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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Melobesioideae
Thallus encrusting, epigenous and completely affixed by cell adhesion; genicula absent. Structure pseudoparenchymatous with dorsiventral organisation throughout; construction dimerous, consisting of two distinct groups of cohering filaments/cells: a single ventral layer in which each filament is composed of palisade and/or non-palisade cells, and secondly epithallial cells or multicellular filaments arising dorsally and more or less perpendicularly from cells of ventral layer filaments; cell elongation characteristics uncertain; cells of adjacent filaments joined by cell-fusions, secondary pit-connections absent; epithallial cells terminating most filaments at thallus surface, distal walls rounded or flattened but not flared; haustoria and trichocytes unknown.
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. Carpogonia terminating 2- or 3-celled filaments arising from the female conceptacle chamber floor. Carposporophytes when mature apparently composed of one (or several?) inconspicuous fusion cell (or lacking an evident fusion cell) and several-celled gonimoblast filaments with terminal carposporangia. Spermatangial filaments unbranched, borne on the floor, walls and roof of male conceptacle chambers.
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 two bispores and possessing an apical plug that blocks a roof pore prior to spore release.
Type species: M. membranacea (Esper) Lamouroux 1812: 186. Basionym: Corallina membranacea Esper 1806: Corallina Tab. XII.
Taxonomic notes: Over 160 species and infraspecific taxa have at some stage been ascribed to Melobesia (Woelkerling 1988, p. 190). Many of these, including 13 species recorded from southern Australia (Wilks & Woelkerling 1991, pp. 527–529), are now known to belong to other genera. The number of true species of Melobesia remains uncertain, and reliable concepts for most species scarcely exist. Details relating to generic etymology, nomenclature, synonymy, infrageneric classification, etc. are provided by Woelkerling (1988, p. 186–191). This account of southern Australian species, including the type species, follows Wilks & Woelkerling (1991).
Notes on other taxa reported from southern Australia
Wilks & Woelkerling (1991, pp. 527–529) provide information on 13 additional species and infraspecific taxa that at some stage were ascribed to Melobesia and reported from southern Australia. These include taxa whose status is uncertain, taxa now known to belong to other genera and taxa that are conspecific with species belonging to other genera.
References:
ESPER, E.G.C. (1806). Fortsetzungen der Pflanzenthiere. Vol. 2, Part 10, pp. 25–48. (Raspe: Nurnberg.)
LAMOUROUX, J.V.F. (1812). Sur la classification des Polypiers coralligenès non entièrement pierreux. Nouv. Bull. Sci. Soc. Philom. Paris 3, 181–188.
WILKS, K.M. & WOELKERLING, W.J. (1991). Southern Australian species of Melobesia (Corallinaceae, Rhodophyta). Phycologia 30, 507–533.
WOELKERLING, Wm.J. (1988). The Coralline Red Algae. [British Museum (N.H.): London.]
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 MELOBESIA
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1. Mature tetrasporangial conceptacle roofs raised above or flush with surrounding thallus surface; pore-plate (Fig. 69E) composed of cells that are similar in size and shape to other roof cells; tetrasporangial initials situated one cell layer below the thallus surface; mature male and female-carposporangial conceptacle roofs (Fig. 70C, D) composed of short, squat cells | M. membranacea |
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1. Mature tetrasporangial conceptacle roofs flush with or slightly sunken below surrounding thallus surface; pore-plate (Fig. 71D) sharply differentiated from the remainder of roof, composed of cells that differ in size and shape from other roof cells; tetrasporangial initials situated five or more cell layers below the thallus surface; mature male and female-carposporangial conceptacle roofs (Fig. 72C, D) containing at least one layer of longer cells overlying layers of small, densely packed cells | M. rosanoffii |
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