Electronic Flora of South Australia Species Fact Sheet

Padina sanctae-crucis Boergesen 1914: 201, figs 153, 154.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae

Selected citations: Gaillard 1975: 85, figs 1–4. Taylor 1960: 237, pl. 34 fig. 2.

Thallus (Fig. 74A) medium brown throughout, lightly calcified, more so on the upper surface, 5–15 cm long and 5–25 cm in spread, when young flabellate, remaining so or becoming divided with flabellate to occasionally cuneate segments 1–5 cm broad above, with rounded axils, attached by a rhizoidal holdfast 0.5–2 cm long and 2–5 mm across; epilithic? Structure (Fig. 75I,J) of two layers of cells throughout, 100–150 µ thick near the apices and 150–200 µm thick below, with the upper cells (1.2–) 1.5–1.8 times the height of the lower cells. Cells in surface view of upper side 30–40 µm broad, L/B (1–) 1.5–2, on lower side 24–30 µm broad, L/B (1–) 1.5–2. Hairs (Fig. 75H) in alternating concentric lines on both sides of the thallus, 2–3 mm apart on each side, 20–25 µm in diameter.

Reproduction: Sporangia (Fig. 75H,I) in concentric, continuous or broken, relatively linear sori on the lower side of the thallus, above each of the hair lines but with alternate fertile and sterile zones when the hair lines on both sides are viewed together; indusium slight; sporangia ovoid, 140–170 µm long and 60–120 µm in diameter. Sexual plants unknown on Australian coasts, dioecious with sori of oogonia or antheridia (Gaillard 1975, fig. 4C,D).

Type from St Croix, West Indies; in C.

Selected specimens: South Passage, Shark Bay, W. Aust., 5 m deep (Cambridge, 16.viii.1979; ADU, A51771). 7 mile Beach, Dongara, W. Aust., 0.5–2 m deep (Kirkman, 17.ix.1979; ADU, A51303). Point Sinclair, S. Aust., drift, ( Womersley, 25.i.1951; ADU, A13892).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Tropics and subtropics of the eastern Atlantic; Japan.

In Australia, known from the west coast of Western Australia, with one specimen from Point Sinclair in South Australia.

Taxonomic notes: Gaillard (1975) has shown that P. japonica Yamada and probably P. haitiensis Thivy are not distinct from P. sanctae-crucis, and the western Australian plants agree well with this species. The sporangial sori are confined to the lower surface of the thallus, with a slight indusium, and when the hair lines on both surfaces are viewed, the sporangia are in fertile zones which alternate with sterile zones.

References:

BOERGESEN, F. (1914). The marine algae of the Danish West Indies. Vol. 1, Part 2. Phaeophyceae. Dansk bot. Ark. 2, 157–226.

GAILLARD, J. (1975). Padina sanctae-crucis Boergesen, Padina japonica Yamada, Padina haitensis Thivy et leurs affinités. Botaniste 57, 85–103.

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.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

Illustrations in Womersley Part II, 1997: FIGS 74A, 75 H–J.

Figure 74   enlarge

Fig. 74. A. Padina sanctae-crucis (ADU, A13892). B. Padina elegans (UWA, A962, holotype). C. Padina elegans (ADU, A19325).

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.

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