Electronic Flora of South Australia Family Fact Sheet

Phylum RHODOPHYTA Wettstein 1901: 46

Thallus microscopic (unicellular or filamentous) to macroscopic, a few millimetres to about a metre long, attached by a rhizoidal or cellular holdfast; epilithic or epiphytic, or rarely free-floating, annual or perennial. Habit filamentous to pseudoparenchymatous, or parenchymatous, cylindrical to flat or inflated and vesicular, or crustose, usually slightly to profusely branched. Colour usually red in deeper water species, sometimes pink (in Corallinales), often yellow to yellow-brown (bleached) in intertidal or shallow-water species, occasionally purple to almost black. Cells small and uninucleate to large (several mm long) and multinucleate, usually vacuolate. Cell wall of an inner layer of rigid cellulose (or related) microfibrils and an outer amorphous mucilaginous layer of sulphated galactan polymers (giving agar, carrageenan etc. in some genera), with a firm outermost proteinaceous pellicle (cuticle) in some taxa; some Bangiophyceae with an inner fibrillar xylan wall and outer non-fibrillar mannan wall, but with cellulose microfibrils in the conchocelis phase; CaCO3 as calcite in the Corallinales cell walls, as aragonite in some Nemaliales (e.g. Liagora). Cell division by ingrowth of cellulose wall material leaving a central aperture which becomes blocked by a pit-plug consisting of a central core of protein and outer polysaccharide layers; such pit-connections absent from gametophytic thalli of Bangiophyceae but present in the conchocelis phase of Bangiales. In many taxa secondary pit-connections connect adjacent cells of different filaments, or lie adjacent to primary connections, formed usually by a small cell derived from a thallus cell fusing with an adjacent cell, leaving a slender protoplasmic connection, or by direct cell fusions in Corallinaceae. Rhodoplasts single and stellate to numerous and discoid, with non-aggregated photosynthetic thylakoids, containing chlorophyll a (some taxa also with chlorophyll d), α and β carotene, several xanthophylls, and accessory photosynthetic phycobilins (phycoerythrin and phycocyanin) as granules on the surface of the thylakoids; phycoerythrin (red) usually predominant over the phycocyanin (blue-green); pyrenoids present in rhodoplasts of some primitive groups (Bangiophyceae, Nemaliales). Storage carbohydrate Floridean starch (an amylopectin, staining yellow to brown-purple with iodine), present as scattered granules in cytoplasm. Gland cells (vesicle cells) present in some taxa, with clear, highly refractive contents rich in bromine or iodine. Unicellular colourless hairs produced from cortical cells in many genera, and branched (rarely unbranched) usually colourless multicellular trichoblasts in many genera of Ceramiales. Growth diffuse in Bangiophyceae, usually apical and filamentous in Florideophyceae, with intercalary cell divisions in some taxa. Structure in Florideophyceae uniaxial or multiaxial and obviously filamentous to pseudoparenchymatous with closely to loosely associated filaments of elongate to globular cells.

Reproduction: Sexual reproduction oogamous, with female carpogonia usually borne as the terminal cell of a specialised carpogonial branch, and minute, non-motile, colourless spermatia, usually cut off as a surface cluster or layer. Zygote developing on the (female) gametophyte and producing carposporangia directly or via gonimoblast filaments, or via an auxiliary cell to which the diploid post-fertilization nucleus is passed and which then develops into a fusion cell which produces carposporangia directly or via gonimoblast filaments; carposporophyte attached to and partially parasitic on the female gametophyte. Carpospores producing an alternate isomorphic or heteromorphic phase, the tetrasporophyte, which in turn produces meiospores (tetraspores) in distinctive groups of four by meiotic divisions; bispores and polyspores formed in some genera. Monospores and paraspores present in some genera, non-meiotic.

Life history basically triphasic in most orders (monophasic or biphasic in some Bangiophyceae) with two dissimilar sporophyte generations, the carposporophyte attached to and partly parasitic on the female gametophyte and the free-living tetrasporophyte which is isomorphic or heteromorphic with the gametophytes.

Taxonomic notes: The phylum Rhodophyta is characterised by the presence of accessory photosynthetic pigments (the phycobilins phycoerythrin and phycocyanin) on non-aggregated thylakoids in the (usually) red rhodoplasts, the production of floridean starch as the reserve substance, and oogamous sexual reproduction involving female carpogonia and non-motile male spermatia; no flagellate cells occur in the phylum; the zygote is retained and develops on the parent gametophyte.

