Electronic Flora of South Australia Family Fact Sheet

ORDER GIGARTINALES Schmitz in Engler 1892: 18, emend. Kraft & Robins 1985: 75

Phylum Rhodophyta – Class Florideophyceae

Thallus macroscopic, crustose or erect and frondose to much branched, a few taxa minute and parasitic; branches terete to compressed or flat, not calcified (with very few exceptions), cartilaginous to mucilaginous. Structure uniaxial or multiaxial, loosely filamentous to pseudo-parenchymatous. Cells varying in shape, uni- to multinucleate; rhodoplasts discoid, numerous per cell, without pyrenoids; pit-plugs without cap layers. Growth of branches and filaments apical.

Reproduction: Sexual thalli monoecious or dioecious; procarpic or non-procarpic. Carpogonial branches usually situated on inner cortical cells, 3 to several cells long, straight or curved, inwardly or outwardly projecting, with the supporting cell mono- or polycarpogonial, with one or more connecting filaments from the fertilized carpogonium or other cells after fusion. Auxiliary cells in special accessory systems or branches or transformed from ordinary vegetative cells. Carposporophytes within the cortex, in protuberant cystocarps, or in surface nemathecia, with or without a filamentous enveloping tissue or pericarp. Spermatangia cut off from surface cortical cells.

Tetrasporophytes crustose or erect, tetrasporangia derived from cortical cells or within nemathecia, usually terminal but intercalary in a few taxa, cruciately, zonately or irregularly divided.

Life history usually triphasic, with isomorphic or heteromorphic gametophytes and tetrasporophytes.

Taxonomic notes: The Gigartinales is now considered to include the Cryptonemiales, as advocated by Kraft & Robins (1985) who have shown that separation of the Cryptonemiales as having auxiliary cells in accessory systems within the thallus, in contrast to transformation of vegetative cells into auxiliary cells in the Gigartinales, is not satisfactory. There are also several families of the older Gigartinales which vary from this definition, e.g. Polyidaceae and Peyssonneliaceae where the auxiliary cells are only formed in special reproductive nemathecia, and families such as the Plocamiaceae, Phacelocarpaceae and Nizymeniaceae where auxiliary cells (and carpogonial branches) are formed in special short shoots in branch axils or on the surface, and are not present on or in sterile thalli. This results in a very large order of some 40 families, and keying and identification within the order is far from easy without detailed studies on good reproductive material. Many of the families however have a highly distinctive female reproductive system from which they can be recognised. Taxa which have recently been separated as orders include the Corallinales by Silva & Johansen (1986), the Ahnfeltiales (not known in Australia) by Maggs & Pueschel (1989, p. 349) and the Gracilariales by Fredericq & Hommersand (1989, p. 225).

References:

ENGLER, A. (1892). Syllabus der Vorlesungen über specielle and medicinisch-pharmaceutische Botanik ... Grosse Ausgabe. (Borntraeger: Berlin.)

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.

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

MAGGS, C.A. & PUESCHEL, C.M. (1989). Morphology and development of Ahnfeltia plicata (Rhodophyta): proposal of Ahnfeltiales ord. nov. J. Phycol. 25, 333–351.

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

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.

KEY TO FAMILIES OF GIGARTINALES

1. Thallus more or less prostrate, or erect, segmented and heavily calcified; sexual (and usually tetrasporangial) reproduction within special surface nemathecia

2

1. Thallus generally erect, simple and foliose to much branched, with a small basal holdfast, in a few taxa minute and parasitic; structure filamentous, loosely compacted, sometimes pseudoparenchymatous; carposporophytes usually within filamentous involucres or pericarp walls, swelling the thallus or forming globular cystocarps; tetrasporangia scattered or in sori, within the outer cortex

