.

Reproduction: Conceptacles (Figs 42D, 43D) subspherical to ovoid, 40–60 1..tm in diameter and 80–120 1.1m long, with an ostiole 25–40 across; tetrasporangia 7–10 µm in diameter and 20–30 i_tm long, zonately divided with almost transverse cross walls; paraphyses abundant, 3–5 cells and 6–10 µm long, 2–3 [tm in diameter.

Type from Apollo Bay, Vic., in low eulittoral and uppermost sublittoral pools, shaded, on the S side of Point Bunbury (Womersley, 6.ii.1990); in AD, A60088.

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

Distribution: Apollo Bay to Cape Woolamai, Vic., and Southport, Tas.

Taxonomic notes: The Hildenbrandia from Victoria illustrated by Kraft & Woelkerling (1981, fig. 4.10E; 1990, fig. 3.11E) is clearly this species.

Denizot (1968, p. 198) records three species with zonate tetrasporangia having transverse walls; H. lecannellieri Hariot from the subantarctic (see above), H. occidentalis Setchell from Pacific N. America, and H. canariensis Boergesen from the Canary Islands; varieties of the latter two are known from other regions. H. lecannellieri is markedly different in form from H. expansa, and H. occidentalis and H. canariensis differ in not having paraphyses in the tetrasporangial conceptacles. H. expansa also covers much larger areas and is characterised by the inclined layers of larger cells within the thallus. A further species, H. dawsonii (Ardré) Hollenberg (1971, p. 286) from Pacific N. America, differs in having long, slender, apparently non-cellular paraphyses.


DENIZOT, M. (1968). Les Algues Floridées encroûtantes (a l'exclusion des Corallinacées). (Paris.)

HOLLENBERG, G.J. (1971). Phycological notes. VI. New records, new combinations, and noteworthy observations concerning marine algae of California. Phycologia 10, 281–289.

KRAFT, G.T. & WOELKERLING, W.J. (1981). Rhodophyta - systematics and biology. In Clayton, M.N. & King, R.J. (Eds), Marine Botany: an Australasian Perspective, Ch. 5, pp. 104–137. (Longman Cheshire: Melbourne.)

KRAFT, G.T. & WOELKERLING, W.I. (1990). Rhodophyta. In Clayton, M.N. & King, R.J. (Eds), Biology of Marine Plants, Ch. 3, pp. 41–85. (Longman Cheshire: Melbourne.)

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustrations in Womersley Part IIIA, 1994: PLATE 3 fig. 1; FIGS 42D, 43D.

Plate 3 image

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PLATE 3 fig. 1. Hildenbrandia expansa at Point Bunbury, Apollo Bay, Vic. (AD, A60088). fig. 2. Sonderopelta coriacea at Erith I., Bass Strait (AD, A45218). Photo: S.A. Shepherd. fig. 3. Halymenia plana at West I., S. Aust. (AD, A42902). Photo: K. Branden. fig. 4. Codiophyllum flabelliforme at Breaksea I., Albany, W. Aust. (in Murdoch). Photo: J.M. Huisman.

Figure 42 image

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Fig. 42. A. Hildenbrandia rubra (AD, A60783). Cross section of thallus with a conceptacle and irregularly divided tetrasporangia. B. Hildenbrandia crouanii (AD, Al2966). Cross section of thallus with a conceptacle with tetrasporangia divided by obliquely zonate walls. C. Hildenbrandia lecannellieri (AD, Al2986). Cross section of thallus and conceptacle (in part) with zonately and irregularly divided tetrasporangia. D. Hildenbrandia expansa (AD, A60088). Cross section of thallus and conceptacle (in part) showing regular horizontal and vertical rows of cells, with horizontal layers of larger cells (arrows), and zonately divided tetrasporangia with paraphyses. E–H. Rhodopeltis australis (E, AD, A15518; F, AD, A8320; G, AD, A34997; H, AD, A38735). E. Section of female nemathecium with a carpogonial branch and an auxiliary cell branch among paraphyses. F. Section of a female nemathecium with a carposporophyte borne on an auxiliary cell. G. Section of a male nemathecium with spermatangial branches. H. Section of outer cortex (with inner stellate cells) with tetrasporangia among short paraphyses.

Figure 43 image

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Fig. 43. A–C. Hildenbrandia lecannellieri (AD, Al2986). A. Thallus, showing surface with verrucose to tuberculate excrescences. B. Cross section of thallus with an area (darker) of slightly separated rows of older cells. C. Cross section of thallus with conceptacles. D. Hildenbrandia expansa (AD, A60088). Cross section of thallus showing horizontal layers of cells and conceptacles.

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