Band 43, Heft 2

The fatty acid composition of large phylloids, small ones and air bladders of the brown alga Sargassum pallidum are reported. Different parts of the thallus of S . pallidum differed in content of polyunsaturated fatty acids of the n-6 family, especially in linoleic and dihomo-gammalinolenic acids (20:3 n-6). Small phylloids and air bladders contained much higher proportions of 20:3 n-6 (14.4 and 14.0% of total fatty acids, respectively) as compared with large phylloids (2.1 %). The distribution of the main n-6 and n-3 polyenoic fatty acids among individual lipids of large phylloids and air bladders of this alga are reported. The triacylglycerols were rich in dihomo-gammalinolenic acid compared to other lipids.

Both an intertidal and a subtidal population of Acanthophora najadiformis near the Cheradi Islands (Ionian Sea, Mediterranean Sea) were studied in order to know the life cycle of the species and both seasonal variation in plant size and the phenology of reproduction. The proportions of gametophytes, tetrasporophytes and propagule-bearing plants were analysed. Acanthophora najadiformis proved to be a perennial alga present only with the overwintering basal system in winter and spring and well developed fronds in summer and autumn, when it is the dominant species in the subtidal community. Differences in both plant size and reproductive plant number were detected between the intertidal and subtidal levels. In the intertidal zone plants grow faster and reach greater sizes than the subtidal ones; tetrasporophytes and propagule-bearing plants are more numerous than at the subtidal level. In both zones, tetrasporophytes seem to be dominant and propagule-bearing plants are by far the most numerous.

Long-term effects of full-spectrum solar radiation, solar radiation without UVB, and solar radiation without total UV (UVA + UVB) radiation were studied in intertidal Ulva rigida C. Agardh (Chlorophyta). The experiment was carried out under natural conditions and at prevailing winter levels of UV radiation. Changes in relative growth rate, photosynthesis and pigment content were studied after 7 and 20 d of cultivation under the three solar radiation conditions. Relative growth rate was enhanced (50 %) in the absence of UVB radiation after one week, but no difference was found after 20 d. Pigment content (chlorophyll a , chlorophyll b and carotenoids) was significantly higher in the presence of UVB, suggesting an efficient protective-pigment mechanism. When UVB was removed, photosynthetic performance measured as oxygen exchange and fluorescence parameters exhibited higher values than under the other treatments after 7 d of incubation. When samples were cultivated under PAR alone, photosynthetic performance was always negatively affected compared to in the presence of UV radiation. On the whole, intertidal U. rigida exhibited a remarkable capacity to cope with fluctuating light conditions.

Seasonal samplings were conducted at six sites on the northeastern coast of Baja California, Mexico, (between Campo Hawaii and Puertecitos), in the northern zone of the Gulf of California. A total of 140 taxa of marine algae were determined, of which 125 are cited for the first time for the area of study. The families with best representation are: Rhodomelaceae with 20 species, Corallinaceae with 16, Ceramiaceae with 11, Gracilariaceae with 9 and Dictyotaceae with 9. A higher diversity was found at the beginning of autumn, winter, at the end of spring, and a lower one in summer. Lower diversity was found at the sites located towards the north: Campo Hawaii with 12 species, El Machorro with 21 and El Faro de San Felipe with 44. These are places in which the beaches are broad and composed of sand and with few pebbles. A higher diversity was found at the sites located towards the south: El Coloradito with 75 species, Playa Santa Teresa with 76 and Puertecitos with 85. These localities are characterized by stable rocky substrates, with numerous intertidal pools. The most common species with regard to distribution and occurrence over time are: Cladophora prolifera, Struveopsis robusta, Dictyota flabellata, Gelidium pusillum, Gracilaria subsecundata, Prionitis abbreviata, Corallina vancouveriensis, Lithophyllum imitans, Spongites decipiens and Spyridia filamentosa . Twenty-one species are reported for the first time from the northern Gulf of California, and another three species represent new records for the Gulf: Gelidiocolax microsphaerica, Gastroclonium parvum , and Leathesia nana .

