Electronic Flora of South Australia Species Fact Sheet

Heterosiphonia lawrenciana (Harvey) Parsons 1975: 618, 625, fig. 43.

Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae

Selected citations: Silva et al. 1996: 442.

Synonyms

Polysiphonia lawrenciana Harvey 1844: 438. Kützing 1849b: 832.

Dasya lawrenciana (Harvey) Harvey 1847: 60, p1. 18; 1859: 302. Kützing 1864: 25, pl. 70. Sonder 1853: 702.

Dasya gunniana var. lawrenciana (Harvey) Harvey 1863, synop.: xxii. Sonder 1881: 35. Wilson 1892: 165.

Dasya gunniana f. lawrenciana (Harvey)J. Agardh 1863: 1201.

Thallus (Fig. 230A) medium to dark red-brown, erect with one to a few main axes, 10–40 cm high, axes becoming 2–3 mm in diameter for 5–30 cm (probably perennial) and denuded apart from re-growth, lesser branches alternately distichous, mostly 2–5 mm apart, terminating in flabellate tufts of rhodoplastic filaments, with the polysiphonous segments soon becoming corticated and obscured. Holdfast discoid to conical, 2–10 mm across; epilithic. Structure. Apices of axes sympodial and distichous, developing 8–9 (–10) pericentral cells (Fig. 230B). Pseudolaterals (2–) 3–5 segments apart, each with 2–4 lower subdichotomies 2–4 cells apart, the lower several segments becoming polysiphonous and with upper monosiphonous filaments (Fig. 230D), lower cells 35–65 µm in diameter and L/D 0.5–1.3, tapering gradually to upper cells 15–30 in diameter and L/D 2–3.5. Cortication commences by cells cut off the pericentral cells and soon becomes complete, obscuring the pericentral cells; in older axes, a cortex many cells thick develops, with a conspicuous central axial cell but the pericentral cells obscured (Fig. 230C). Rhodoplasts discoid.

Reproduction: Gametophytes dioecious or monoecious. Procarps on lower segments of pseudolaterals, becoming polysiphonous, with a pericarp developed pre-fertilization (Fig. 230D), adjacent pseudolaterals usually slenderer than normal pseudolaterals. Cystocarps (Fig. 230E) large, ovoid, 1–1.5 mm in diameter, with little or no neck, on polysiphonous corticated branches; gonimoblast much branched, with a basal fusion cell and ovoid carposporangia 40–50 µm in diameter; pericarp with a cortex 2–3 cells thick. Spermatangial branches (Fig. 230F)as terminal branches of pseudolaterals, lanceoid to cylindrical with short monosiphonous pedicels and terminal filaments, 90–400 µm long and 35–45 µm in diameter.

Tetrasporangial stichidia (Fig. 230G) as ultimate branches of pseudolaterals, with a polysiphonous (becoming corticated) base and blunt apex, cylindrical, 500–1000 long and 200–300 µm in diameter, with 6 pericentral cells and tetrasporangia per whorl with 2 cover cells divided horizontally and somewhat irregular; sporangia 60–90 µm in diameter.

Type from Georgetown, Tas.; lectotype Gunn 1268, in BM.

Selected specimens: Cottesloe, W. Aust. (Baird, July 1935; UWA, A888). Garden I., W. Aust. (Smith, Nov. 1948; UWA, A374, A889). Eyre, W. Aust., drift (Parsons, 22.xi.1968; AD, A34409). Eucla, W. Aust., drift (Parsons, 5.xi.1968; AD, A33372). N Spencer Gulf, S. Aust., 10 m deep (Shepherd, 6.ix.1973; AD, A44335). Off Troubridge Light (Edithburg), S. Aust., 17 m deep (Shepherd, 4.ii.1969; AD, A37268). Port Turton, S. Aust., 8–10 m deep (Kald, 5.ix.1970; AD, A37261). Henley Beach, S. Aust. (AD, A1462). Aldinga, S. Aust., shaded pool (Bailey, 21.xi.1965; AD, A29700). Granite I., Victor Harbor, S. Aust., 7–10 m deep E of causeway (Edyvane, 8.viii.1982; AD, A53197). Port Phillip Heads (Wilson, 4.i.1889; MEL, 1006029). Low Head, Tas. (Perrin, Feb. 1940; HO, 47910).

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

Distribution: Cottesloe, W. Aust., to Port Phillip Heads, Vic., and N Tasmania.

Taxonomic notes: H. lawrenciana is closely related to H. gunniana, especially in reproductive organs, as was discussed by Parsons (1975, pp. 618, 625). H. lawrenciana is characterised by cortication of the polysiphonous segments starting early, so that only few polysiphonous segments are visible near the apices; this early cortication also occurs on the stalks of the stichidia. The basal parts of the axes become heavily corticated, and transverse sections show a large central cell but the pericentral cells are inconspicuous amongst the similar-sized rhizoidal corticating cells. This basal thickened part is probably perennial, many specimens showing slender regrowth from its upper parts. In contrast to the above, H. gunniana has polysiphonous segments visible well below the upper parts, cortication commencing much later, and in old corticated axes the pericentral cells remain conspicuous around the axial cell and are of similar size.

Detailed studies are still needed of these differences, especially to follow seasonal development.

References:

AGARDH, J.G. (1863). Species Genera et Ordines Algarum. Vol. 2, Part 3, pp. 787–1291. (Gleerup: Lund.)

HARVEY, W.H. (1844). Algae of Tasmania. Lond. J. Bot. 3, 428–454.

HARVEY, W.H. (1847). Nereis Australis, pp. 1–64, Plates 1–25. (Reeve: London.)

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

KÜTZING, F.T. (1864). Tabulae Phycologicae. Vol. 14. (Nordhausen.)

PARSONS, M.J. (1975). Morphology and taxonomy of the Dasyaceae and Lophothalieae (Rhodomelaceae) of the Rhodophyta. Aust. J. Bot. 23(4), 549–713.

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (University of California Press: Berkeley, Los Angeles & London.)

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

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

WILSON, J.B. (1892). Catalogue of algae collected at or near Port Phillip Heads and Western Port. Proc. R. Soc. Vict. 4, 157–190.

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

Author: M.J. Parsons and H.B.S. Womersley

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia

Illustration in Womersley Part IIIA, 1998: FIG. 230.

Figure 230   enlarge

Fig. 230. Heterosiphonia lawrenciana (A–D, AD, A33372; E–G, AD, A34409). A. Habit. B. Transverse section of young axis. C. Transverse section of old basal axis. D. Branch with pseudolaterals and young cystocarps. E. Mature cystocarp. F. Spermatangial branches. G. Stichidia.

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