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Two low intertidal assemblages dominated in 1977 by Bifurcaria bifurcata and Cystoseira baccata - Saccorhiza polyschides in the North coast of Spain show changes in the structure and dynamics after 30 years. A re-survey in 2007 detected phenological changes affecting the annual cycle of dominant canopy species. B. bifurcata has shortened its growth period and undergone a decrease in biomass, while C. baccata lengthened its period of growth and increased its biomass. Also important were the disappearance of Saccorhiza polyschides and the increase of Cystoseira tamariscifolia . These changes affect the rest of the species of the assemblages, with a shift in the main understory species and an increase in crustose coralline algae although the overall biomass of the subcanopy was similar. The species richness shows a sharp increase, at the expense of increasing epiphytes and simpler functional and morphological groups. These biological changes agree with the general trends of increasing sea surface temperature and the relaxation of the summer upwelling affecting the North coast of Spain, but the results were unexpected in the case of Bifurcaria bifurcata .

Phylogenetic relationships in the Sargassaceae were explored using three DNA markers, and the monophyly of its genera was challenged. Nineteen out of 24 currently recognized genera were sampled, representing 63 species. The variable mt23S-tRNA Val intergenic spacer could only be aligned within genera and could not be used to infer intergeneric relationships. The partial mt23S was also useful to delineate genera and was alignable at the family level but provided few informative characters. Analysis of mt23S DNA sequences together with chloroplast-encoded psbA sequences resulted in a better resolved phylogeny. Hormophysa was the first genus to branch off within the Sargassaceae, followed by Myriodesma; then the three genera Caulocystis, Carpoglossum, and Scaberia in unresolved order; and then Acrocarpia. The other taxa studied here were divided over three major clades, but there was no branch support for the monophyly of two of these. The genera Bifurcaria, Cystoseira, Halidrys, and Sargassum appeared polyphyletic. The following taxonomic changes are proposed: a new genus Brassicophycus for Bifurcaria brassicaeformis (Kutzing) E. S. Barton; reinstatement of the genus Sargassopsis for Sargassum decurrens (R. Brown ex Turner) C. Agardh; reinstatement of the genus Sirophysalis for Indo-Pacific Cystoseira trinodis (Forsskal) C. Agardh; reinstatement of the genus Polycladia for the western Indian Ocean species Cystoseira indica (Thivy et Doshi) Mairh, Cystoseira myrica (S. G. Gmelin) C. Agardh, and Acystis heinii Schiffner; and reinstatement of the genus Stephanocystis for the North Pacific Cystoseira species and Halidrys dioica N. L. Gardner. The European Cystoseira species should be split into three genera, but no name changes are proposed yet, because diagnostic characters were found only for the clade including the type species. Some evolutionary trends could be discerned from the mt23S + psbA phylogeny.

This review presents the chemistry of secondary metabolites isolated from the Cystoseiraceae and its contribution to the identification of species belonging to the major genera of this family. It completes Piattelli's review on the chemistry and taxonomy of Sicilian Cystoseira species which was presented at the Sixth International Symposium on Marine Natural Products, held in Dakar, 1989 [Piatelli, M. (1990) New J. Chem. 14, 777–782]. In particular, the chemical studies of Cystoseira species from Atlantic and some other Mediterranean Coasts are reported with those of other genera from the Cystoseiraceae family, such as Bifurcara, Halidrys and Cystophora. This review is limited to secondary metabolite—diterpenoids essentially—isolated from the lipid extract of studied species (literature up to January 1995).