The sterol composition of these algae appeared to be very complex. While in Zanardinia prototypus the expected fucosterol predominated, Striaria attenuata contained significant amounts of lower sterol homologues (C 27 - and C 28 -sterols). Comparisons with the sterol composition of other algae were made and the data obtained was in agreement with some classifications proposed earlier. Significant differences have also been found in the lipid composition of these algae. Zanardinia prototypus contained mainly phospholipids, while the main lipid class in Striaria attenuata appeared to be monogalactosyl diacylglycerols. The concentrations of some of the individual fatty acids in the two algae also showed significant differences.

Sexual plants in the monotypic genus Ctenosiphonia Falkenberg and in two species of Polysiphonia Greville [ P. subulifera (C. Agardh) Harvey and P. flexella (C. Agardh) J. Agardh] are described for the first time in material collected from the Canary Islands. In Ctenosiphonia hypnoides (J. Agardh) Falkenberg cylindrical spermatangial axes replace both branches at the second dichotomy of fertile trichoblasts. The procarps arise on the second basal segment of a fertile trichoblast and consist of a 4-celled carpogonial branch, and two sterile-cell groups are borne on the supporting cell. Up to ten cystocarps are arranged in a series on the dorsal side of erect branches. Both Polysiphonia subulifera and P. flexella show spermatangial axes formed at the first dichotomy of fertile trichoblasts, replacing one branch and ending in 1–2 sterile terminal cells. Cystocarps are globose to pyriform in P. subulifera and spherical and flattened in P. flexella . Two species of Rhodomelaceae: Polysiphonia tepida Hollenberg and Womersleyella setacea (Hollenberg) R. E. Norris, and Aiolocolax pulchellus Pocock, related to Rhodomelaceae but of uncertain systematic position, are reported from the Canary Islands for the first time. Data concerning ecological conditions, geographical distribution, morphology and phenology are presented.

Ectocarpus , a cosmopolitan genus of filamentous marine brown algae, contains two species, E . siliculosus and E . fasciculatus . Both species are subject to virus infections, which either destroy the host's sporangia or persist in a latent state without visible symptoms. We used PCR amplification of a viral gene fragment to monitor the infection status of Ectocarpus samples from Gran Canaria Island, North Atlantic, and southern Chile over 26 months. At both sites, we found persistently high levels of pathogen prevalence: 40–100% of the Ectocarpus specimens from Chile and 55–100% from Gran Canaria contained viral DNA. No evidence for seasonal variation could be detected. We conclude that vertical transmission of viral DNA through mitotic zoospores of the host is the key mechanism for the persistence of the pathogen. The PCR amplification characteristics of samples from Gran Canaria indicate that two different virus genotypes coexist in the same host population.

Shoots of Posidonia oceanica were collected in the northwestern Mediterranean Sea, in a clean area: Villefranche-sur-mer, France, and in an area known for its mercury contamination: Rosignano, northwestern Italy. Foliar shoots of this phanerogam collected at Villefranche-sur-mer were treated for 48 h with different mercury concentrations (0; 0.01; 0.1 and 1 μg Hg L −1 ). Photosynthetic parts (adult and intermediate blades) showed a higher capacity for mercury uptake than that found in the sheaths. Glutathione S-transferase (GST) activities in foliar tissues of Posidonia oceanica from Rosignano were always higher than those from Villefranche-sur-mer. The mercury uptake experiment ( in vivo experiment) also showed an increase in GST activity as a function of mercury concentrations. This increase was higher in the photosynthetic parts. The GST activity was then measured in an in vitro experiment where different foliar tissues from both sampling sites were put in contact with mercury. A significant decrease in GST activity was observed as a function of mercury concentrations whatever the foliar tissue or the sampling site considered. This phenomenon allowed the determination of the IC 50 for mercury. The GST activities measured in Posidonia oceanica from the Rosignano area were more sensitive to mercury than samples from Villefranche-sur-mer. Foliar tissues also showed a different sensitivity to mercury; photosynthetic parts from Rosignano being more sensitive than basal parts. The kinetic parameters of GSTs were also determined in the sheaths of Posidonia oceanica from both sites. The results of the in vitro experiment seem to indicate that the isoenzyme composition of the GSTs may vary from one site or from one foliar tissue to another. The in vivo and in vitro effects of mercury appeared to be opposite. When Posidonia oceanica was exposed to mercury in the field or in vivo in the laboratory, both induction and inhibition of GST activities may have existed. Nevertheless, induction seemed to be the predominant process. Mercury may be involved in GST enzyme induction in this marine phanerogam and in the differences observed in GST activities in the field.