The Rhodophyta is a distinctive group with some 650–700 genera and over 4,000 species. Southern Australia is particularly rich, with some 284 genera and 800 species, many of the species being endemic. A general analysis of their biogeography is given in Part I (Womersley 1984, pp. 53–56) and in Womersley (1981).

A few southern Australian Rhodophyta are probably adventives from other regions. These include Solieria tenera, Schottera nicaeensis recorded by Lewis & Kraft (1979), Antithamnionella spirographidis by Wollaston (1968, p. 345), Cottoniella fusiformis (in Gulf St Vincent, S. Aust.), Polysiphonia brodiaei and P. pungens (= P. senticulosa Harvey) by Womersley (1979, pp. 496, 472 resp.)

The Rhodophyta in general have been reviewed by Dixon (1973), Dixon & Irvine (1977b), Gabrielson & Garbary (1986), Kraft (1981), Kraft & Woelkerling (1981, 1990) and Magne (1989), and their life-histories have been discussed by West & Hommersand (1981). While some orders (e.g. Rhodymeniales, Ceramiales) of the Rhodophyta are accepted by most phycologists, others are still in a state of flux. This applies in particular to Class Bangiophyceae (see Magne 1989), to the old order Nemaliales, from which several orders have been separated, and to the order Gigartinales. Orders separated from the Nemaliales include the largely marine order Acrochaetiales (see Papenfuss 1966; Garbary 1978), and the entirely marine Bonnemaisoniales (Feldmann & Feldmann 1942; Chihara & Yoshizaki 1972) and Galaxaurales (Chaetangiales) (Desikachary 1963; Papenfuss 1966; Huisman 1985, p. 416), of which the Acrochaetiales and Bonnemaisoniales are accepted here, following in particular the studies on pit-plugs by Pueschel & Cole (1982) and Pueschel (1989). The latter work also supports recognition of the order Gelidiales, which Dixon (1973, p. 251) suggested should be placed within the Nemaliales, and gives the basis for recognition of the order Hildenbrandiales. The orders Cryptonemiales and Gigartinales have long been recognised as clear cut for some families but not so for others. Recently Kraft & Robins (1985) have suggested that these two orders are not satisfactorily separated and should be merged, resulting in the very large order Gigartinales with over 40 families. As well as the features discussed by Kraft & Robins, further difficulties exist with regard to families placed in the Gigartinales (sensu stricto) but which form auxiliary cells only in reproductive nemathecia (e.g. Peyssonneliaceae, Polyidaceae) or in special short shoots (e.g. Phacelocarpaceae, Nizymeniaceae, Plocamiaceae), not existing as vegetative cells of the thallus. It thus seems preferable to follow Kraft & Robins' suggestion and combine the Cryptonemiales and Gigartinales under the latter name. The family Gracilariaceae has recently been separated as an order by Fredericq & Hommersand (1989).

The Corallinaceae, formerly placed in the Cryptonemiales, are now regarded by most authors as constituting a separate order, the Corallinales (see Silva & Johansen 1986).


CHIHARA, M. & YOSHIZAKI, M. (1972). Bonnemaisoniaceae: their gonimoblast development, life history and systematics. In Abbott, I.A. & Kurogi, M. (Eds), Contributions to the systematics of Benthic Marine Algae of the North Pacific, pp. 243–252. (Jap. Soc. Phycol.: Kobe.)

DESIKACHARY, T.V. (1963). Status of the order Chaetangiales (Rhodophyta). J. Indian Bot. Soc. 42A, 16–26.

DIXON, P.S. & IRVINE, L.M. (1977b). Seaweeds of the British Isles. Vol. 1, Rhodophyta. Part I, Introduction, Nemaliales, Gigartinales. [British Museum (N.H.): London.]

DIXON, P.S. (1973). Biology of the Rhodophyta. Univ. Reviews in Botany, Vol. 4. (Oliver & Boyd: Edinburgh.)

FELDMANN, J. & FELDMANN, G. (1942). Recherches sur les Bonnemaisoniacées et leur alternance de générations. Ann. Sci. Nat., 11 Sér. Bot., 3, 75–175.

