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Lomentaria pyramidalis Kraft & Womersley, nov. sp.

Phylum Rhodophyta – Class Florideophyceae – Order Rhodymeniales – Family Lomentariaceae

Thallus (Fig. 58A) medium to dark red, mucilaginous, (2–) 5–20 (–45) cm high, more or less pinnately branched for 3–4 orders but not strictly distichous, with scattered branchlets from the face of parent branches, with percurrent axes and main branches. Larger and mid branches compressed, basally constricted and tapering to a rounded apex, main branches (2–) 3–4 (–5) mm broad and 300–500 µm thick, lesser branches 1–2 mm broad, branchlets subterete and 300–600 µm broad. Holdfast discoid, 1–3 mm across, bearing 2–5 fronds; epiphytic on Posidonia or Amphibolis (or Acrocarpia) or possibly epilithic. Structure multiaxial, with a cluster of apical cells producing filaments which interconnect to form a lax medullary network on the inside of the cortex (Fig. 58B), filaments 4–6 µm in diameter and producing ovoid secretory cells 6–8 µm in diameter; older segments with denser medullary filaments, filling the segment near the thallus base. Cortex 2–3 cells thick above, 3–5 cells thick below, the inner cortex with an outer layer of ovoid to isodiametric cells 12–30 µm across, a mid layer of more elongate cells, and an inner layer of elongate cells connected to the medullary filaments, with a sparse outer cortex of small ovoid cells, 5–10 µm in diameter, cut off around the larger cells, dividing to form very slight rosettes on older branches. Hairs common. Branch constrictions (Fig. 58C) solid, pseudoparenchymatous. Rhodoplasts discoid, in chains in most cells.

Reproduction: Gametangial thalli dioecious. Carpogonial and auxiliary cell branches not observed. Carposporophyte (Fig. 58D) erect with a massive basal fusion cell producing slender gonimoblast filaments with all upper cells forming ovoid to clavate carposporangia 15–30 µm in diameter; basal nutritive tissue present, erect filaments disintegrating. Cystocarps scattered on lesser branches or surface of compressed branches, external, often near branch bases, globular to slightly urceolate and beaked, basally constricted, 600–900 µm in diameter, ostiolate; pericarp 35–60 µm and 4–8 cells thick, inner cells stellate. Spermatangia (Fig. 58E) cut off via initials from cells of the rosettes, ovoid, 2–3 µm in diameter.

Tetrasporangia in irregular to elongate, depressed sori (Fig. 58F) 200–500 µm across, numerous per sorus, cut off inwardly (Fig. 58G) from small cells lining the depression, subspherical, 50–75 µm in diameter, tetrahedrally divided.

Type from Port MacDonnell, S. Aust., drift (Womersley, 19.viii.1953); holotype and isotypes in AD, A18983).

Selected specimens: Point Peron, W. Aust., drift (Womersley, 18.viii.1979; AD, A51006). Marino, S. Aust., drift (Womersley, 26.x.1975; AD, A46642). Robe, S. Aust., drift on Posidonia australis (Womersley, 24.viii.1960; AD, A24438 and 15.v.1965; AD, A29273) and on jetty piles, 1–2 m deep (Womersley & R. Lewis, 14.v.1972; AD, A42199). Port MacDonnell, S. Aust., drift (Womersley, 18.ix.1993; AD, A63027, and G. & R. Kraft, K9096, 25.ix.1992; MELU and AD, A63400). Gardens Beach, Portland Bay, Vic., drift (Beauglehole, 11.viii.1951; AD, A21654). Queenscliff, Vic., 4–5 m deep near jetty, on Amphibolis (Kraft & Saunders, 9.ix.1993; MELU, K9591). Flinders, Vic., drift (Womersley, 25.x.1986; AD, A57839 and Kraft & Hommersand, 4.viii.1995; MELU).

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

Distribution: Point Peron, W. Aust., to Flinders, Vic.

Taxonomic notes: L. pyramidalis is a distinctive, large, species of pyramidal form, with a single discoid holdfast and most commonly epiphytic on Posidonia on the SE coast of South Australia.

References: The Marine Benthic Flora of Southern Australia Part IIIB

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 1996: FIG. 58.

Figure 58 image

Figure 58   enlarge

Fig. 58. Lomentaria pyramidalis (A–C, E–G, AD, A18983; D, AD, A29273). A. Habit. B. Transverse section of compressed branch. C. Longitudinal section with a constriction. D. Section of cystocarp showing basal fusion cell and carposporangia. E. Surface view of spermatangial sorus. F. Surface view of tetrasporangial sori. G. Transverse section of branch with tetrasporangial sori.

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