Electronic Flora of South Australia Genus Fact Sheet

Genus VAUCHERIA De Candolle 1801: 20

Phylum Chrysophyta – Class Xanthophyceae – Order Vaucheriales – Family Vaucheriaceae

Thallus forming loose, soft, tufts or mats of entangled filaments usually anchored in mud or sand, often with lateral rhizoids, and commonly with erect, free, sparsely branched, filaments above. Filaments of fairly uniform diameter throughout, coenocytic (except near reproductive organs), with numerous nuclei and small discoid to ellipsoid chloroplasts, with or without pyrenoids; storage product oil. Growth of the filaments subapical.

Reproduction: Reproduction by asexual, ovoid to clavate, aplanosporangia or zoosporangia (in fresh water species), formed at the ends of filaments and cut off by a cross-wall, producing either a non-motile aplanospore which germinates by producing a slender vegetative filament, or a single, large, compound zoospore with numerous pairs of slightly unequal, smooth, flagella covering the surface.

Life history haplontic, with zygotic meiosis.

Type species: V. disperma De Candolle [= V. canalicularis (Linnaeus) Christensen 1968: 4661.

Taxonomic notes: Sexual reproduction oogamous; oogonia sessile or stalked, subspherical to ovoid or clavate and often beaked, producing a single egg which after fertilisation becomes the oospore (zygote) enclosed by a separate wall; antheridia conical to elongate, straight to reflexed, producing a large number of small, pale, sperm, each with two lateral flagella, the anterior-directed one with pinnate mastigonemes.

Vaucheria is a large genus of 60 or more species, largely fresh-water but with brackish and marine species. Vaucheria was considered to belong to the Chlorophyta until the 1950s when its photosynthetic pigments, food reserves and sperm flagella showed it is better placed in the Chrysophyta.

The following species occur in marine situations on southern Australian coasts, but others occur in brackish environments and may on occasion be covered by high tides. Christensen (1987b) discusses several species and Entwisle (1988) gives a thorough account of freshwater, brackish and marine species in south-eastern mainland Australia. Field collections of some species are often sterile, but usually produce sex organs when kept in culture; the latter, especially the antheridia, are essential for species determination.

References:

CHRISTENSEN, T. (1968). Vaucheria types in the Dillenian herbaria. Br. phycol. Bull. 3, 463–469.

CHRISTENSEN, T. (1987b). Some collections of Vaucheria (Tribophyceae) from southeastern Australia. Aust. J. Bot. (in press).

DE CANDOLLE, A.P. (1801). Extrait d'un rapport sur les Conferves, fait à la Société philomathique. Bull. Sci. Soc. Philom. Paris 3, 17–21.

ENTWISLE, T.J. (1988). A monograph of Vaucheria (Vaucheriaceae, Chrysophyta) in south-eastern mainland Australia. Aust. Syst. Bot. 1: in press.

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

KEY TO SPECIES OF VAUCHERIA

1. Antheridia borne directly on vegetative filaments, ovoid to short-cylindrical, opening by a terminal pore (Section Woroninia)

 2

1. Antheridia subtended by a basal, empty, cell, opening by one to several lateral pores on papillae (Section Piloboloideae)

3

2. Antheridia and oogonia adjacent on the one filament; antheridia ovoid, 80–140 µm long, L/D 1.4–2.5

V. velutina

2. Antheridia and oogonia on separate filaments; antheridia cylindrical to elongate-ovoid, (70–) 80–150 (–180) µm long, L/D (2–) 2.5–5 (–6)

V. conifera

3. Thalli monoecious, with oogonia and antheridia adjacent on vegetative filaments

V. piloboloides

3. Thalli dioecious or with oogonia and antheridia never adjacent on the one filament

4

4. Oogonia not subtended by a cell; no protoplasmic mass below the mature oospore; antheridia 300–500 (–600) µm long, single 4

V. longicaulis

4. Oogonia subtended by a cell; a protoplasmic mass present below mature oospore; antheridia 115–240 µm long, in small clusters

V. glomerata


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