Electronic Flora of South Australia Genus Fact Sheet

Genus DERBESIA Solier 1846: 452

Phylum Chlorophyta – Order Derbesiales – Family Derbesiaceae

Heteromorphic. Sporophytic thallus tufted, filamentous, subdichotomous to irregularly laterally branched, coenocytic apart from double septa at the base of some older laterals; chloroplasts numerous, usually crowded, lenticular, with or without a pyrenoid. Sporangia lateral, ovoid to pyriform, cut off by a basal wall plug, containing 20–30 stephanokontic zoospores (normally meiospores, occasionally mitospores). Gametophytic thallus ("Halicystis) globular to ovoid, coenocytic, with peripheral cytoplasm containing numerous lenticular chloroplasts with or without pyrenoids, producing biflagellate anisogametes from peripheral areas of cytoplasm.

Type species: D. marina (Lyngbye) Solier.

Taxonomic notes: A genus of several species showing marked heteromorphy between the filamentous, branched sporophyte and the ovoid gametophyte, which was earlier placed in a separate genus Halicystis Areschoug. Detailed morphological and life history studies are needed of the two taxa recognized for southern Australia, especially as to the size of chloroplasts and presence or absence of pyrenoids. Dried or liquid preserved material is of limited value for observations of the chloroplasts.

References:

SOLIER, A.J.J. (1846). Sur deux Algues zoosporées, formant le nouveau genre Derhesia. Rev. hot. 1, 452–454.

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 SPECIES OF DERBESIA

1. Filaments 30–40 µm in diameter, with double septa at bases of some older branches; chloroplasts 4–6 µm long, without a pyrenoid; sporangia 80–105(4 35) µm long, usually ovoid 1

D. marina

1. Filaments mostly 50–80 µm in diameter; without septa at bases of older branches; chloroplasts 6–10 (–16) µm long, with a pyrenoid; sporangia (1604200–300 (–400) µm long, usually narrowing markedly to their base

D. tenuissima


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