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Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Family Delesseriaceae
Selected citations: De Toni 1900: 690. Huisman & Walker 1990: 430. Kylin 1924: 9. Lucas 1909: 36. Shepherd & Womersley 1971: 166; 1981: 366. Silva et al. 1996: 458. Womersley & Shepley 1982: 341, figs 2C, D, 9. Wynne 1989a: 514, 515, fig. 1A.
Synonyms
Delesseria dendroides Harvey 1855a: 548; 1860: pl. 137; 1863, synop.: xxxi. J. Agardh 1872: 58; 1876: 491. Sonder 1880: 24.
Membranoptera dendroides (Harvey) Kuntze 1891: 904.
Hydrolapatha dendroides (Harvey) Kuntze 1898: 410.
Thallus (Fig. 21A) medium to dark red, erect, 5–30 cm high, profusely branched to five or six orders with a heavily corticated, subterete, simple or furcate stipe to 10 cm long and 4–5 mm in diameter. The stipe is developed from the thickened lower midrib and is probably perennial since new fronds arise, often in a cluster, from its upper end. Annual fronds to 25 cm long, the primary blades up to 10 mm broad, bearing opposite pairs of secondary blades. This branching is repeated to the fifth order, all laterals being paired except the ultimate branchlets which are all developed abaxially. Branchlets elongate-ovoid to lanceolate, margins smooth or with irregular cellular projections formed by the simple elongation of occasional marginal cells. Holdfast lacerate or hapteroid, 0.5–1.5 cm across; epilithic. Structure. The lateral pericentral cells are formed within 3–5 segments of the apex (Fig. 16G). The transverse pericentral cells are formed 6–9 segments from the apex, being cut off almost simultaneously, but the adaxial one has been observed to form first (Fig. 16H). Only the innermost five or six cells of the second-order cell row produce third-order rows (Figs 16G, 21B, C) and different patterns of development are shown in later-formed blades, changing from the wide primary blades with 20–30 cells in cell rows between the midrib and margin to the narrow ultimate blades where there may be only two large lateral cells associated with each central cell. Near the apices of blades when growth is less active, the lateral pericentral cells form only one row of lateral cells, i.e. there are no third-order rows. The ultimate branches may show marginal (exogenous) branching or proliferation, but only of a very few cells. Midrib cortication is very heavy in the older blades but is variable between the orders of blades and ultimate blades are without midrib cortication. New blades arise from the central cells, but the initiation of a new lateral is preceded by formation of a corticating cell from the transverse pericentral cell; this is the first indication of new blade development. Cells mostly multinucleate; rhodoplasts discoid, in slight chains in larger cells.
Reproduction: Gametophytes dioecious. Procarps are developed on many successive segments of the blade, mainly abaxially, but a few segments near the tip of the blade may have procarps formed from both transverse pericentral cells. The procarp consists of one carpogonial branch of four cells and two groups of sterile cells (one 2-celled, one 1-celled) cut off from the supporting cell. Carposporophyte with a massive fusion complex, carposporangia elongate-clavate, 20–35 µm in diameter, formed singly from the cells of the much branched gonimoblast, maturing sequentially. In the fertile areas of the cystocarpic blades only one lateral cell row develops from each lateral pericentral cell. Cystocarps (Fig. 21D) form abaxially near the tips of penultimate blades. Mature cystocarps 800–1200 µm in diameter, ostiolate, subspherical with a thickened stalk that develops from the heavily corticated lower portion of the fertile blade. The tip of the fertile blade remains visible as a short 'spine' projecting backwards parallel with the stalk of the cystocarp. Pericarp of 2 (–3) layers of cells, the outermost rounded in outline and irregularly arranged; ostiole rim bounded by irregularly shaped cells, not sharply outlined. Spermatangia (one small blade only on AD, A46906 observed) form a central sorus (Fig. 21E) on both sides of blade, with transverse pericentrals, occasionally the lateral pericentrals, and several outer lateral cells undivided. Near the apices of the male blade the lateral pericentral cells produce only one row of cells, but two in fertile regions.
Tetrasporangia develop in regular sori (Fig. 21F) in the smaller blades and each lateral pericentral cell within the tetrasporangial region produces normally only a single row of cells, except occasionally near the margin of the blade. Tetrasporangia are cut off very soon after the two corticating cells (which may later subdivide) and develop in acropetal sequence from the lateral pericentral cells and later from the 1 or 2 adjacent lateral cells (occasionally also from abaxial pericentral cells). The cortical cells remain as a single layer and no corticating cells subsequently form tetrasporangia; thus the tetrasporangia lie in a regular pattern (Fig. 21F). Within the sorus the adaxial pericentral cell remains undivided while the abaxial pericentral cell cuts off first at least one cortical cell and then the tetrasporangial initial; tetrasporangia 50–80 (–180) µm in diameter.
Type from Fremantle, W. Aust., (Clifton); holotype in Herb. Harvey, TCD (Trav. Set 269).
