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BIODIVERSITY REFERENCE
 
    Vaucheria DC.    


Kingdom: Chromista
Phylum: Xanthophyta – yellow-green algae
Class: Tribophyceae
   (Order: Vaucheriales)


British distribution (genus): Widespread and common, terrestrial, freshwater, estuarine and marine.
World distribution (genus): Presumed to be cosmopolitan.


Vaucheria species are common algae in various freshwater habitats, on soil (forming felt-like patches), on estuarine mud and amongst higher plants in saltmarshes. One British species, V. piloboloides, is described as "truly marine", growing near and sometimes below the low water mark in sheltered bays in S.W. England (Christensen, 1987).

The thallus is filamentous and siphonous, i.e. thallus consisting of multinucleate, branched tubes rather than subdivided by cross walls into normal cells. The central part of the filament is occupied by a large vacuole, the chloroplasts consequently parietal (i.e. layered adjacent to the cell wall) and tending to be aligned parallel to the filament axis. Christensen points out that the ability to stream cytoplasm and nutrients along the filament, unimpeded by cross walls, allows these algae to survive when part of the thallus is buried by silt in saltmarshes or when parts of the thallus are subject to partial dessication on a soil surface. Vaucheria can be regarded as a more successful colonist of terrestrial habitats than are most other filamentous algae.


single filament
branched filament with other epiphytes
 
filament at two focus positions
Tip of filament examined at ×500:
a: near-surface focus
b: focus through central plane showing presence of the central vacuole


As is typical of the Xanthophyta, Vaucheria contains chlorophyll a and c, and lacks chlorophyll b (which is characteristic of the Chlorophyta) and fucoxanthin (which is characteristic of the Chrysophyta and Bacillariophyta). Diagnostic details of the Xanthophyta are beyond the intended scope of this page but are set out in algal textbooks such as Van den Hoek (1995). Sexual reproduction is öogamous - öogonia contain single egg cells which are fertilized by motile gametes, spermatozoids, released from antheridia. Some species produce asexual motile, multiflagellate spores, synzöospores, which are considered to be composed of numerous zöospores that remain united in a single, composite structure.

There are a number of species of Vaucheria known in Britain. L.R Johnson & R. Merritt (in John et al., 2002) recognise 20 British species of freshwater and soils; Christensen (1987) recognised 15 British species of saltmarshes and other estuarine and marine habitats, with only three species common to both works. Hardy and Guiry (2006) list one additional species more recently recorded in Britain. Identification depends on details of antheridia and öogonia, so no specific name is suggested for the vegetative filaments shown as photographs here.

filament with epiphytes
 
Vaucheria filaments are colonised by numerous epiphytes. Here can be seen various green algae, clusters of attached diatoms and the long, fine filaments of actinomycetes.
 

Photographed material: free-floating in peaty water in Betula / Salix carr adjacent to a peat-bog on Gleniffer Braes, Renfrewshire, April 2001.


References
•   Christensen, T., (1987). Seaweeds of the British Isles, 4, Tribophyceae (Xanthophyceae), British Museum (Natural History), London.
•   Hardy, F.G., & Guiry, M.D., (2006). A checklist and atlas of the seaweeds of Britain and Ireland, revised edition. British Phycological Socity, London.
•   John, D.M., Whitton, B.A., & Brook, A.J., ed. (2002). The freshwater algal flora of the British Isles, Cambridge University Press, Cambridge.
•   van den Hoek, C., Mann, D.G., & Jahns, H.M., (1995). Algae: and introduction to phycology. Cambridge University Press, Cambridge.


© A.J. Silverside
Page first hosted at www-biol.paisley.ac.uk/bioref/, January 2003; transferred to lastdragon.org with minor edits, February 2011
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