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Hydrolithon onkodes (Heydrich) Penrose & Woelkerling 1992a: 81, figs 4, 5.

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

Selected citations: Verheij 1993b: 47, figs 31–35; 1994: 107, figs 31–35.


Lithothamnion onkodes Heydrich 1897c: 6, pl. 1 fig. 11a,b.

Goniolithon onkodes (Heydrich) Foslie 1898b: 8.

Lithophyllum onkodes (Heydrich) Heydrich 1901: 533.

Porolithon onkodes (Heydrich) Foslie 1909: 57.

Spongites onkodes (Heydrich) Penrose & Woelkerling 1988: 159, figs 10–14. Penrose 1990: 134, figs 44–49.

Thallus encrusting, warty or lumpy 0.1–25 mm thick, epilithic or epizoic 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 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 5–15 µm in diameter and 5–22 µm long; 1–4 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 at thallus surface, arranged in horizontal rows, horizontal fields and singly, commonly becoming buried within thallus.

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

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 flush with surrounding thallus surface, composed of 6–8 cells above the chamber, conceptacle chambers 136–191 µm in diameter and (74–) 123–150 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, pore canals formed perpendicularly to thallus surface. Spermatangial filaments unbranched, arising from the floor of male conceptacle chambers, mature male conceptacle roofs flush with surrounding thallus surface, composed of 2 or 3 cells, conceptacle chambers 69–82 µm in diameter and 55–61 µm high.

Tetrasporangial conceptacle roofs flush with surrounding thallus surface, 3–6 cells thick above the chamber, pore canals lined with non-protruding cells, conceptacle chambers 164–250 µm in diameter and 109–150 µm high; tetrasporangia usually occurring peripheral to a central columella, occasionally occurring across chamber floor, each mature sporangium 15–40 µm in diameter and 25–75 µm long, zonately divided.

Type from Tami I., north-west edge of Huon Gulf, New Guinea (Heydrich 97, Bambler, 1894); lectotype in TRH, designated by Adey et al. (1982); illustrated by Penrose & Woelkerling (1988, figs 10–14) and Penrose (1990, fig. 44A–D).

Selected specimens: Pelsart I., Houtman Abrolhos, W. Aust., outer reef (Womersley, 2.ix.1947; LTB, 13633). Port Gregory, W. Aust., reef pools (Woelkerling, 23.ii.1978; LTB, 10717, 10718, 10719). Cape Vlaming, Rottnest I., W. Aust., reef edge or pools (Woelkerling, 8.ii.1978; LTB, 10617, and 10.ii.1978, LTB, 10605, 10606, 10609, 10613, 10616). Jeannies Lookout, Rottnest I., W. Aust., 1–3 m deep (Woelkerling, 12.ii.1978; LTB, 10630, 10635). North Point Reef, Rottnest I., W. Aust., reef edge or pools (Woelkerling, 10.ii.1978; LTB, 10663, 10667). Mabel Cove, Rottnest I., W. Aust., reef top in surf (Woelkerling, 9.ii.1978; LTB, 10647). Radar Reef, Rottnest I., W. Aust., reef pools (Woelkerling, 9.ii.1978; LTB, 10656, 10657, 10660). Point Valliant, Two People Bay, W. Aust., 0.5 m deep (Woelkerling, 2.ii.1978; LTB, 10722).

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

Distribution: Known from numerous subtropical and tropical localities including, Bikini Atoll, Canary Islands, Sri Lanka, Chile, China, Clipperton Island and Costa Rica, Cuba, Ellice Islands, Hawaii, Indian Ocean, Kenya, New Guinea, North Atlantic Ocean, northern Australia, Phillipines, Red Sea, Solomon Islands, Tahiti, West Africa, subtropical and tropical W. Aust. (see Penrose 1990).

In southern Australia, known only from Point Valliant, W. Aust.

Taxonomic notes: H. onkodes is essentially a tropical species and has been collected at only one locality within the southern Australian region. Additional data on the species have been provided by Penrose (1990).


ADEY, W.H., TOWNSEND, R.A. & BOYKINS, W.T. (1982). The crustose coralline algae (Rhodophyta: Corallinaceae) of the Hawaiian Islands. Simthson. Contr. Mar. Sci. No. 15, 1–74.

FOSLIE, M. (1898b). List of species of the lithothamnia. K. norske Vidensk. Selsk. Skr. 1898(3), 1–11.

FOSLIE, M. (1909). Algologiske notiser. VI. K. norske Vidensk. Selsk. Skr. 1909(2), 1–63.

HEYDRICH, F. (1897c). Neue Kalkalgen von Deutsch-Neu-Guinea (Kaiser Wilhelms-Land). Biblthca bot. 41, 1–11, Platel.

HEYDRICH, F. (1901). Die Lithothamnien des Museum d'Histoire Naturelle in Paris. Bot. Jb. 28, 529–545, Plate 11.

PENROSE, D. & WOELKERLING, Wm.J. (1988). A taxonomic reassessment of Hydrolithon Foslie, Porolithon Foslie and Pseudolithophyllum Lemoine emend. Adey (Corallinaceae, Rhodophyta) and their relationships to Spongites Ktitzing. Phycologia 26, 159–176

PENROSE, D. & WOELKERLING, Wm. J. (1992a). A reappraisal of Hydrolithon (Corallinaceae, Rhodophyta) and its relationships to Spongites. Phycologia 31, 81–88.

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

VERHEIJ, E. (1993b). Marine Plants on the reefs of the Spermonde Archipelago, SW Sulawesi, Indonesia: Aspects of Taxonomy, Floristics, and Ecology. (Rijksherbarium/Hortus Botanicus: Leiden.)

VERHEIJ, E. (1994). Nongeniculate Corallinaceae (Corallinales, Rhodophyta) from the Spermonde Archipelago, SW Sulawesi, Indonesia. Blumea 38, 95–137.

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. 119.

Figure 119 image

Figure 119   enlarge

Fig. 119. Hydrolithon onkodes (A, LTB, 10617; B, LTB, 10722; C, D, LTB, 10647). A. Epizoic plants. B. Epilithic plants. C. Section of thallus showing a horizontal row of trichocytes. D. Section of tetrasporangial conceptacle with sporangia occurring peripherally in the chamber and a columella centrally, and large cells lining the pore canal.

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