Electronic Flora of South Australia Family Fact Sheet

ORDER ULVALES Blackman & Tansley

Phylum Chlorophyta

Thallus tubular, membranous and monostromatic or distromatic, or of biseriate filaments, basally attached or occasionally free floating. Cells small, uninucleate, with a single laminate or cup-chaped parietal chloroplast usually not occupying the whole cell, with one to a few pyrenoids.

Reproduction: Reproduction by biflagellate or quadriflagellate zoospores and by biflagellate isogametes or anisogametes from unisexual or bisexual thalli, or by parthenogametes (Tanner 1981, p. 225)

Life history diplohaplontic and isomorphic; in some species only one phase present.

Taxonomic notes: This order includes the common foliose and tubular green algae of the genera Ulva and Enteromorpha (and other related genera), which are basically diplohaplontic and isomorphic in their life histories though some species apparently have lost one phase of the life history. Heteromorphic taxa (e.g. Monostroma) with a single-celled sporophyte (Codiolum stage) are considered to comprise a separate order but are not as yet recorded from southern Australia, though Chapman (1956, p. 377) records nine species from New Zealand. Prasiola is also sometimes included in the Ulvales (e.g. Bold & Wynne 1978) but is here regarded as belonging to a separate order.

Our knowledge of the species of Ulva and Enteromorpha on southern Australian coasts if not satisfactory; so far, it is morphologically based and most of the species are considered to be the same as those from Europe. Cultural and life-history studies involving crossing experiments, similar to those of Bliding (1963, 1968) on European species, are essential to give a firm knowledge of the taxa.

Chapman (1952; 1956, pp. 396, 398) described two segregate genera of Ulvaceae, Lobata which is based on the presence in central axial regions of enlarged cells and Gemina which frequently has cells in pairs. As Papenfuss (1960, p. 312) has also noted, the characters of these genera are unsatisfactory since the enlarged cells are only those forming internal rhizoids (as in most species of Ulva) while the pairing of cells is seen shortly after cell division. Chapman's figures of cell structure of G. letterstedtioidea and G. linzoidea are very similar to U. rigida.

References:

BLIDING, C. (1963). A critical survey of European taxa in Ulvales. Part I. Capsosiphon, Percursaria, Blidingia, Enteromorpha. Opera Bot. 8(3), 1–160.

BLIDING, C. (1968). A critical survey of European taxa in Ulvales, II. Ulva, Ulvaria. Monostroma, Kornmannia. Bot. Notiser 121, 535–629.

BOLD, H.C. & WYNNE, M.J. (1978). Introduction to the Algae: Structure and reproduction. (Prentice-Hall: New Jersey.)

CHAPMAN, V.J. (1952). New entities in the Chlorophyceae of New Zealand. Trans. R. Soc. N.Z. 80, 47–58, Plates 21–22.

CHAPMAN, V.J. (1956). The marine algae of New Zealand. Part I. Myxophyceae and Chlorophyceae. J. Linn. Soc. Bot. 55 (360), 333–501, Plates 24–50.

PAPENFUSS, G.F. (1960). On the genera of the Ulvales and the status of the order. J. Linn. Soc. Bot. 56, 303–318, Plates 1–6.

TANNER, C.E. (1981). Chlorophyta: Life histories. In Lobban, C.S. & Wynne, M. J. (Eds), The Biology of Seaweeds, Ch 6, pp. 218–247. Botanical Monogr. Vol. 17. (Blackwell: Oxford.)

The Marine Benthic Flora of Southern Australia Part I complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
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