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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Mastophoroideae
Synonym
Goniolithon Foslie (1900b) subg. Hydrolithon Foslie 1905: 7.
Thallus encrusting, warty or lumpy, epilithic, epiphytic or epizoic and affixed by cell adhesion, or unattached and free-living as rhodoliths; genicula absent. 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; cells of adjacent filaments joined by cell-fusions, secondary pit-connections absent; epithallial cells terminating filaments at the thallus surface, distal walls rounded or flattened but not flared; trichocytes present or absent, if present appearing, in section, arranged in horizontal fields, horizontal rows, vertical rows, or occurring singly at the thallus surface, sometimes becoming buried within the thallus.
Reproduction: Vegetative reproduction by thallus fragmentation. Gametangia, carposporangia, tetrasporangia and bisporangia borne in uniporate conceptacles; gametangia and carposporangia usually formed on separate plants from tetrasporangia and bisporangia.
Gametangial plants monoecious or dioecious; carpogonia and spermatangia produced in separate conceptacles. Carpogonia terminating 3-celled filaments arising from the female conceptacle chamber floor. Carposporophytes developing within female conceptacles after karyogamy, composed of a large central fusion cell and gonimoblast filaments bearing terminal carposporangia. Spermatangial filaments unbranched, formed on the chamber floor.
Tetrasporangia and bisporangia formed across the chamber floor or peripheral to a central columella, conceptacle roofs formed by filaments surrounding and interspersed amongst sporangial initials, each mature sporangium lacking an apical plug, usually regularly zonately divided.
Type species: Hydrolithon reinboldii (W.-van Bosse & Foslie)Foslie 1909: 55.
Taxonomic notes: Hydrolithon includes six species on southern Australian coasts. The following account is based mainly on data in Penrose (1990, 1992a) and Penrose & Chamberlain (1993).
References:
FOSLIE, M. (1909). Algologiske notiser. VI. K. norske Vidensk. Selsk. Skr. 1909(2), 1–63.
PENROSE, D. & CHAMBERLAIN, Y.M. (1993). Hydrolithon farinosum (Lamouroux) comb. nov.: implications for generic concepts in the Mastophoroideae (Corallinaceae, Rhodophyta). Phycologia 32, 295–303.
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.
The Marine Benthic Flora of Southern Australia Part IIIB complete list of references.
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.
KEY TO SPECIES OF HYDROLITHON
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1. Tetrasporangial conceptacles usually containing a single sporangium lying horizontally within the chamber (occasionally containing two upright sporangia); carposporangial conceptacles containing a single carposporangium in the chamber, pore canals formed obliquely to the surrounding thallus surface | H. cymodoceae |
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1. Tetrasporangial conceptacles containing two or more upright sporangia within the chamber, carposporangial conceptacles containing more than one carposporangium peripherally in the chamber, pore canals formed perpendicularly to the surrounding thallus surface | 2 |
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2. Thallus commonly composed of a number of applanate branches that overgrow one another and are attached to one another by cell adhesion and rhizoids | H. improcerum |
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2. Thallus rarely with applanate branches that overgrow one another and are attached to one another by cell adhesion and rhizoids | 3 |
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3. Thallus epiphytic, | H. farinosum |
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3. Thallus epilithic or epizoic, >10 cells high when reproductively mature | 4 |
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4. Thallus commonly with horizontal rows of trichocytes occurring at the surface and buried within the thallus | H. onkodes |
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4. Thallus occasionally with horizontal rows of trichocytes at the surface, lacking such rows buried within the thallus | 5 |
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5. Tetrasporangial conceptacles usually containing sporangia across the chamber floor and lacking a central columella, chambers usually >150 µm in diameter | H. munitum |
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5. Tetrasporangial conceptacles usually containing sporangia peripherally in the chamber and lacking a central columella, chambers usually <110 pm in diameter | H. rupestris |
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