Selected specimens: Eyre, W. Aust., drift (Parsons, 22.xi.1968; AD, A34435). Elliston, S. Aust., drift (Womersley, 13.i.1951; AD, A13547) and 7 m deep (Shepherd, 21.x.1970; AD, A37557). Pearson I., S. Aust., 18 m deep (Shepherd, 10.i.1969; AD, A34120). Point Avoid, Eyre Peninsula, S. Aust., drift (Womersley, 2.xii.1975; AD, A46906). 15 km SE of Cape Willoughby, Kangaroo I., S. Aust. 38 m deep (Bone, 13.iii.1989; AD, A59864).
Distribution: Fremantle and Rottnest I., W. Aust., to Point Avoid, Eyre Peninsula, S. Australia. A deeper water species, known from 6–38 m deep.
Taxonomic notes: Harvey (1860, pl. 137) and J. Agardh (1876, p. 491) recognised two varieties of H. dendroides. The first, a lancifolia, is typical of the species whereas the second, B oblongifolia, is probably not distinct.
H. dendroides is a distinctive species, especially in its regularly opposite branching, restricted number of third-order cell rows and the restriction of lateral cell row development in fertile areas of the blades. The formation, in these areas of both cystocarpic and sporangial blades, of normally only a single lateral cell row in each segment (i.e. third-order rows are absent) separates it from all other species except H. revolutum. Other distinctive features are the limited lateral blade development in the final orders of blades (frequently reduced to only the lateral pericentral cell and two 'flanking cells') and the occasional presence of irregular marginal branching in these younger blades.
While H. dendroides shows distinctive differences from one or more of the other species of Hypoglossum, each feature is shared by at least one other species, e.g. the restricted number of third-order rows in vegetative blades occurs in H. protendens, as does the restriction of tetrasporangia to the primary cells and also their formation from transverse pericentral cells. Restriction of third-order rows in fertile blades is also shown in H. revolutum. When the similarities in habit, blade development and most reproductive features are considered, it seems best to retain all the above species in Hypoglossum.
References:
AGARDH, J.G. (1872). Bidrag till Florideernes Systematik. Acta Univ. Lund 8, 1–60.
AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)
AGARDH, J.G. (1898). Species Genera et Ordines Algarum. Vol. 3, Part 3 - De dispositione Delesseriearum. (Gleerup: Lund.)
DE TONI, G.B. (1900). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 2. pp. 387–776. (Padua.)
HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Jr. Acad. 22, 525–566.
HARVEY, W.H. (1860). Phycologia Australica. Vol. 3, Plates 121–180. (Reeve: London.)
HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)
HUISMAN, J.M. & WALKER, D.I. (1990). A catalogue of the marine plants of Rottnest Island, Western Australia, with notes on their distribution and biogeography. Kingia 1, 349–459.
KUNTZE, O. (1891). Revisio generum Plantarum. Part II. 4. Algae, pp. 877–930. (Leipzig.)
KUNTZE, O. (1898). Revisio generum Plantarum. Part III. 2. Algae, pp. 385–437. (Leipzig.)
KYLIN, H. (1924). Studien über die Delesseriaceen. Lunds Univ. Årsskr. N.F. Avd. 2, 20(6), 1–111.
LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.
SHEPHERD, S.A. & WOMERSLEY, H.B.S. (1971). Pearson Island Expedition 1969.-7. The subtidal ecology of benthic algae. Trans. R. Soc. S. Aust. 95(3), 155–167.
SHEPHERD, S.A. & WOMERSLEY, H.B.S. (1981). The algal and seagrass ecology of Waterloo Bay, South Australia. Aquat. Bot. 11, 305–371.
SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (Univ. California Press: Berkeley.)
SONDER, O.W. (1880). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)
WOMERSLEY, H.B.S. & SHEPLEY, E.A. (1982). Southern Australian species of Hypoglossum (Delesseriaceae, Rhodophyta). Aust. J. Bot. 30, 321–346.
WYNNE, M.J. (1989a). A reassessment of the Hypoglossum group (Delesseriaceae, Rhodophyta), with a critique of its genera. Helgol. Meeresunters. 42, 511–534.
The Marine Benthic Flora of Southern Australia Part IIID complete list of references.
Publication:
Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.
Illustrations in Womersley Part IIIA, 2003: FIGS 16G, H, 21.
Figure 16 enlarge
Fig. 16. A. Hypoglossum revolutum (AD, A37017)). Cell lineages, cells of second-order rows stippled. B, C. Hypoglossum heterocystideum (AD, A32138). B. Juvenile blade. C. Cell lineages, mid blade. D. Hypoglossum harveyanum (AD, A49090). Cell lineages, mid blade. E. Hypoglossum armatum (AD, A49380). Cell lineages, mature blade. F. Hypoglossum protendens (AD, A42964). Cell lineages, mid blade. G, H. Hypoglossum dendroides (AD, A37557). G. Blade apex. H. Sectional views of apices and formation of transverse pericentral cells (as in Womersley & Shepley 1982, courtesy of Aust. J. Bot.).
Figure 21 enlarge
Fig. 21. Hypoglossum dendroides (A, A13547; B, F, AD, A37557; C, E, AD, A46906; D, AD, A34435). A. Habit. B. Blade apex showing segmentation. C. Blade with second- and third-order cell rows. D. Cystocarp. E. Blade with spermatangial sori. F. Upper part of tetrasporangial blade. (All as in Womersley & Shepley 1982, courtesy of Aust. J. Bot.)
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