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Hydrolithon cymodoceae (Foslie) Penrose 1992a: 89, figs 1–30.

Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Mastophoroideae


Melobesia cymodoceae Foslie 1901: 23. Wilks & Woelkerling 1991: 528.

Heteroderma cymodoceae (Foslie) Adey 1970: 16.

Fosliella cymodoceae (Foslie) Jones & Woelkerling 1984: 184, figs 3,6–13.

Thallus encrusting, up to 1 mm thick, epiphytic and affixed by cell adhesion. Structure pseudoparenchymatous; organisation dorsiventral; construction dimerous or monomerous, dimerous portions consisting of a single ventral layer of branched filaments composed of non-palisade cells, and unicellular or multicellular simple or branched filaments that arise more or less perpendicularly from cells of ventral layer filaments, monomerous portions consisting of a single system of branched filaments that collectively contribute to a ventrally or centrally situated core, and a peripheral region where portions of core filaments or their derivatives curve outwards towards the thallus surface, each filament composed of cells 5–20 µm in diameter and 5–30 µm long; epithallial cells terminating filaments at the thallus surface, distal walls rounded or flattened but not flared; cells of adjacent filaments joined by cell-fusions, secondary pit-connections absent; trichocytes occurring commonly in horizontal rows and singly at thallus surface, not becoming buried within thallus.

Reproduction: Vegetative reproduction unknown. Gametangia, carposporangia,
tetrasporangia and bisporangia produced in uniporate conceptacles.

Gametangial plants monoecious; carpogonia and spermatangia produced in separate conceptacles. Carpogonia terminating 3-celled filaments arising from the female conceptacle chamber floor. Mature female-carposporangial conceptacle roofs protruding above or flush with surrounding thallus surface, composed of 2–4 cells above the chamber, pores orientated obliquely to surrounding thallus surface; conceptacle chambers 90–150 µm in diameter and 65–150 µm high. Carposporophytes developing within older female conceptacles after karyogamy, when mature composed of a large central fusion cell and gonimoblast filaments bearing terminal carposporangia. Spermatangial filaments unbranched, arising from the floor of male conceptacle chambers, mature male conceptacle roofs protruding above or flush with surrounding thallus surface, conceptacle chambers 90–105 µm in diameter and 50–85 µm high.

Tetrasporangial and bisporangial conceptacle roofs protruding above or flush with surrounding thallus surface, 2–4 cells thick above the chamber, pore canals lined with non-protruding cells, conceptacle chambers 30–260 µm in diameter and 80–160 µm high; a single sporangium usually formed in the conceptacle chamber, sometimes 2 sporangia formed across the conceptacle chamber floor, each mature sporangium 45–135 µm in diameter and 80–185 µm long, usually zonately divided, sometimes irregularly divided.

Type from Port Phillip Bay, Vic. (F. v. Mueller, 1862); lectotype in TRH (unnumbered), designated by Adey & Lebednik (1967: 32); illustrated by Penrose (1992a, figs 1,2).

Selected specimens: Observatory Point, Esperance, W. Aust., 2–3 m deep (Woelkerling, Platt & Jones, 5.ii.1984; LTB, 14152). Dempster Point, Israelite Bay, W. Aust., 0–2 m deep (Woelkerling, Platt & Jones, 8.ii.1984; LTB 14254). 7 km E of Twilight Cove, Eyre, W. Aust., 0–3 m deep (Woelkerling, Platt & Jones, 2.ii. 1984; LTB, 14067). Point Fowler (E shore), S. Aust., 2–3 m deep (Woelkerling, Platt & Jones, 14.ii.1984; LTB, 14388). Point Sinclair, S. Aust., 0–2 m deep (Woelkerling, Platt & Jones, 15.ii.1984; LTB, 14489). Vivonne Bay, Kangaroo I., S. Aust., upper sublittoral (Woelkerling, 23.ii.1979; LTB, 11646, 11648). Apollo Bay, Vic., upper subtidal (Bramwell, 30.xii.1981; LTB, 14658). Torquay, Vic. (Bramwell, 14.i.1982; LTB, 15266). Flinders, Vic., intertidal pools (Woelkerling, 19.xi.1983; LTB, 13893). Rye, Vic., intertidal pools (Kay, 10.viii.1978; LTB, 11104). Kitty Miller Bay, Phillip I., Vic., upper subtidal (Woelkerling, Campbell & Penrose, 2.xii.1985; LTB, 15231). Walkerville North, Vic. (Woelkerling, 26.xi.1976; LTB, 11195).

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

Distribution: Shark Bay, W. Aust. (Harlin et al. 1985; Penrose 1992a) to Walkerville, Vic.

Taxonomic notes: H. cymodoceae occurs commonly in southern Australia and is found predominantly growing on the leaves and stems of the seagrass, Amphibolis antarctica (Penrose 1992a). The species is readily distinguished from others by the presence of a single tetrasporangium within the conceptacle chamber. Additional information on the species has been provided by Penrose (1990, 1992a).


ADEY, W.H. & LEBEDNIK, P.A. (1967). Catalog of the Foslie Herbarium. (Det Kongelige Norske Videnskabers Selskab Museet: Trondheim, Norway.)

ADEY, W.H. (1970). A revision of the Foslie crustose coralline herbarium. K. norske Vidensk. Selsk. Skr. 1970 (1), 1–46.

HARLIN, M.M., WOELKERLING, Wm.J. & WALKER, D.I. (1985). Effects of a hypersalinity gradient on epiphytic Corallinaceae (Rhodophyta) in Shark Bay, Western Australia. Phycologia 24, 389–402.

JONES, P.L. & WOELKERLING, Wm.J. (1984). An analysis of trichocyte and spore germination attributes as taxonomic characters in the Pneophyllum&ndsah;Fosliella complex (Corallinaceae, Rhodophyta). Phycologia 23, 183–194.

PENROSE, D.L. (1990). Taxonomic studies on Spongites and Neogoniolithon (Corallinaceae, Rhodophyta) in southern Australia. Unpublished PhD Thesis, La Trobe University, Bundoora, Victoria, Australia.

PENROSE, D. (1992a). Hydrolithon cymodoceae (Corallinaceae, Rhodophyta) in southern Australia and its relationships to Fosliella. Phycologia 31, 89–100.

WILKS, K.M. & WOELKERLING, W.J. (1991). Southern Australian species of Melobesia (Corallinaceae, Rhodophyta). Phycologia 30, 507–533.

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

Author: D.L. Penrose

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. 116.

Figure 116 image

Figure 116   enlarge

Fig. 116. Hydrolithon cymodoceae (A, LTB, 14489; 13, LTB, 14254; C, LTB, 14388; D, LTB, 13893). A. Plants epiphytic on leaves and stems of the seagrass Amphibolis antarctica. B. Section of tetrasporangial conceptacle with a single sporangium lying horizontally in the chamber and distinctive cells lining the pore canal. C. Section of spermatangial conceptacle with initials formed across the chamber floor bearing spermatangia. D. Section of carposporangial conceptacle with a more or less ovoid fusion cell, a large carposporangium and a pore canal that is orientated obliquely to the thallus surface.

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