Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Melobesioideae
Reproduction: Vegetative reproduction by thallus fragmentation. Gametangia and carposporangia borne in uniporate conceptacles; tetrasporangia and bisporangia borne in multiporate conceptacles that apparently arise from groups of subepithallial initials; gametangia and carposporangia formed on separate thalli from tetrasporangia and bisporangia.
Gametangial thalli monoecious or dioecious; carpogonia and spermatangia produced in separate conceptacles or rarely within the same conceptacle. Carpogonia terminating 2- or 3-celled filaments arising from the female conceptacle chamber floor. Mature carposporophytes apparently lacking a conspicuous central fusion cell and composed of short gonimoblast filaments bearing terminal carposporangia. Spermatangial filaments both unbranched and branched, borne on the male conceptacle chamber floor, walls and roof.
Tetrasporangia and bisporangia scattered across the conceptacle chamber floor, roofs formed by filaments interspersed amongst and peripheral to sporangial initials, each mature sporangium containing zonately arranged tetraspores or bispores and possessing an apical plug that blocks a roof pore prior to spore release.
Lectotype species: L. muelleri Lenormand ex Rosanoff 1866: 101; designated by Woelkerling (1983a: 193).
Taxonomic notes: Thallus encrusting to warty, lumpy or fruticose, epigenous and partially to completely affixed by cell adhesion or envelopment of host axes, or unattached and free-living as rhodoliths; genicula absent. Structure pseudoparenchymatous; organisation dorsiventral in crustose portions but radial in protuberant branches; construction monomerous, consisting of a single system of branched, laterally cohering, 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; cell elongation occurring mainly within actively dividing subepithallial initials that are usually as long as or longer than their immediate inward derivatives; cells of adjacent filaments joined by cell-fusions; secondary pit-connections absent; epithallial cells terminating most filaments at thallus surface, distal walls usually flattened and flared; trichocytes occasional in some species; haustoria unknown.
Over 730 species and infraspecific taxa have been ascribed to Lithothamnion (Woelkerling 1988, p. 179). The number of true species of Lithothamnion is unclear, and reliable concepts for most species scarcely exist. Wilks & Woelkerling (1995) gave a detailed account of tetrasporangial thalli of the type species, but noted that gametangia and carposporophytes are poorly known. Thus, information on gametangia and carposporophytes provided in the generic description is based mainly on species other than the type and may require revision once new data on the type species become available. Early stages of carposporophyte development and gonimoblast filament ontogeny generally are poorly known. Details relating to generic etymology, nomenclature, synonymy, infrageneric classification, etc. are provided by Woelkerling (1988, pp. 169–180). This account of southern Australian species, including the lectotype, follows Wilks & Woelkerling (1995).
Notes on other taxa reported from southern Australia
Wilks & Woelkerling (1995) provide information on 23 additional species and infraspecific taxa that at some stage were ascribed to Lithothamnion and reported from southern Australia. These include taxa whose status is uncertain, incorrect records, heterotypic synonyms of other species of Lithothamnion and taxa now known to belong to other genera or conspecific with taxa belonging to other genera.
The type of Goniolithon elatocarpum f. australasica Foslie (1901a, p. 19) (also see Woelkerling 1993, p. 33), collected in Western Port, Victoria, also belongs to Lithothamnion but is considered of uncertain status because the poor condition of the material does not allow for unequivocal determination at species level.
FOSLIE, M. (1901a). New melobesieae. K. norske Vidensk. Selsk. Skr. 1900(6), 1–24.
HEYDRICH, F. (1897b). Melobesieae. Ber. dt. bot. Ges. 15: 403–420, Plate 18.
ROSANOFF, S. (1866). Recherches anatomiques sur les Mélobésiées. Mem. Soc. Imper. Sci. Nat. Cherbourg 12, 5–112, Plates 1–7.
WILKS, K.M. & WOELKERLING, W.J. (1995). An account of southern Australian species of Lithothamnion (Corallinaceae, Rhodophyta). Aust. Syst. Bot. 8, 549–583.
WOELKERLING, W.J. (1983a). A taxonomic reassessment of Lithothamnium Philippi (Corallinaceae, Rhodophyta) based on studies of R.A. Philippi's original collections. Br. phycol. J. 18, 165–197.
WOELKERLING, Wm.J. (1988). The Coralline Red Algae. [British Museum (N.H.): London.]
WOELKERLING, Wm.J. (1993). Type collections of Corallinales (Rhodophyta) in the Foslie Herbarium (TRH). Gunneria 67, 1–289.
The Marine Benthic Flora of Southern Australia Part IIIB complete list of references.
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 LITHOTHAMNION
1. Roofs of mature tetrasporangial conceptacles pitted with depressions, each of which overlies a pore (Fig. 75B); tetrasporangial conceptacle pore canals bordered by cells that usually differ in size and shape from cells in other roof filaments (Fig. 75D)
1. Roofs of mature tetrasporangial conceptacles not pitted with depressions around pores (Fig. 76B); tetrasporangial conceptacle pore canals bordered by cells that do not differ in size and shape from cells in other roof filaments (Fig. 76D)
State Herbarium of South Australia