Electronic Flora of South Australia Species Fact Sheet
Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae
Zonaria gymnospora Kützing 1859: 29, pl. 71, fig. II.
Padina vickersiae Hoyt in Howe 1920: 595. Taylor 1960: 236, pl. 34, fig. 1.
Thallus (Fig. 73C) medium brown above to dark brown below, relatively robust, often lightly calcified on the upper surface, 5–15 cm long and 5–20 cm in spread, when young flabellate and becoming shallowly to deeply divided with cuneate to flabellate segments mostly 1–5 cm broad above, with acute to rounded axils, attached by a rhizoidal holdfast 0.5–2 cm long and 0.2–1 cm across; epilithic. Structure (Fig. 75B,C) of four layers of cells, 100–150 µm thick, near the apices, becoming 6–8 (–9) cells and 200–250 µm thick in lower parts with similar sized cells throughout in transverse section. Cells in surface view 25–30 µ broad, L/B 1–1.5 (–2). Hairs (Fig. 75A) in concentric lines, 3–6 mm apart, on both sides of the thallus, more conspicuous on the lower side, 25–35 µm in diameter.
Reproduction: Sporangia (Fig. 75A,B) in concentric lines, or more or less in rows of sori, between each hair line, indusium absent or slight, on both surfaces but mainly on the upper; sporangia ovoid but broad-based, 25–35 µm long and 10–15 µm in diameter. Sexual plants unknown on Australian coasts, reported by Taylor (1960, p. 236, as P. vickersiae) as dioecious.
Type from St Thomas, West Indies; in MEL, 583380.
Selected specimens: Point Clune, Rottnest I., W. Aust., 13–14 m deep (Walker, 6.xii.1984; ADU, A56635). Mandurah, W. Aust., drift (Oberlander, 21.i.1961; ADU, A24714). Bunker Bay, Cape Naturaliste, W. Aust., uppermost sublittoral ( Womersley, 2.ix.1979; ADU, A50599). Hamelin Bay, W. Aust., drift ( Womersley, 1.ix.1979; ADU, A50606). Augusta, W. Aust. (Baird, Jan. 1934; UWA).
Distribution: Widespread in the tropics and subtropics, extending into warm temperate waters on both eastern and western coasts of Australia.
From the west coast it extends around to Augusta on the south coast of Western Australia.
Taxonomic notes: This species was described by Koh (M.Sc. thesis, unpublished, 1970) as P. occidentalis on the Western Australian coast, but the material agrees well with P. gymnospora. As Allender & Kraft (1983, p.87) remark, it is close to P. crassa Yamada, but the latter supposedly differs in having sporangial sori only on the outer (lower) side of the thallus whereas P. gymnospora has them mainly (but not only) on the upper side.
ALLENDER, B.M. & KRAFT, G.T. (1983). The marine algae of Lord Howe Island (New South Wales): The Dictyotales and Cutleriales (Phaeophyta). Brunonia 6, 73–130.
HOWE, M.A. (1920). Algae. In Britton, N.L. & Millspaugh, C.F., The Bahama Flora. (New York.)
KÜTZING, F.T. (1859). Tabulae Phycologicae. Vol. 9. (Nordhausen.)
SONDER, O.W. (1871). Die algen des tropischen Australiens. Abh. Nat. Ver. Hamburg 5(2), 33–74, Plates 1–6.
TAYLOR, W.R. (1960). Marine algae of the eastern tropical and subtropical coasts of the Americas. (Univ. Mich. Press: Ann Arbor.)
The Marine Benthic Flora of Southern Australia Part II complete list of references.
Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
Illustrations in Womersley Part II, 1997: FIGS 73C, 75 A–C.
Figure 73 enlarge
Fig. 73. A. Lobospira bicuspidata (NRCC, 10623). B. Thal lus with tetrasporangia and released spores at lower left (ADU, A42264). C. Padina gymnospora (ADU, A50606). D. Padina fraseri (ADU, A56877).
Figure 75 enlarge
Fig. 75. A–C. Padina gymnospora (ADU, A50599). A. Longitudinal section of thallus, showing inrolled apex, hair lines and sporangial sori. B. Longitudinal section with a sporangial sorus. C. Transverse section of older thallus. D–G. Padina fraseri (ADU, A51069). D. Longitudinal section of thallus showing inrolled apex, hair lines and sporangial sori. E. Transverse section of young thallus. F. Transverse section of older thallus with rhizoids. G. Longitudinal section of thallus with a sorus of sporangia. H–J. Padina sanctae-crucis (ADU, A13892). H. Longitudinal section of thallus showing inrolled apex, hair lines and sporangial sori. I. Longitudinal section of thallus with a sorus of sporangia. J. Transverse section of older thallus. K–M. Padina elegans (ADU, A33329). K. Longitudinal section of thallus showing inrolled apex, hair lines and sporangial sori. L. Transverse section of young thallus. M. Longitudinal section of thallus with a sorus of sporangia.
State Herbarium of South Australia