Electronic Flora of South Australia Family Fact Sheet

ORDER ACROCHAETIALES Feldmann 1953: 12

Phylum Rhodophyta – Class Florideophyceae

Thallus small (to 25 mm high) in Audouinella, to 5–20 cm high in Camontagnea, heterotrichous, uniaxial, ecorticate or corticate (in Camontagnea), usually branched, attached by a single cell or a multicellular prostrate system of discrete or associated (pseudoparenchymatous) filaments; erect filaments simple to much branched, monopodial, discrete, often tufted, hairs often present; indeterminate and determinate branches present in Camontagnea; in some species prostrate system more extensive than erect system; epilithic or on or in various other organisms, mostly marine. Cells of erect filaments more or less cylindrical to moniliform or irregular in shape, uninucleate; rhodoplasts parietal or axial, laminate to band shaped, spiral, stellate or discoid, one to several per cell, without or with one to several pyrenoids; pit-plugs 2–1ayered with a membrane as far as known. Growth of filaments normally apical.

Reproduction: Asexual monosporangia single or in clusters, produced in most species (often the only known means of reproduction), usually on the erect filaments; bisporangia formed in some species, and rarely apomeiotic tetrasporangia.

Sexual reproduction known in some species only, with thalli monoecious or dioecious. Carpogonia sessile on vegetative cells or on 1–2-celled stalks, rarely intercalary. Fertilized carpogonia giving rise either directly, or after dividing transversely or longitudinally, to a small, diploid, filamentous carposporophyte with terminal carposporangia, each with a single carpospore; auxiliary cells absent. Spermatangia borne singly or in clusters on the erect filaments, rarely also on the prostrate filaments, each liberating a spermatium.

Tetrasporophytes morphologically similar or dissimilar to the gametophytes, bearing cruciately divided (sometimes irregularly) tetrasporangia, normally meiotic.

Life history monophasic (bearing only monospores), or triphasic and dimorphic or trimorphic, rarely diphasic and dimorphic.

Type genus: Acrochaetium Nägeli in Nägeli & Cramer (1858, p. 532) [=Audouinella Bory (1823, p. 340)].

Taxonomic notes: The Acrochaetiales have commonly been classed as a family of the Nemaliales (e.g. Bold & Wynne 1985, p. 555), but they differ from the two families now remaining in the latter order in their uniaxial structure and in bearing sessile as well as stalked carpogonia. The Acrochaetiales have been reviewed recently by Garbary (1978), Woelkerling (1983) and Garbary & Gabrielson (1987) who discuss relationships with other orders and who support their recognition as an order, by Garbary (1987) who lists all described species of Audouinella, and by Silva (in Silva, Meñez & Moe 1987, p. 127) who discusses generic relationships. The order is usually regarded as the most primitive group of the Florideophyceae (e.g. Garbary & Gabrielson 1987).

The genus Camontagnea has recently been described by Pujals (1981) and placed in the Acrochaetiales largely due to the presence of stellate rhodoplasts with a central pyrenoid. In size, habit and presence of indeterminate and determinate branches Camontagnea differs significantly from all other Acrochaetiales.

The Acrochaetiales includes only one family.

References:

BOLD, H.C. & WYNNE, M.J. (1985). Introduction to the Algae: Structure and reproduction. 2nd Edn. (Prentice-Hall: New Jersey.)

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

FELDMANN, J. (1953). L'évolution des organes femelles chez les Floriaes. Int. Seaweed Symp. Proc. 1, 11–12.

GARBARY, D.J. & GABRIELSON, P.W. (1987). Acrochaetiales (Rhodophyta): Taxonomy and evolution. Cryptogamie, Algol. 8, 241–252.

GARBARY, D.J. (1978). On the phylogenetic relationships of the Acrochaetiaceae (Rhodophyta). Br. phycol. J. 13, 247–254.

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

NÄGELI, C. & CRAMER, C. (1858). Pflanzenphysiologische Untersuchungen. Vol. 2. Die Stärkekörner. (F. Schulthess: ZUrich.)

PUJALS, C. (1981). Identidad de "Ballia scoparia" (Hook.f. et Harv.)Harv. (Rhodophyta, Florideophycidae). Rev. Mus. Arg. Cienc. Nat. "B. Rivadavia", Bot. 6, 1–22.

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: 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.


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