International audience; The phenology of the introduced Sargassum muticum and two native species Bifurcaria bifurcata and Cystoseira baccata were monitored during eighteen months at two sites in Brittany. Density and length varied seasonally only in Sargassum. Larger individuals of Sargassum were observed in summer whereas in Cystoseira, they appeared almost in autumn. Peaks in maturity were delayed: in summer for Sargassum and in winter for Cystoseira and Bifurcaria. Phenolic contents increased before their respective reproductive period as a chemical defence. Moreover, size composition varied with site and season depending on species. In Sargassum, the quantity of small compounds decreased in summer together with an increase of 2000/5000 Da compounds. In Bifurcaria 2000/5000 Da compounds increased in summer (photoprotection) while in Cystoseira it increased in winter (protection for reproduction). Sargassum presented then a phenological plasticity not observed in native species. Moreover the three species possessed different chemical strategies to succeed in partitioning their vital space.

DNA SEQUENCE DATA DEMONSTRATE THE POLYPHYLY OF THE GENUS CYSTOSEIRA AND OTHER SARGASSACEAE GENERA (PHAEOPHYCEAE)

The algal family Cystoseiraceae (order Fucales, class Phaeophyceae) includes the genera Acrocarpia, Acystis, Bifurcaria, Bifurcariopsis, Carpoglossum, Caulocystis, Coccophora, Cystophora, Cystoseria, Halidrys, Hormophysa, Landsburgia, Myriodesma, Scaberia and Stolonophora. Among these Cystoseira and Cystophora, the richest in species, are the most representative of the family. Cystoseira is a genus of worldwide distribution with about 80% of the species occurring along the Mediterranean and adjoining Atlantic coasts, while Cystophora is limited to the coasts of Australia and New Zealand. Members of the genus Cystoseira generally synthesise tetraprenyltoluquinols. Compounds of the same structural type have also been isolated from species belonging to the genera Halidrys (northern coasts of England), Bifurcaria (coasts of the Galapagos Islands), and Cystophora. Some species of these last two also elaborate linear diterpenoids as do some Cystoseira species. Tetraprenyltoluquinols have never been found in Caulocystis and Acrocarpia, which instead accumulate acetogenins. Finally, Landsburgia is the sole genus which produces naphthoquinone derivatives. Phytochemical studies of the secondary metabolites of the remaining genera are not reported. The chemistry of secondary metabolites and their distribution in the family Cystoseiraceae will be illustrated, and some taxonomic implications will be discussed.

Four Sargassaceae genus presenting high biomass in Brittany and\or in the South Pacific were chosen as models of this study. The aims of this works were i) to understand the chemical ecology of Sargassaceae in temperate and tropical environment, ii) to characterize specific chemomarkers from certain species and iii) to identify potential bioactive molecules. Then, a pluridisciplinary work was carry out with the study of the chemical ecology of Sargassaceae, in Brittany on one hand, with the study of the spatio-temporal variations of certain defense compounds of Sargassum muticum, Bifurcaria bifurcata and Cystoseira baccata associated with an ecological survey of these species and in the South Pacific on the other hand, with the study of these same defense compounds within Turbinaria sp. and Sargassum sp from various sites. At the same time, two chemotaxonomical studies were led. On the Turbinaria genera to identify one or several chemomarker(s) allowing discriminating T. ornata and T. conoides. And on the other hand, on B. bifurcata to understand the geographical distribution of the existing chemical types within this species. Then, to answer the third objective of this work, three biological activities were looked for first and foremost within the studied species: cytotoxicity, anti-inflammatory activity and neurotoxicity. The results allowed i) to highlight the impact of the environmental conditions on the biological and ecological variables studied to these species in temperate and tropical environments; ii) to identify the acid turbinaric as a chemomarker of T. conoides and to highlight the existence of ecotypes from B. bifurcata ; iii) to report the anti-phospholipase A2 activity of fatty acids stemming from tropical seaweeds and the antiradical and antioxidant activities of eleganolone isolated from B. bifurcata ., Quatre genres de Sargassaceae présentant de forte biomasse en Bretagne et/ou dans le Pacifique Sud ont été choisi comme modèles de cette étude. Les objectifs étant i) de mieux comprendre l'écologie chimique des Sargassaceae en milieu tempéré et en milieu tropical, ii) de rechercher des chimiomarqueurs spécifiques à certaines espèces et iii) de rechercher de molécules potentiellement bioactives. Ainsi, un travail pluridisciplinaire a été entrepris avec l'étude de l'écologie chimique des Sargassaceae, en Bretagne d'une part, via l'étude des variations spatio-temporelles de certains composés de défenses synthétisés par Sargassum muticum, Bifurcaria bifurcata et Cystoseira baccata associé à un suivi écologique de ces espèces et dans le Pacifique Sud d'autre part, via l'étude de ces mêmes composés de défenses au sein de Turbinaria sp. et Sargassum sp provenant de différents sites. Parallèlement, deux études de chimiotaxonomie ont été menées. D'une part sur le genre Turbinaria afin d'identifier un ou des chimiomarqueur(s) permettant de discriminer T. ornata et de T. conoides. Et d'autre part sur B. bifurcata afin de mieux comprendre la répartition géographique des types chimiques existants au sein de cette espèce. Puis, pour répondre au troisième objectif de cette thèse, trois activités biologiques ont été recherchées en priorité au sein des espèces étudiées: la cytotoxicité, l'activité anti-inflammatoire et la neurotoxicité. Les résultats de cette étude ont permis i) de mettre en évidence l'impact des conditions environnementales sur les variables biologiques et écologiques étudiées chez ces espèces en milieu tempéré comme en milieu tropical ; ii) d'identifier l'acide turbinarique comme étant un chimiomarqueur de l'espèce T. conoides et de mettre en évidence l'existence d'écotypes chez B. bifurcata ; iii) de rapporter l'activité anti-phospholipase A2 d'acides gras issus d'algues du Pacifique Sud et l'activité antiradicalaire et antioxydante de l'éléganolone isolée chez B. bifurcata.