3

2. Thallus prostrate, orbicular to lobed or variously divided in a horizontal plane, not segmented, closely adherent to largely free from the substratum, attached by rhizoids from a basal layer of radiating filaments or the ends of downwardly assurgent filaments; with or without internal calcification; basal or mid filaments producing simple or branched, erect or assurgent filaments with apical growth. Reproduction (sexual and tetrasporangial) in superficial nemathecia on the thallus surface

PEYSSONNELIACEAE

2. Thallus erect, segmented, internodes flat and heavily calcified, with surface nemathecia when reproductive

POLYIDACEAE

3. Auxiliary cells terminal or intercalary in special branches arising laterally from inner cortical or outer medullary cells

4

3. Auxiliary cells transformed from ordinary vegetative cells of the thallus, or from vegetative cells in special reproductive short shoots formed on the thallus surface

6

4. Carpogonial branches (2–4-celled) and auxiliary cells in accessory ampullae of short, sterile filaments within the cortex; non-procarpic

HALYMENIACEAE

4. Carpogonial branches (3–10 cells long) and auxiliary cell branches accessory within the cortex but not within ampullae

5

5. Non-procarpic. Carpogonial branches single, carpogonia terminal on curved 5–10-celled branches, auxiliary cells 1–4 cells from the end of 5–12-celled auxiliary cell branches; fertilized carpogonium connecting with a subterminal cell of the carpogonial branch, then producing connecting filaments which fuse with auxiliary cells prior to formation of carposporophytes; tetrasporangia zonately or cruciately divided

DUMONTIACEAE

5. Procarpic or non-procarpic. Carpogonial branches one to several per supporting cell, carpogonia terminal on 3-celled branches, with characteristic, usually lobed, basal and hypogynous cells; connecting filaments present (except in Callophyllis); auxiliary cell groups usually distinct, with the basal auxiliary cell bearing several subsidiary cells, or the supporting cell acting as the auxiliary cell; carposporophyte developing from the auxiliary cell or from the adjacent connecting filament; tetrasporangia cruciately divided

KALLYMENIACEAE

6. Thallus multiaxial, erect (a few taxa with a crustose tetrasporophyte) or parasitic and pulvinate

7

6. Thallus uniaxial, erect or parasitic and pulvinate

13

7. Thallus pseudoparenchymatous and of uniform ovoid cells, or with a lax filamentous medulla of elongate cells; tetrasporangia cruciately divided (zonate in crustose phase of Schizymenia)

8

7. Thallus usually with a lax to dense filamentous medulla of elongate cells and a cortex of ovoid cells or anticlinal filaments; tetrasporangia zonately divided

10

8. Thallus pseudoparenchymatous throughout; tetrasporangia formed in chains in nemathecia or pustules

PHYLLOPHORACEAE

8. Thallus with a lax medulla of filaments of elongate cells; tetrasporangia scattered or in small subsurface sori

9

9. Thallus soft, often gelatinous; cortical filaments in discrete branch systems without secondary pit-connections; non-procarpic with separate supporting and auxiliary cells; all cells of gonimoblast filaments forming carposporangia; pericarp absent or slight; tetrasporangia scattered (zonate and terminal on filaments of crustose sporophyte in Schizymenia)

NEMASTOMATACEAE

9. Thallus firm; cortical filaments with secondary pit-connections; procarpic with the supporting cell acting as the auxiliary cell; carposporophyte with small groups of carposporangia within a filamentous matrix, with enveloping tissue usually present; tetrasporangia in small subsurface sori

GIGARTINACEAE

10. Carpogonial branches directed outwards with relatively straight trichogynes

11

10. Carpogonial branches directed inwards, with reflexed trichogynes

12

11. Carpogonial branches usually curved laterally, fusion cell with a single, outwardly directed gonimoblast initial; carposporophyte with a narrow base and the cystocarp cavity floor often lined with darkly staining nutritive tissue, with downward growing nutritive filaments from the gonimoblasts to the cystocarp floor; carposporophyte without early admixture of gonimoblast and vegetative cells; spermatangia in surface sori, cut off from outer cortical cells

