Electronic Flora of South Australia Species Fact Sheet

Hypnea filiformis (Harvey) Womersley, comb. nov.

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Hypneaceae

Synonym

Heringia filiformis Harvey 1855a: 549. J. Agardh 1876: 438; 1894: 137. De Toni 1900: 403.

Thallus (Fig. 153A) medium to dark red, 3–14 cm high, with percurrent main branches bearing radially irregular laterals at intervals of 2–12 mm below, less near the apices, but without the numerous short lateral branchlets typical of most species of Hypnea; branches terete, filiform, tapering apically, lower branches 400–700 (–900) µm in diameter, decreasing gradually to 250–400 µm in diameter shortly below the apices; occasional branches hamate. Holdfast fibrous to stoloniferous, slender, with small hapteroid discs attaching to stones or other algae; epilithic or epiphytic. Structure uniaxial, with a protruding apical cell, axial filament distinct throughout, becoming 40–100 (–140) µm in diameter with cells L/D 4–8, surrounded by a medulla 2–3 cells broad, cells large, ovoid, thick-walled, 50–90 (–130) µm in diameter (Fig. 153B) with numerous secondary pit-connections, and a small-celled cortex (1–) 2 cells broad, outer cells 5–12 (–18) µm in diameter and L/D 1–2. Rhodoplasts discoid and numerous in outer cells, becoming ribbon shaped in medullary cells.

Reproduction: Sexual thalli dioecious. Carpogonial branches and early post-fertilization stages not observed. Carposporophyte (Fig. 153C) with a lax reticulum of elongate cells with shorter cells producing clusters of small cells which cut off single, subspherical to ovoid carposporangia 18–28 µm in diameter. Cystocarps globular, protuberant, 0.75–1.25 mm in diameter, sessile and not basally constricted, with a pericarp 4–8 cells thick, non-ostiolate.

Type from Garden I., W. Aust. (Harvey, Tray. set 182); not located in TCD. [Harvey, Alg. Aust. Exsicc. 312a, from the "Swan R.", is in TCD].

Selected specimens: Port Denison, W. Aust., drift (Kraft 4003, 14.xii.1971; AD, A41722), Venus Bay, S. Aust., reef pools (Womersley, 17.i.1951; AD, A15155). Elliston, S. Aust., 20 m deep outside bar (Shepherd, 14.v.1971; AD, A38704). Sleaford Bay, S. Aust., rear reef pools, shaded (Womersley, 16.ii.1959; AD, A22510). Tapley Shoal, S. Aust., 13 m deep on E side (Shepherd, 5.ii.1969; AD, A33755). O'Sullivans Beach, S. Aust., 7 m deep (R. Lewis, 23.iii.1972; AD, A41588). Pennington Bay, Kangaroo I., S. Aust., rear reef pools (Womersley, 22.viii.1954; AD, A19769 and Prud'homme van Reine, 26.ix.1988; AD, A59120). Robe, S. Aust., shaded rear reef pool (Womersley, 7.xii.1991; AD, A61512). Nora Creina, S. Aust., upper sublittoral in bay (Goff & Womersley, 12.ix.1983; AD, A54290).


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

Distribution: Port Denison, W. Aust., to Nora Creina, S. Aust.

Taxonomic notes: Spermatangia (Fig. 154A) scattered, cut off via initials from outer cortical cells, ovoid, 3–4 µm in diameter.

Tetrasporangia (Fig. 154B) scattered in the cortex of lateral branches, basally pit-connected to inner cortical cells, ovoid, 35–55 µm long and 18–35 µm in diameter, zonately divided by successive cleavages.

H. filiformis has a cystocarp typical of Hypnea, with clusters of single, terminal, carposporangia within a non-ostiolate pericarp. It differs from other species in lacking the numerous short, often spinous, branchlets covering the main branches, and in the tetrasporangia lying in the cortex of the branches rather than in distinct basal nemathecia on the branchlets. In some plants the tetrasporangia appear to be liberated as bisporangia, though some cleavages into four spores are usually visible.

References:

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. (1894). Analecta Algologica. Cont. II. Acta Univ. lund. 30, 1–98, Plate 1.

DE TONI, G.B. (1900). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 2, pp. 387–776. (Padua.)

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

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.


Illustrations in Womersley Part IIIA, 1994: FIGS 153 A–C, 154A, B.

Figure 153 image

Figure 153   enlarge

Fig. 153. A–C. Hypnea filiformis (A, AD, A54290; B, AD, A38704; C, AD, A41588). A. Habit. B. Transverse section of older branch. C. Section of cystocarp with clusters of carposporangia. D–G. Hypnea ramentacea (D, AD, A54993; E, AD, A43719; F, G, AD, A42362). D. Habit. E. Section of cystocarp with clusters of carposporangia. F. Laterals with spermatangial sori. G. Longitudinal section of spermatangial branchlet.

Figure 154 image

Figure 154   enlarge

Fig. 154. A, B. Hypnea filiformis (A, AD, A19769; B, AD, A61512). A. Section of cortex with spermatangia. B. Transverse section of cortex with tetrasporangia. C. Hypnea ramentacea (AD, A42362). Section of cortex with spermatangia. D, E. Hypnea charoides (D, AD, A61582; E, AD, A60042). D. Section of cortex with spermatangia. E. Section of cortex with tetrasporangia. F. Hypnea valentiae (AD, A48965). Section of cortex with tetrasporangia. G–I. Catenella nipae (G, AD, A60381; H–I, AD, A26432). G. Habit of a tetrasporangial plant. H. Longitudinal section of apical segment with several carpogonial branches and a fusion cell producing gonimoblast initials. I. Longitudinal section of cortex with tetrasporangia. [H, I after Min-Thein & Womersley 1976.]


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