Allozyme variation was examined in 175 individuals representing 13 putative species of Sargassum from the Great Barrier Reef (GBR), Australia. Allozyme variability was low (five polymorphic loci, 12 alleles total), but differences between most morphological species were observed, and were generally greater than those between different geographical populations of the same taxon. Sargassum decurrens , S. oligocystum , S. parvifolium and S. swartzii + S. aquifolium , were clearly separated by fixed gene differences or major differences in allozyme frequencies, providing sound evidence of these species' reproductive isolation since they were sampled in sympatry. Sargassum siliquosum , S. fissifolium , S. ligulatum, and S. spinifex were not as clearly differentiated, but did form consistent groups, indicating some genetic support for their separation as species. It was clear that S. carpophyllum and S. polycystum are conspecific. Single populations of three different species were thought to be possible misassignments ( S. opacum = S. polycystum ; S. aquifolium = S. swartzii and S. linearifolium = S. fissifolium ), but may be morphological variants of the species with which they clustered. Finally, S. oligocystum (subgenus Eusargassum ) clustered with S. decurrens , (subgenus Phyllotrichia ) suggesting a revision of subgeneric boundaries in the genus Sargassum is required. Allozyme markers will be useful for species identification of Sargassum within the GBR, as many species are clearly distinguished morphologically for only a short time of the year when they have reproductive organs.

Six species of marine algae are reported from Malaysia for the first time and their characteristic features are described: Hildenbrandia rubra (Sommerfelt) Meneghini (Hildenbrandiales, Hildenbrandiaceae); Grateloupia filicina (Lamouroux) C. Agardh (Cryptonemiales, Halymeniaceae); Taenioma perpusillum (J. Agardh) J. Agardh, Taenioma dotyi Hollenberg and Zellera tawallina Martens (Ceramiales, Delesseriaceae), and Amansia rhodantha (Harvey) J. Agardh (Ceramiales, Rhodomelaceae). The occurrence of Taenioma dotyi in Malaysian waters is the first report outside the Hawaiian Islands. Amansia rhodantha is newly recorded for the Pacific Ocean. The presence of Gelidiella pannosa (Feldmann) Feldmann et G. Hamel (Gelidiales, Gelidiaceae) in Malaysia is confirmed.

Metapeyssonnelia corallepida sp. nov. from Florida and Belize is described. The species was collected overgrowing dead and living corals of the genera Millepora and Porites . It differs from the only previously described species of this genus, Metapeyssonnelia feldmannii , by its calcification, which is limited to the hypobasal layer, more or less well developed groups of cystoliths, the presence of conspicuous hairs, and an overall larger cell size. The discovery of tetrasporangial plants bearing nemathecia confirms that Metapeyssonnelia is a member of the Peyssonneliaceae.

The free sterols of the red alga, Chondria armata have been identified by means of NMR, EIMS and GCMS analyses. The mixture contained besides cholesterol, C 28 and C 29 saturated as well as unsaturated components. The major component present was 24β-ethyl cholesterol followed by cholesterol and 24-methylene cholesterol. Desmosterol was absent as were side chain oxygenated sterols.