SARCODIACEAE

11. Carpogonial branches usually straight, fusion cell with multiple gonimoblasts; carposporophyte with a reticulate persistent fusion cell composed of auxiliary cell and adjacent gametophytic cells; spermatangia in isolated, sunken, clusters in the outer cortex

DICRANEMATACEAE

12. Non-procarpic, with connecting filaments between (often distant) carpogonia and auxiliary cells; carposporophyte with a large central fusion cell or a placenta of intermixed gametophytic and carposporophytic cells, with outwardly radiating gonimoblasts bearing single rows or clusters of carposporangia; spermatangia clustered on surface cortical cells

ARESCHOUGIACEAE

12. Procarpic; gonimoblasts connecting with nutritive or pericarpic gametophytic cells and coming to line a cavity formed by breakdown of the auxiliary cell, with inwardly radiating filaments bearing terminal or short rows of carposporangia; spermatangia in sunken ampulliform clusters

ACROTYLACEAE

13. Thallus regularly pinnately branched, in a few genera pulvinate and parasitic; medulla entirely or largely of ovoid cells, with no or few slender filaments (apart from filaments surrounding the axial filament in Phacelocarpus)

14

13. Thallus irregularly radially or complanately branched; medulla entirely or largely of slender filaments, or with numerous filaments surrounding larger cells

17

14. Thallus distichously branched, with regularly arranged lateral pinnules or branchlets; auxiliary cells in special short shoots in axils of lateral ramuli

15

14. Thallus complanately but not regularly distichously branched, or terete and radially branched; auxiliary cells usually normal cortical cells of the vegetative thal lus

16

15. Thallus branches with alternating series of 2,3 or 4–5 laterals, tetrasporangia zonate in axillary stichidia

PLOCAMIACEAE

15. Thallus branches pinnate with short, regularly arranged, spinous ramuli; tetrasporangia zonate, borne within channels in axillary or marginal ovoid receptacles

PHACELOCARPACEAE

16. Thallus usually complanately branched, branches slightly compressed to flat, cortical cells usually forming rosettes in surface view; carposporangia in chains on more or less erect and tufted gonimoblast filaments; tetrasporangia scattered

CYSTOCLONIACEAE

16. Thallus radially branched, branches terete to slightly compressed, outer cortical cells uniform; carposporangia single and terminal on small cells in scattered clusters throughout the reticulate gonimoblast; tetrasporangia usually in nemathecia around the base of short lateral branches

HYPNEACEAE

17. Thallus with surface tufts of uniseriate filaments bearing spermatangia or cruciately divided tetrasporangia; medulla densely filamentous, cortex pseudoparenchymatous

NIZYMENIACEAE

17. Thallus bearing spermatangia and zonately divided tetrasporangia on or in the cortex

18

18. Carpogonial branches directed inwards, with reflexed trichogynes (except Melanema in the Areschougiaceae)

19

18. Carpogonial branches directed outwards with relatively straight trichogynes

20

19. Non-procarpic (procarpic in Melanema), with connecting filaments between (often distant) carpogonia and auxiliary cells; carposporophyte with a large central fusion cell or a placenta of intermixed gametophytic and carposporophytic cells, with outwardly radiating gonimoblasts bearing single rows or clusters of carposporangia; spermatangia clustered on surface cortical cells

ARESCHOUGIACEAE

19. Procarpic; gonimoblasts connecting with nutritive or pericarpic gametophytic cells and coming to line a cavity formed by breakdown of the auxiliary cells, with inwardly radiating filaments bearing terminal or short rows of carposporangia; spermatangia in sunken ampulliform clusters

ACROTYLACEAE

20. Medulla of lax, separated filaments

CAULACANTHACEAE

20. Medulla with a central core of slender filaments surrounded by large ovoid cells (and filaments), then a small-celled cortex

MYCHODEACEAE


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