FREDERICQ, S. & HOMMERSAND, M.H. (1989). Proposal of the Gracilariales ord. nov. (Rhodophyta) based on an analysis of the reproductive development of Gracilaria verrucosa. J. Phycol. 25, 213–227.

GABRIELSON, P.W. & GARBARY, D. (1986). Systematics of red algae (Rhodophyta). CRC Critical Reviews in Plant Sciences, Vol. 3, Issue 4, pp. 325–366.

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

HUISMAN, J.M. (1985). The Scinaia assemblage (Galaxauraceae, Rhodophyta): a re- appraisal. Phycologia 24, 403–418.

KRAFT, G.T. & ROBINS, P.A. (1985). Is the Order Cryptonemiales (Rhodophyta) defensible? Phycologia 24, 67–77.

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.)

KRAFT, G.T. (1981). Rhodophyta: morphology and classification. In Lobban, C.S. & Wynne, M.J. (Eds), The Biology of Seaweeds, Ch. 1, pp. 6–51. (Bot. Monogr. Vol. 17, Blackwell: Oxford.)

LEWIS, J.A. & KRAFT, G.T. (1979). Occurrence of a European red alga (Schottera nicaeensis) in southern Australian waters. J. Phycol. 15, 226–230.

MAGNE, F. (1989). Classification et phylogénie des Rhodophycées. Cryptogamie, Algol. 10, 101–115.

PAPENFUSS, G.F. (1966). A review of the present system of classification of the Florideophyceae. Phycologia 5, 247–255.

PUESCHEL, C.M. & COLE, K.M. (1982). Rhodophycean pit plugs: an ultrastructural survey with taxonomic implications. Amer. J. Bot. 69, 703–720.

PUESCHEL, C.M. (1989). An expanded survey of the ultrastructure of red algal pit plugs. J. Phycol. 25, 625–636.

SILVA, P.C. & JOHANSEN, H.W. (1986). A reappraisal of the order Corallinales (Rhodophyceae). Br. phycol. J. 21, 245–254.

WEST, J.A. & HOMMERSAND, M.H. (1981). Rhodophyta: Life Histories. In Lobban, C.S. & Wynne, M.J. (Eds), The Biology of Seaweeds, Ch. 4, pp. 133–193. (Bot. Monogr. Vol. 17, Blackwell: Oxford.)

WETTSTEIN, A. (1901). Handbuch der systematischen Botanik. (Leipzig & Vienna.)

WOLLASTON, E.M. (1968). Morphology and taxonomy of southern Australian genera of Crouanieae Schmitz (Ceramiaceae, Rhodophyta). Aust. J. Bot. 16, 217–417, Plates 1–10.

WOMERSLEY, H.B.S. (1979). Southern Australian species of Polysiphonia Greville (Rhodophyta). Aust. J. Bot. 27, 459–528.

WOMERSLEY, H.B.S. (1981). Biogeography of Australasian marine macroalgae. In Clayton, M.N. & King, R.J. (Eds), Marine Botany: an Australasian Perspective, Ch. 11, pp. 292–307. (Longman Cheshire: Melbourne.)

WOMERSLEY, H.B.S. (1984). The marine benthic flora of southern Australia. Part I. (Govt Printer: Adelaide.)

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.


1. Pit-connections absent (except in conchocelis phase); cell divisions intercalary, rarely apical; sexual reproduction unknown in most, when present with the zygote forming directly a small number of carpospores, without a distinctive carposporophyte; tetrasporangia absent


1. Pit-connections present and usually prominent; cell divisions apical (also intercalary in some taxa); sexual reproduction usually present with distinctive carpogonia and spermatia, with a carposporophyte present; tetrasporangia usually present


2. Thallus unicellular or colonial with cells in an irregular or pseudofilamentous arrangement in a gelatinous matrix; asexual reproduction by release of vegetative cells or by endospores; sexual reproduction unknown


2. Thallus filamentous to foliose, parenchymatous; sexual reproduction present or unknown


3. Thallus usually microscopic, crustose, filamentous or foliose, pit-connections absent; basal attachment rhizoids present or absent, or with a pulvinate base; asexual reproduction by monospores derived from the parent cell by unequal division of the cell by a curved wall; sexual reproduction unknown or doubtful


