Electronic Flora of South Australia Family Fact Sheet

ORDER DERBESIALES Feldmann

Phylum Chlorophyta

Thallus heteromorphic, completely or largely coenocytic; sporophyte of free filaments, usually much branched; gametophyte either filamentous and relatively small, or ovoid and vesiculate; wall of sporophyte of mannan, but xylan in gametophyte; homoplastic, chloroplasts with or without pyrenoids and containing siphonein and siphonoxanthin.

Reproduction: Reproduction by multiflagellate (stephanokontic) zoospores from the sporophyte and biflagellate anisogametes from the gametophyte; or direct from the sporophyte. Reproductive organs become separated by plugs (Menzel 1980).

Life history diplohaplontic with heteromorphic generations.

Taxonomic notes: This is a small order of only a few genera, which are satisfactorily separated from the Caulerpales and Codiales by their heteromorphic life history, stephanokontic zoospores, and presence of mannan in the sporophyte wall but xylan in the gametophyte wall. Some authors (e.g. Bold & Wynne 1978, pp. 201, 206) retain the two families within the Caulerpales.

References:

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

MENZEL, D. (1980). Plug formation and peroxidase accumulation in two orders of siphonous green algae (Caulerpales and Dasycladales) in relation to fertilization and injury. Phycologia 19, 37–48.

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 FAMILIES OF DERBESIALES

1. Thallus with both gametophyte and sporophyte filamentous, the gametophyte much branched and usually with one or more axes; sporophyte usually only a few mm long, producing stephanokontic zoospores within the filaments

BRYOPSIDACEAE

1. Thallus with an ovoid, vesiculate gametophyte and filamentous subdichotomous to irregularly branched sporophyte (usually without distinct axes) bearing lateral sporangia cut off by a wall plug

DERBESIACEAE


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