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Name derivation:
Derbesia Solier = named for Professor Alphonse A. Derbés of Marseilles, a French phycologist
Classification:
Derbesia Solier 1846; there are 31 species of which 19 have been taxonomically accepted currently (Guiry and Guiry 2013). Order Bryopsidales; Family Derbesiaceae
Morphology:
Kornmann (1938) initially showed that Halicystis ovalis and Derbesia marina were life history phases of the same species. In the Northwest Atlantic D. marina populations have two types of life histories (Sears and Wilce, 1970). One involves a direct recycling by filamentous sporophytes (i.e. Derbesia), the other, which is apparently rare, involves an alternation with a haploid gametophyte (Halicystis ovalis). Sears and Wilce (1970) also showed that Halicystis could be obtained in culture directly from sporangia of D. marina sporangia Both phases are true coenocytes. Halicystis ovalis is spherical to subspherical, stalked and attached by rhizoids (siphons) that grow through holes in encrusting corallines (e.g. Phymatolithon laevigatum (Foslie) Foslie (cf. Figure -). It cells have numerous spherical to elliptical plastids with or without pyrenoids, and its cell walls contain xylan. Derbesia marina is an erect, dense, silky green brush-like tuft that attaches by rhizoids or a penetrating basal system. Filaments are dichotomously branched, and may have paired cross walls across each filament above a fork. Plastids are lens-shaped and are numerous per cell. Sporangia replace branches and are ovoid to pyriform. Stephanokont zoospores are large with up to 16 formed in each sporangium.
Similar genera:
Bryopsis
Habitat:
In the Northwest Atlantic populations of Halicystis ovalis are rare and only recorded from New Hampshire (Mathieson and Burns 1970) and the Passamaquoddy Bay area of eastern Canada (Tittley et al. 1987). They grow attached to crustose coralline algae [e.g. Phymatolitho laevigatum (Foslie) Foslie], often associated with Ptilota serrata Kützing and Corallina officinalis L. (cf. Figure -). Sporophytes are common to rare and are either pseudoperennials or aseasonal annuals; they occur on the open coast in the lower littoral zone (are often sponge covered) to 4-20m, either on crustose corallines or as epiphytes on other algae (e.g. Phyllophora ). They are able to regenerate from residual material growing within sponge tissues.
References:
Guiry, M.D. and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 2 August 2013. Kornmann, P. 1938. Zur Entwicklungsgeschichte von Derbesia und Halicystis. Planta 28: 464-470. Mathieson, A. C. and R. L. Burns 1970. The discovery of Halicystis ovalis (Lyngbye) Areschough in New England. J. Phycol. 6: 404-405. Sears, J. R. and R. T. Wilce 1970. Reproduction and systematics of the marine alga Derbesia (Chlorophyceae) in New England. J. Phycol. 6: 381-392. Tittley, I., W. F. Farnham, G. R. South and D. Keats 1987. Seaweed commnities of the Passamaquoddy region, southern Bay of Fundy, Canada. Brit. Phycol. J. 22: 313 (abstract).