Electronic Flora of South Australia Genus Fact Sheet

Genus ASPARAGOPSIS Montagne 1841: xv

Phylum Rhodophyta – Class Florideophyceae – Order Bonnemaisoniales – Family Bonnemaisoniaceae

Thallus (gametophyte) erect, much branched with long, terete axes bearing dense, plumose laterals on all sides, the laterals densely covered with indeterminate branchlets and unbranched determinate ramuli; attachment by retrorsely spinous branches when epiphytic or by stolons when epilithic. Structure uniaxial, with a small but distinct apical cell and the subapical cells producing two opposite periaxial cells with a divergence of about ¼ on the axial cells, the larger of the two often forming a lateral indeterminate branch and the smaller often forming an unbranched determinate ramulus; the periaxial cells, whether forming a filament or not, cut off primary cortical cells laterally to form a continuous cortex which becomes several cells thick in older axes, with a space between the axial filament and the inner cortex in which sparse, branched, rhizoidal filaments develop upwards and downwards from periaxial cells on the swollen anterior ends of the axial cells. Determinate ramuli developing 5 cells around each axial cell, one the full length of the axial cell and two pairs of half-length cells (3 in sectional view of ramulus), with many of these cells cutting off on their inner side, by a strongly concave wall, a small gland cell.

Tetrasporophyte ("Falkenbergia" stage) tufted, 0.5–2 cm high, much branched, epilithic or epiphytic. Structure filamentous, with an axial cell and 3 pericentral cells of similar length, some cells also cutting off on their inner side a small gland cell.

Reproduction: Gametangial thalli monoecious or dioecious. Carpogonial branches 3-celled, with lateral nutritive cells from the lower cells, borne on a supporting cell on 1–3 subapical cells of a determinate lateral 9–11 cells long, reportedly with the gonimoblast originating from the hypogynous cell; carposporophyte developing a basal, branched, dendroid, fusion cell with branched gonimoblast filaments producing terminal, clavate, carposporangia. Pericarp developing early (pre-fertilization) and forming prominent, stalked, ostiolate cystocarps. Spermatangia borne on specialised ovoid heads, cut off from outer cells of compact cells surrounding an axial filament.

Tetrasporangia transformed from one of the pericentral cells of the tetrasporophyte, cruciately divided, released through a pore in the outer cell wall.

Life history triphasic, heteromorphic with a large gametophyte and small, filamentous tetrasporophyte.

Type species: A. delilei (Montagne) Montagne 1841: xiv. [= A. taxiformis (Delile) Trevisan]

Taxonomic notes: The life history and distinctive features of Asparagopsis and Falkenbergia were elucidated by Feldmann & Feldmann (1942), but it has been doubted whether the two taxa described below really are distinct species (see Dixon & Irvine 1977, p. 155). However, they are readily recognisable underwater at Rottnest I., W. Aust. (G.T. Kraft, pers. comm.).

References:

DIXON, P.S. & IRVINE, L.M. (1977). Seaweeds of the British Isles. Vol. 1, Rhodophyta. Part I, Introduction, Nemaliales, Gigartinales. [British Museum (N.H.): London.]

FELDMANN, J. & FELDMANN, G. (1942). Recherches sur les Bonnemaisoniacées et leur alternance de générations. Ann. Sci. Nat., Sér. 11 Bot. 3, 75–175.

MONTAGNE, C. (1841). Plantae cellulares. In Barker-Webb, P. & Bertholot, S., Histoire naturelle des Iles Canaries. Vol. 3, pp. 161–208, 1-xv, Plates 5, 7, 8.

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

Author: H.B.S. Womersley

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 ASPARAGOPSIS (GAMETOPHYTES)

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