The algal family Cystoseiraceae (order Fucales, class Phaeophyceae) includes the genera Acrocarpia, Acystis, Bifurcaria, Bifurcariopsis, Carpoglossum, Caulocystis, Coccophora, Cystophora, Cystoseria, Halidrys, Hormophysa, Landsburgia, Myriodesma, Scaberia and Stolonophora. Among these Cystoseira and Cystophora, the richest in species, are the most representative of the family. Cystoseira is a genus of worldwide distribution with about 80% of the species occurring along the Mediterranean and adjoining Atlantic coasts, while Cystophora is limited to the coasts of Australia and New Zealand. Members of the genus Cystoseira generally synthesise tetraprenyltoluquinols. Compounds of the same structural type have also been isolated from species belonging to the genera Halidrys (northern coasts of England), Bifurcaria (coasts of the Galapagos Islands), and Cystophora. Some species of these last two also elaborate linear diterpenoids as do some Cystoseira species. Tetraprenyltoluquinols have never been found in Caulocystis and Acrocarpia, which instead accumulate acetogenins. Finally, Landsburgia is the sole genus which produces naphthoquinone derivatives. Phytochemical studies of the secondary metabolites of the remaining genera are not reported. The chemistry of secondary metabolites and their distribution in the family Cystoseiraceae will be illustrated, and some taxonomic implications will be discussed.

Summary The spermatozoids of three genera of Cystoseiraceae (Halidrys, Cystoseira and Bifurcaria) have been investigated electron microscopically with respect to their external morphology, and two of them (Cystoseira and Halidrys) also with respect to their microanatomy for the purpose of comparison with Fucus on the one hand and a brown algal zoospore on the other. Special attention has been devoted to the flagellar ‘root’ which is shown to be the homologue of the proboscis of Fucus and to be present also in the zoospore of Scytosiphon. Comparison between Scytosiphon, Dictyota and the Fucoids suggests that the true function of the flagellar root is not mechanical but metabolic or conductional, perhaps in some relation to respiration or gaseous exchange. The evidence is interpreted as giving strong support to the view that Fucus is not primitive but highly specialized and that Cystoseira has remained closer to an ancestral condition in a number of different characters.