3. Thallus macroscopic, filamentous to foliose, becoming several to many cells thick or wide; heteromorphic with pit-connections present in the microscopic sporophyte (conchocelis phase) but not in the macroscopic gametophyte which has basal attachment rhizoids; asexual reproduction by monospores or aplanospores in both generations, formed from whole cells or from differentiated sporangia; sexual reproduction usually present, involving spermatia and carpogonia with direct production of carposporangia from the zygote


4. Thallus crustose, with or without erect branches; pit-plugs with a single cap layer; sexual reproduction unknown; tetrasporangia borne in conceptacles


4. Thallus usually erect, crustose in some taxa (e.g. some Corallinales and Peyssonneliaceae); pit-plugs with no to three cap layers; sexual reproduction usually present; tetrasporangia not borne in conceptacles (except in Corallinales)


5. Carposporophyte developed directly from the fertilized carpogonium with or without fusion with adjacent sterile cells, or from the hypogynous cell or their joint fusion cell


5. Carposporophyte developed from an auxiliary cell which is not a cell of the carpogonial branch


6. Thallus firm and cartilaginous, pseudoparenchymatous, with or without internal rhizines; gametophytes and tetrasporophyte isomorphic; pit-plugs with one cap layer; carposporophytes arising directly from fertilized carpogonium, with or without fusion with cells of adjacent sterile branches


6. Thallus microscopic to macroscopic, soft and mucoid to firm, rarely cartilaginous; pit-plugs with none or two cap layers; sporophyte and gametophyte isomorphic or (usually) heteromorphic; carposporophyte developing from either carpogonium or hypogynous cell without sterile filaments adjacent to carpogonium; clusters of small nurse cells absent


7. Thallus with internal rhizines in most species; carpogonia sessile on, or intercalary between, cortical cells; carposporophyte arising directly from fertilized carpogonium, usually with clusters of small nurse cells on adjacent cells


7. Thallus without internal rhizines; supporting cell bearing a 2-celled carpogonial branch and two sterile branches, cells of which fuse with the fertilized carpogonium which develops into a fusion cell from which the gonimoblast develops; nurse cells absent


8. Thallus minute (usually less than 1 cm high, several cm high in Camontagnea), tufted or largely prostrate, of discrete uniaxial filaments; rhodoplasts usually with pyrenoids; carpogonia sessile on vegetative cells, carposporophytes naked, few-celled


8. Thallus (gametophyte) macroscopic, usually over 2 cm high, uniaxial or multiaxial, soft and mucoid to firm; rhodoplasts with or without pyrenoids; carpogonia terminating 2–4-celled branches, carposporophytes many-celled, protected by cortical filaments or an involucral pericarp


9. Thallus (gametophyte) macroscopic, multiaxial, often soft and mucoid, sometimes firm; pericentral cells absent; gland cells absent; pit-plugs with 2 cap layers; carposporophyte without a distinct pericarp or with a filamentous involucre, arising directly from the zygote or its daughter cell


9. Thallus uniaxial, a few cells thick or broad, with the axial cells cutting off (usually) 3 pericentral cells; gland cells usually present; pit-plugs with no cap layers; carposporophyte with a well-developed cellular pericarp


10. Auxiliary cell normally cut off from the supporting cell after fertilization; pit-plugs with no cap layers


10. Auxiliary cell present before fertilization, either as a vegetative cell of the thallus or as a cell of a specialised filament; pit-plugs with no or two cap layers


11. Thallus usually very strongly calcified, with calcite deposited in the cell wall; intercalary meristem in vegetative filaments usually present; pit-plugs 2–1ayered with dome-shaped caps; tetrasporangia zonately divided usually with simultaneous division (cruciately divided in Sporolithon); reproductive structures usually borne in conceptacles; carpogonial branches 2-celled, borne on supporting cells which later act as auxiliary cells


11. Thallus not calcified (rarely superficially so or slightly internally, with aragonite); intercalary meristems absent; pit-plugs with no cap layers; tetrasporangia zonately or cruciately (rarely tetrahedrally) divided; reproductive structures not borne in conceptacles; carpogonial branches 2 to several cells long, with tubular or cellular connections between the fertilized carpogonium and the auxiliary cell


12. Auxiliary cell either in the vegetative thallus, in reproductive nemathecia, or in special fertile short shoots; diploidization via a tubular or cellular connection from the fertilized carpogonium to the auxiliary cell


12. Auxiliary cell the terminal cell of a 2-celled filament borne on the supporting cell of the carpogonial branch


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