Electronic Flora of South Australia Family Fact Sheet

ORDER PRASIOLALES Fritsch

Phylum Chlorophyta

Thallus foliose and monostromatic, or more or less terete and solid, commencing as a uniseriate filament but soon becoming 2–4 (–6) cells thick, basally attached by rhizoids. Cells small, uninucleate, in foliose taxa often arranged in square to rectangular groups separated by thicker walls, with a single somewhat stellate chloroplast containing a central pyrenoid.

Reproduction: Reproduction by the contents of upper cells being liberated as non-motile mitospores and by oogamy, with eggs and sperms liberated from groups of cells in the upper thallus following meiosis.

Life history diplontic, with meiosis occurring in upper thallus cells prior to gamete formation; or haplontic with zygotic meiosis.

Taxonomic notes: The Prasiolales (Schizogoniales of some authors) are sometimes ranked as a family of the Ulvales (e.g. Bold & Wynne 1978, p. 177) but the life history and reproduction (see Tanner 1981, p. 220), as well as their morphology and cell structure, separate them clearly as an order. The order includes a single family, Prasiolaceae (Rabenhorst) Borzi.

Two genera, Prasiola and Rosenvingiella, are currently placed in the family, and several authors (e.g. Bravo 1965, Edwards 1975) have suggested that the latter may be only a growth form of Prasiola. However, southern Australian collections are of one genus or the other, apparently with no admixture, and Kornmann & Sahling (1974), Hooper & South (1977, p. 385), and Hanic (1979) have presented evidence that they are distinct genera.

Both genera occur at a high intertidal to well above tidal level, often associated with bird colonies.

References:

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

BRAVO, L.M. (1965). Studies on the life history of Prasiola meridionalis. Phycologia 4, 177–194.

EDWARDS, P. (1975). Evidence for a relationship between the genera Rosenvingiella and Prasiola (Chlorophyta). Br. phycol. J. 10, 291–297.

HANIC, L.A. (1979). Observations on Prasiola meridionalis and Rosenvingiella constricta (S. & G.) Silva (Chlorophyta, Prasiolales) from Galiano Island, British Columbia. Phycologia 18, 71–76.

HOOPER, R. & SOUTH, G.R. (1977). Additions to the benthic marine algal flora of Newfoundland III, with observations on species new to eastern Canada and North America. Nat. can. 104, 383–394.

KORNMANN, P. & SAHLING, P.-H. (1974). Prasiolales (Chlorophyta) von Helgoland. Helgoländer wiss. Meeresunters. 26, 99–133.

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
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

KEY TO GENERA OF PRASIOLACEAE

1. Thallus foliose, usually 2–10 mm high, monostromatic 1

PRASIOLA

1. Thallus more or less terete, uniseriate when young, soon becoming 2–4 (–6) cells thick, solid

ROSENVINGIELLA


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