Electronic Flora of South Australia Species Fact Sheet

Mychodea gracilaria (Sonder) Kraft 1978: 528, figs 5,6,32.

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Mychodeaceae

Synonyms

Acanthococcus gracilaria Sonder 1853: 683.

Mychodea carnosa sensu Harvey 1855a: 555; 1860b: p1. 142 figs 2,3.

Mychodea membranacea sensu Harvey 1860a: 323; 1863, synop.: xlii. J. Agardh 1872: 34; 1876: 571; 1897: 50. Kützing 1866: 27, p1. 77a, b. Lucas & Perrin 1947: 156.

Thallus (Fig. 158D) dark red to yellow-brown, 10–25 cm high, irregularly radially branched with spreading subterete laterals (Fig. 160A) and ramuli tapering gradually to acute apices, not constricted basally. Holdfast crustose, thin, 1–3 mm across, bearing one to several axes; epiphytic on Amphibolis and occasionally on Posidonia or stalked tunicates. Structure (Fig. 160B, C) uniaxial, developing similarly to M. carnosa; cortex with outer cells evenly distributed, not forming rosettes, ovoid, 3–6 µm in diameter. Rhodoplasts discoid to elongate, ribbon like in inner cells.

Reproduction: Sexual thalli monoecious; procarpic; polycarpogonial. Carpogonial branches (Fig. 160D) 3-celled, 2–6 borne on inner cortical (supporting) cells which become auxiliary cells, producing gonimoblast initials mainly inwardly, forming chains of irregularly maturing ovoid carposporangia 14–22 µm in diameter, with slight filamentous enveloping tissue (Fig. 158E); ostiole absent. Spermatangia (Fig. 160E) in scattered clusters on basal cells in the outer cortex, with 4–6 initials each cutting off two spermatangia 1–2 µm in diameter.

Tetrasporangia (Fig. 160F) scattered, intercalary, transformed from mid cortical cells and each bearing two groups of outer cortical cells, ovoid, 47–55 µm long and 30–35 µm in diameter, zonately divided.

Type from Lefevre Pen., S. Aust. (Mueller, 16.xii.1847); lectotype in MEL, 1007309; isolectotypes also in MEL.

Selected specimens: Thompsons Bay, Rottnest I., W. Aust., drift on Amphibolis (Kraft, 17.viii.1966; AD, A44686). Albany, W. Aust., drift (Kraft, 11.xii.1971; AD, A44687). Tiparra Reef, S. Aust., 11 m deep on Amphibolis (Shepherd, 24.ii.1971; AD, A38245). Marino, S. Aust., 3–4 m deep on Amphibolis (Kraft & Owen, 19.i.1973; A44688). Cape Jaffa, S. Aust., drift (Womersley, 10.xii.1991; AD, A61578). Sorrento, Vic., 11 m deep in bay (Womersley, 7.iv.1959; AD, A22776). Cats Bay, Phillip I., Vic. (Norris, 30.i.1963; AD, A27487). Georgetown, Tas. (Harvey, Mar. 1854; TCD, Alg. Aust. Exsicc. 4121).


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

Distribution: Rottnest I., W. Aust., to Phillip I., Vic., and northern Tasmania, usually on the seagrass Amphibolis (or Posidonia).

Taxonomic notes: Mychodea gracilaria is similar to M. carnosa but differs in having gradually tapering ramuli not constricted basally, cystocarps which become sessile on larger ramuli, and in occurring usually on robust seagrasses.

References:

AGARDH, J.G. (1872). Bidrag till Florideernes Systematik. Acta Univ. hind. 8, 1–60.

AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)

AGARDH, J.G. (1897). Analecta Algologica. Cont. IV. Acta Univ. lund. 33, 1–106, Plates 1, 2.

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Ir. Acad. 22, 525–566.

HARVEY, W.H. (1860a). Algae. In Hooker, J.D., The Botany of the Antarctic Voyage. 111. Flora Tasmaniae. Vol. II, pp. 321–343, Plates 185–196.

HARVEY, W.H. (1860b). Phycologia Australica. Vol. 3, Plates 121–180. (Reeve: London.)

HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)

KÜTZING, F.T. (1866). Tabulae Phycologicae. Vol. 16. (Nordhausen.)

KRAFT, G.T. (1978). Studies of marine algae in the lesser-known families of the Gigartinales (Rhodophyta). III. The Mychodeaceae and Mychodeophyllaceae. Aust. J. Bot. 26, 515–610.

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

SONDER, O.W. (1853). Plantae Muellerianae. Algae. Linnaea 25, 657–709.

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

Author: G.T. Kraft & 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: FIGS 158D, E, 160 A–F.

Figure 158 image

Figure 158   enlarge

Fig. 158. A–C. Mychodea carnosa (AD, A44685). A. Habit. B. Longitudinal section of branch with a mature cystocarp. C. Section of a cystocarp with enlarged auxiliary cell, gonimoblast filaments and clusters of carposporangia. D, E. Mychodea gracilaria (D, AD, A38245; E, AD, A44688). D. Habit. E. Section of cystocarp (auxiliary cell disintegrated). [A, B, D, E as in Kraft 1978.]

Figure 160 image

Figure 160   enlarge

Fig. 160. A–F. Mychodea gracilaria (AD, A44688). A. Branches with mature and young cystocarps. B. Transverse section of branch. C. Longitudinal section of branch. D. Section of cortex with two polycarpogonial supporting cells. E. Spermatangial clusters in the outer cortex. F. Section of outer cortex with an intercalary tetrasporangium. G–L. Mychodea ramulosa (AD, A44700). G. Branches with cystocarps. H. Base of plant with prostrate, attached branches and erect ones. I. Part transverse section of a branch. J. Section with polycarpogonial supporting cells. K. Section of cortex with sunken spermatangial clusters. L. Section of cortex with young, mature and germinated tetrasporangia. [A–L after Kraft 1978.]


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