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Holotrichia comosa (Harvey) Schmitz in Schmitz & Falkenberg 1897: 450, fig. 252B, C.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Lophothalieae

Selected citations: De Toni 1903: 1145. Falkenberg 1901: 566, pl. 24 figs 12, 13. Huisman & Walker 1990: 435. Kylin 1956: 516, fig. 408C, D. Lucas 1909: 47. May 1965: 378. Silva et al. 1996: 500.


Alsidium comosum Harvey 1863, pl. 270, synop.: xviii. J. Agardh 1896: 113. Schmitz 1893: 230 (in part). Sonder 1880: 34. Tisdall 1898: 513. Wilson 1892: 168.

Maschalostroma fastigiata sensu Guiler 1952: 104. Lucas 1909: 39. Lucas & Perrin 1947: 253, fig. 112.

Thallus (Fig. 111A) medium to dark red-brown, 10–35 cm high, with robust, cartilaginous, branched lower axes (probably perennial) 2–10 mm in diameter, bearing plumose upper branches 5–20 cm long, branched for 3–4 orders and profusely covered with rhodoplastic trichoblasts and adventitious filaments; axes corticated, well defined, 0.5–1.5 mm in diameter, upper branches radial, tapering to 20–60 µm in diameter shortly below apices. Holdfasts (Fig. 111A) relatively massive, perennial, coarsely fibrous, 1–3 cm across. Structure monopodial (Fig. 111B) with trichoblasts arising from third or fourth axial cells, maturing rapidly, and pericentral cells (usually 7, Fig. 111C) cut off from segments 6–10, with some pericentral cells dividing transversely into 2, the trichoblast attached to the upper cell. Trichoblasts (Fig. 111B) simple, arising spirally 1/4, 0.2–1 mm long when mature, 16–24 1 µm in diameter, tapering gently, basal cells L/D 0.5–1, mid cells L/D (2–) 4–8 (–10). "Gland" cells part way along (Fig. 111H) some trichoblasts (and probably adventitious filaments), usually single, formed following division of a cell to give an isodiametric, angular, cell 8–30 µm in diameter, with a small cell above; one of these 2 cells usually darkly staining. Adventitious monosiphonous filaments frequent, similar to trichoblasts (or slightly slenderer), arising from pericentral cells and later from cortical cells. Cortication (Fig. 111D) commencing well below apices, becoming thick, with cells with darkly staining contents ("gland" cells) rare to abundant (Fig. 111E), on the surface or within the cortex, outer cortical cells 5–10 µm across and L/D 1–2 (–4), angular and in rows. Pericentral cells soon lost (Fig. 111D) in transverse section among inner cortex cells of similar size and abundant rhizoids. Laterals arising on basal cell of trichoblasts. Cells probably uninucleate; rhodoplasts discoid, becoming chained.

Reproduction: Gametophytes dioecious. Procarps on basal (or near) cell of trichoblasts. Carposporophytes with a small basal fusion cell and branched gonimoblast filaments with clavate terminal carposporangia 35–55 µm in diameter, replaced from below. Cystocarps (Fig. 111F) ovoid, 700–1500 µm in diameter, sessile, with no neck; pericarp ostiolate, 3–4 cells thick, with 10–25 erect filaments cutting off outer pericentral cells and an outer layer of small cortical cells. Spermatangial organs (Fig. 111G) on mid cells of trichoblasts with sterile basal and apical filaments, 200–300 µm long and 60–80 µm in diameter.

Tetrasporangia in lesser branches (Fig. 111H), fertile parts 1–2 mm long and 120–180 µm in diameter, with trichoblasts and adventitious filaments from each segment, one tetrasporangium per segment, spirally arranged, (35–) 50–130 µm in diameter, each with 3 cover cells.

Type from "The Vasse" (near Busselton), W. Aust., holotype in Herb. Harvey, TCD.

Selected specimens: Cavenagh Reef, Cervantes, W. Aust., 5 m deep (Edgar, 2.xi.1999; AD, A68384). Point Clune, Rottnest I., W. Aust., 12 m deep (Kraft & Ricker, 5.xii.1980; MELU, K7203a). Between Backstairs Passage and Troubridge I., S. Aust. (AD, A16139). Tiparra Reef, S. Aust., 5 m deep (Shepherd, 30.ix.1970; AD, A37282), 11 m deep (Shepherd, 31.x.1970; AD, A37635-"Marine Algae of southern Australia" No. 130) and 10–12 m deep (Shepherd, 16.iii.1985; AD, A56437). Off Outer Harbor, S. Aust., 17 m deep (Shepherd, 26.vii.1969; AD, A35110). Glenelg, S. Aust., on tyre reef, 18 m deep (Reimers, 9.x.1986; AD, A57265). NE of Ballast Head, Kangaroo I., S. Aust., 12 m deep (Hone, 13.ii.1997; AD, A66939).

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

Distribution: Rottnest I., W. Aust., to Glenelg, S. Australia.

Taxonomic notes: Holotrichia comosa occurs in relatively deep water in areas of moderate water movement.


AGARDH, J.G. (1896). Analecta Algologica. Cont. III. Acta Univ. lund. 32, 1–140, Plate 1.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3. pp. 775–1521 + 1523–1525. (Padua.)

FALKENBERG, P. (1901). Die Rhodomelaceen des Golfes von Neapel und der angrenzenden Meeres-abschnitte. Fauna und Flora des Golfes von Neapel. Monogr. 26. (Friedländer: Berlin.)

GUILER, E.R. (1952). The marine algae of Tasmania. Checklist with localities. Pap. Proc. R. Soc. Tasmania 86, 71–106.

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

HUISMAN, J.M. & WALKER, D.I. (1990). A catalogue of the marine plants of Rottnest Island, Western Australia, with notes on their distribution and biogeography. Kingia 1, 349–459.

KYLIN, H. (1956). Die Gattungen der Rhodophyceen. (Gleerups: Lund.)

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

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

MAY, V. (1965). A census and key to the species of Rhodophyceae (red algae) recorded from Australia. Contr. N.S. W. Natl Herb. 3, 349–429.

SCHMITZ, F. & FALKENBERG, P. (1897). Rhodomelaceae. In Engler, A. & Prantl, K., Die natürlichen Pflanzenfamilien. T.1. Abt. 2, pp. 421–480. (Englemann: Leipzig.)

SCHMITZ, F. (1893). Die gattung Lophothalia, J. Ag. Ber. Deutsch. Bot. Ges. 11, 212–232.

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

SONDER, O.W. (1880). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

TISDALL, H.T. (1898). The algae of Victoria. Rep. 7th Meet. Aust. Ass. Adv. Sci., Sydney, 1898, pp. 493–516.

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

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

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 2003: FIG. 111.

Figure 111 image

Figure 111   enlarge

Fig. 111. Holotrichia comosa (A, F, AD, A37635; B–D, AD, A57265; E, H, AD, A56437; G, AD, A66939). A. Habit. B. Branch apex and trichoblasts. C. Transverse section of young branch with adventitious trichoblasts. D. Transverse section of older branch. E. Transverse section of old branch with darkly stained ("gland") cell contents. F. Cystocarps. G. Spermatangial organs. H. Branch with tetrasporangia, trichoblasts with "gland" cells.

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