Electronic Flora of South Australia Genus Fact Sheet

Genus AUDOUINELLA Bory 1823: 340, nom. cons.

Phylum Rhodophyta – Class Florideophyceae – Order Acrochaetiales – Family Acrochaetiaceae

Thallus epilithic or on or in a variety of organisms, attached by a single basal cell or a prostrate system of branched, discrete or laterally adherent, filaments. Erect filaments developed to varying extents, uniaxial, simple or branched, up to a few mm long. Cells cylindrical to irregularly swollen, containing one to several laminate, lobed, spiral, stellate or discoid rhodoplasts, usually parietal, with or without pyrenoids. Hairs often present. Growth normally apical.

Reproduction: Asexual monosporangia present in most species, sessile or stalked, usually borne on the erect filaments; bisporangia or apomeiotic tetrasporangia present in some species.

Sexual thalli (where known) monoecious or dioecious. Carpogonia sessile or on 1–2-celled stalks, solitary or in small groups, rarely intercalary. Fertilized carpogonia giving rise either directly or after dividing to a minute filamentous carposporophyte with terminal carposporangia. Spermatangia borne singly or in clusters, usually on the erect filaments.

Tetrasporophytes usually similar to gametophytes, bearing regularly or irregularly cruciately divided tetrasporangia.

Life history monophasic or triphasic (di- or trimorphic), rarely diphasic and dimorphic.

Lectotype species: A. miniata Bory 1823: 341 [=A. hermannii (Roth) Duby 1830: 972].

Taxonomic notes: This account of the southern Australian species revises that of Woelkerling (1971), with some nomenclatural changes and a re-ordering of the key; some doubtful records (e.g. those of Stegenga 1985, p. 328) are listed below under "Species Inquirendae". There has been no published account of the southern Australian species since 1971, but there is need for further morphological, life history, reproduction and cultural studies on many species, especially those which are at least partly endophytic (see Garbary 1979a, who raises doubts on species concepts based on host identity). Such studies will probably lead to a reduction in the number of species recognised here.

Whereas Woelkerling (1971) recognised two genera, Audouinella Bory for species with known sexual reproduction and Colaconema Batters (as a form genus) for those known to reproduce only by monospores, they are treated below under the one genus Audouinella. Earlier authors (see Woelkerling 1983; Garbary 1987; Lee & Lee 1988) have usually recognised 3–8 genera in the family, and Stegenga & van Erp (1979) consider that on the basis of life-history studies several genera should be recognised. In a recent review of carposporophyte development, Abdel-Rahman & Magne (1990) recognised 9 different types and considered that such an unstable carposporophyte does not provide useful taxonomic criteria. Such studies on southern Australian taxa are needed. The present account is based on our limited knowledge of life history and reproduction of many of the presumed species, especially those which live partially or largely within other organisms. The use of substrate-related characters in the key is only intended to facilitate identification, and colour is given for the larger or denser species only.

References:

ABDEL-RAHMAN, M.H. & MAGNE, F. (1990). Variation du carposporophyte chez les Acrochaetiales (Rhodophyta). Cryptogamie, Algol. 11, 23–30.

BORY DE ST-VINCENT, J.B. (1823). Audouinella. Dict. Class. d'Hist. Nat. 3, 340–341.

DUBY, J.E. (1830). Botanicon Gallicum seu Synopsis Plantarum in Flora Gallica Descriptarum. Part 2, Plantas Cellulares continens. Edn 2. (Paris.)

GARBARY, D.J. (1979a). A revised species concept for endophytic and endozoic members of the Acrochaetiaceae (Rhodophyta). Bot. Notiser 132, 451–455.

GARBARY, D.J. (1987). The Acrochaetiaceae (Rhodophyta): An annotated bibliography. Bibl. Phycol. 77, 1–267.

LEE, Y.P. & LEE, I.K. (1988). Contribution to the generic classification of the Rhodochortonaceae (Rhodophyta, Nemaliales). Bot. Mar. 31, 119–131.

STEGENGA, H. & VAN ERP, N.D. (1979). Morphological variation in the genus Acrochaetium (Rhodophyta, Nemaliales). Acta Bot. Neerl. 28, 425–448.

STEGENGA, H. (1985). The marine Acrochaetiaceae (Rhodophyta) of southern Africa. S. Afr. J. Bot. 51, 291–330.

WOELKERLING, W.J. (1971). Morphology and taxonomy of the Audouinella complex (Rhodophyta) in southern Australia. Aust. J. Bot. Suppl. 1, 1–91.

WOELKERLING, W.J. (1983). The Audouinella (Acrochaetium-Rhodochorton) complex (Rhodophyta): present perspectives. Phycologia 22, 59–92.

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

Author: W.J. Woelkerling & 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.

