Electronic Flora of South Australia Species Fact Sheet

Zosterocarpus australica Womersley sp. nov.

Phylum Phaeophyta – Order Ectocarpales

Thallus (Fig. 6A) medium brown, 1–2 cm long, much branched with long, bare filaments below and irregular, laterally branched tufts above. Filaments (Fig. 7A) 20–25 (–30) µm in diameter below, decreasing gradually to 10–15 µm in lesser branches which taper to 7–9 µm at base of the conical apical cells; mature cells (Fig. 7B) L/B (1–) 1.5–2.5 (–3); hairs absent. Growth by division of the apical cells (Fig. 7C) and by diffuse intercalary divisions elsewhere. Cells (Fig. 7B) with numerous discoid to ovoid phaeoplasts, without pyrenoids, and numerous centrally aggregated physodes.

Reproduction: Plurilocular sporangia (Fig. 7C,D) on lesser branches, commonly near the base of short laterals, 30–80 µm long, with 2–8 smaller cells cut off peripherally from each of 2–6 axial cells in an irregular manner; locules 4–8 µm across.

Holotype from Investigator Strait, S. Aust., 41 m deep, 35°24'S, 137°07'E ( Watson, 14.i.1971); in ADU, A38165.

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

Taxonomic notes: This southern Australian species agrees well with the type species from the Mediterranean but does not have the occasional swollen cells heavily packed with physodes as in the type (Feldmann & Feldmann 1947; Sauvageau 1931) and in Z. abyssicola, though physodes are frequent in all cells. Intercalary divisions seem to be much less frequent in the Australian species than in the type species.

Both the type species and Z. australica are deep-water plants, apparently rare.

References:

FELDMANN, J. & FELDMANN, G. (1947). Additions à la Flore des Algues marines de l'Algerie. Bull. Soc. Hist. Nat. Afr. Nord 38, 80–91.

SAUVAGEAU, C. (1931). Sur quelques Algues phéosporées de la rade de Villefranche (Alpes-Maritimes). Bull. Stn biol. Arcachon 28, 7–168.

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 6A, 7 A–D.

Figure 6   enlarge

Fig. 6. A. Zosterocarpus australica (ADU, A38165, holotype). B. Sorocarpus micromorus (MELU 20519; ADU, A39499). C. Pilayella littoralis (ADU, A42709). D. Feldmannia irregularis (A22596). E. Feldmannia paradoxa on Scytosiphon (A31828). F. Feldmannia globifera (A19777).

Figure 7   enlarge

Fig. 7. A–D. Zosterocarpus australica (ADU, A38165, holotype). A. Branch system bearing plurilocular sporangia. B. Mature cells with phaeoplasts and centrally aggregated physodes. C. Branchlet with apical cells and plurilocular sporangia, surface view. D. Ditto, median view. E–F. Sorocarpus micromorus (ADU, A39499). E. Branches with son of plurilocular sporangia. F. Cells with phaeoplasts and branch bearing clustered plurilocular sporangia. G–J. Pilayella littoralis (G–I, ADU, A42709; J, ADU, A55783). G. Branching pattern. H. Plurilocular sporangium intercalary on a branchlet. 1. Unilocular sporangia in branchlets. J. Filaments with rows of unilocular sporangia.

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