KEY TO SPECIES OF AUDOUINELLA

1. Thallus epilithic or entirely or largely epiphytic (with endophytic base only)

2

1. Thallus entirely or largely endophytic or endozoic

16

2. Thallus epilithic, usually 10–20 mm high, filaments 15–30 µm in diameter, cells with 3–10 parietal, more or less stellate, rhodoplasts each with a single pyrenoid

A. floridula

2. Thallus epiphytic, usually less than 10 mm high, filaments (3–) 6–20 (–25) µm in diameter, cells with one to a few laminate, ribbon shaped to irregular or discoid rhodoplasts with or without pyrenoids

3

3. Thallus (1–) 2–8 mm high

4

3. Thallus usually less than 1 mm high

10

4. Erect filaments mostly 3–10 µm in diameter

5

4. Erect filaments mostly 10–25 µm in diameter

7

5. Erect filaments much branched

A. saviana

5. Erect filaments simple to sparingly branched

6

6. Erect filaments (4–) 6–8 (–10) µm in diameter; rhodoplasts with one pyrenoid; monosporangia 9–15 µm in diameter and 18–24 µm long

A. secundata

6. Erect filaments 3–6 µm in diameter; rhodoplasts without a pyrenoid; monosporangia 5–7 (–10) µm in diameter and 8–15 (–18) µm long

A. simplex

7. Rhodoplasts parietal, band shaped, with a single, usually prominent pyrenoid

8

7. Rhodoplasts single or several closely adjacent, parietal, lobed, with (1–) 2–8 (–18) pyrenoids per cell

9

8. Monosporangia in clusters, on branched stalks, usually on lowermost cells of laterals

A. daviesii

8. Monosporangia sessile or occasionally stalked, solitary, senate or more scattered, with the apical wall often distinctly thickened

A. phacelorhiza

9. Epiphytic on Dictyotaceae; erect filaments usually 12–15 µm in diameter, rhodoplasts with 1–4 pyrenoids; carposporophytes with 3–10 carposporangia

A. dictyotae

9. Epiphytic on a wide variety of algae; erect filaments usually 15–20 µm in diameter, rhodoplasts several but closely adjacent and appearing single, cells with 2–8 (–18) pyrenoids; carposporophytes with 12–25 carposporangia

A. caespitosa

10. Thallus with erect filaments 200–1000 µm high

11

10. Thallus largely prostrate with erect filaments usually less than 200 µm high

12

11. Monosporangia more or less distichously arranged, laterals and erect filaments (6–) 8–11 (–17) 1 µm in diameter

A. plumosa

11. Monosporangia irregularly radially arranged, laterals and erect filaments 4–7 (–12) µm in diameter

A. pacifica

12. Erect filaments arising from a single cell (the original spore)

13

12. Erect filaments arising from a small, irregular, pseudoparenchymatous prostrate base

15

13. Cells 5–25 µm long, L/D 1–5

A. unifila

13. Cells 3–12 µm long, L/D usually 0.7–1.5

14

14. Basal cell with 1–3 (–4) erect, commonly curved, filaments, 3–12 µm in diameter

A. microscopica

14. Basal cells usually with a single straight filament, 3–5 µm in diameter

A. nakamurae

15. Thallus to 30 µm high, with erect filaments simple and 2–5 cells high

A. macula

15. Thallus 40–75 (–225) µm high, with erect filaments simple or branched and usually 5–15 cells long

A. humilis

16. Thallus endozoic in sponge skeletons

A. spongicola

16. Thallus occurring endophytically in various algae

17

17. Prostrate and erect systems both well developed (but see also A. liagorae and A. porphyrae), erect filaments normally 100–800 µm long with cells more than 20 µm high

18

17. Prostrate system well developed with irregular cells (in often contorted filaments), with only very short erect filaments usually less than 100 µm long (to 400 µm in A. liagorae) with cells less than 20 µm long

21

18. Prostrate filaments slenderer than erect filaments

A. blumii

18. Prostrate and erect filaments of similar diameter or the former greater

19

19. Sporangium-bearing erect filaments usually in fascicles, erect filaments mostly 10–18 µm in diameter, prostrate filaments (12–) 18–24 (–36) µm in diameter; rhodoplasts becoming highly dissected

A. polyidis

19. Sporangium-bearing erect filaments simple or irregularly branched, not fasciculate; filaments usually 4–10 µm in diameter; rhodoplasts laminate, not dissected

20

20. Cells of erect filaments of similar length throughout, L/D 3–5,7–10 (–18) µm in diameter, prostrate filaments more or less straight

A. barbadensis

20. Cells of erect filaments much longer above, L/D 5–10, 4–7 µm in diameter; prostrate filaments within host curved to reflexed

A. repens

21. Monosporangia 10–14 (–18) µm in diameter and 13–24 (–35) µm long; occurring in Liagora and Helminthocladia

A. liagorae

21. Monosporangia 6–12 µm in diameter and 8–14 µm long; occurring in Porphyra, or in Bonnemaisonia and Delisea

22

22. Monosporangia ovoid, terminal or lateral on erect filaments, occasionally sessile and broad-based on prostrate filaments; cells with rhodoplasts becoming stellate; occurring in Porphyra

A. porphyrae

22. Monosporangia broad-based, often hemispherical, borne on the side of prostrate filaments; cells with laminate rhodoplasts; occurring in Bonnemaisonia and Delisea

 23. A. bonnemaisoniae


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