Search

The incorporation of coral species with massive (e.g., boulder, brain) morphologies into reef restoration is critical to sustain biodiversity and increase coral cover on degraded reef ecosystems. However, fragments and colonies of massive corals outplanted in Miami-Dade County, Florida, US, can experience intense predation by fish within the first week of outplanting, resulting in >70% mortality. Here, we tested for the first time the potential benefit of feeding corals powdered Dictyota, a brown reef alga that is chemically defended against grazing, to determine if exposure to Dictyota can confer chemical protection to coral fragments and reduce the impacts of fish predation after outplanting. We found that feeding corals every 2 to 3 days for 2 months with dried and powdered Dictyota prior to outplanting significantly reduced predation levels on Orbicella faveolata and Montastraea cavernosa fragments (with less than 20% of the fragments experiencing predation up to 1-month postoutplanting). We also found that a single exposure to Dictyota at a high concentration 1 to 2 days prior to outplanting significantly reduced predation for six coral species within the first 24 h following outplanting. Thus, feeding corals dry Dictyota ex situ prior to outplanting appears to confer protection from fish predation during the critical first days to weeks after outplanting when predation impacts are commonly high. This simple and cheap method can be easily scaled up for corals kept ex situ prior to outplanting, resulting in an increase in restoration efficiency for massive corals in areas with high fish predation. [ABSTRACT FROM AUTHOR]

The 1983 die-off of the long-spined sea urchin Diadema antillarum was linked to dramatic increases in macroalgal biomass and abundance on Caribbean coral reefs. D. antillarum densities have only recently begun to recover, and on some reefs this has led to a decrease in algae and an increase in coral recruits. Given the historic importance of this herbivore and the patchiness of its distribution on modern Caribbean reefs, a better understanding of its feeding preferences for different macroalgae is fundamental to reef ecology and management. This study investigated the feeding preferences of D. antillarum for different macroalgae and benthic cyanobacteria that were most common at our study sites on reefs of the U.S. Virgin Islands, although most of these algae occur throughout the Caribbean. Many of these algae are chemically rich, and some are known to be chemically defended against generalist grazers. Previous studies have suggested that D. antillarum has a greater capacity than herbivorous fishes and other herbivores to consume chemically defended algae. However, in this series of experiments, D. antillarum was more selective than expected in its food choices and avoided eating some macroalgae and cyanobacteria commonly found on shallow reefs of the U.S. Virgin Islands. Types of algae and their chemical extracts that deterred feeding include common brown algae (Dictyota and Lobophora spp.) and cyanobacteria (Dichothrix sp.). These feeding preferences have implications for coral reef ecosystems because some macroalgae and cyanobacteria can have negative effects on the survival of other organisms on reefs, including corals. [ABSTRACT FROM AUTHOR]

The genus Dictyota (Dictyotales, Phaeophyceae) comprises parenchymatous algae occurring predominantly in tropical to warm-temperate waters and has gathered attention due to its diverse secondary metabolites with antibiofouling and pharmaceutical potential, its oil content, and its potential as animal feed. This has resulted in an increase in economic potential during the last decade. In this review, we summarise the recent knowledge on the genus and concentrate on the applications and the economic potential of Dictyota. In addition, the review summarises the taxonomy, anatomy, cytology, genetic data, life history, chemical composition, nutritional value and ecological and economic importance of Dictyota species. Currently, around 100 species are recognised together with the morphologically similar and closely related genera Dilophus, Canistrocarpus and Rugulopteryx (tribus Dictyoteae). The thallus is characterised by one or more lens-shaped apical cells that divide into cortical and medullary cell layers. Species typically grow in rocky intertidal pools and subtidal areas. Dictyota is consumed locally in the Caribbean, Malayan-Indonesian and Hawaiian regions. Extracts of Dictyota which contain active compounds, such as diterpenes and phlorotannins, have been attributed antimicrobial, health and wellness promoting effects which render them promising candidates for the design of functional foods, phytomedicinal products, and cosmetics. The high fraction of lipids and fatty acids has propelled emerging applications in the biofuel industry and as a feedstock species. [ABSTRACT FROM AUTHOR]

The present study was intended to discover the preliminary phytochemicals of Dictyota dichotoma (Huds.) Lamouroux from Koothankuzhi coast, Tirunelveli district, the south east coast of Tamil Nadu, India. The preliminary phytochemical analysis was conducted in seven extracts namely methanol, acetone, chloroform, ethyl acetate, petroleum ether, hexane and benzene by Harborne method. The preliminary phytochemical analysis showed the presence of alkaloids, anthocyanin, anthraquinones, cardiac glycosides, catechin, coumarins, diterpenes, emodins, flavonoids, glycosides, leucoanthocyanin, lignins, phenols, phlobatannins, quinones, saponins, steroids, tannins, terpenoids and triterpenoids. Among the various phytochemicals studied, tannin showed the maximum presence, being found in seven different extracts and anthraquinones was observed in only one extract. From the results, it was noted that the extracts of Dictyota dichotoma (Huds.) Lamouroux was found to be the presence of a number of active secondary metabolites. This report will lead to the isolation and characterization of these active secondary metabolites for bioefficacy and bioactivity. [ABSTRACT FROM AUTHOR]

The decline of reef-building corals in conjunction with shifts to short-lived opportunistic species has prompted concerns that Caribbean reef framework-building capacity has substantially diminished. Restoring herbivore populations may be a potential driver of coral recovery; however, the impact of herbivores on coral calcification has been little studied. We performed an exclusion experiment to evaluate the impact of herbivory on Orbicella faveolata coral growth over 14 months. The experiment consisted of three treatments: full exclusion cages; half cage procedural controls; and uncaged control plates, each with small O. faveolata colonies. We found that herbivorous fish exclusion had a substantial impact on both macroalgal cover and coral growth. Fleshy macroalgae reached 50% cover within some exclusion cages, but were almost absent from uncaged control plates. Critically, O. faveolata calcification rates were suppressed by almost half within exclusion cages, with monthly coral growth negatively related to overgrowth by fleshy macroalgae. These findings highlight the importance of herbivorous fishes for coral growth and the detrimental impact of macroalgal proliferation in the Caribbean. Policy makers and local managers should consider measures to protect herbivorous fishes and reduce macroalgal proliferation to enable coral communities to continue to grow and function. [ABSTRACT FROM AUTHOR]

Copyright of Acta Biológica Colombiana is the property of Universidad Nacional de Colombia, Facultad de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to the great genetic diversity of HIV, producing an effective vaccine is extremely difficult. The combined antiretroviral therapy, although not leading to a cure, is capable of preventing opportunistic infections, since it greatly reduces HIV viral load in the blood. Considering a large number of HIV infections occur through sexual intercourse, the use of topical microbicides could be very useful tools to reduce infection rates. Studies by our group showed that the dolabelladienetriol, isolated from the brown seaweed Dictyota friabilis, had a clear effect on replication by inhibiting HIV-1 replication in cell culture. In this study, we have demonstrated that pretreatment with this compound for 2 h or 1 to 5 days, showed an inhibitory effect ranging from 60 to 90 % in peripheral blood cells (PBMC) and macrophages infected with HIV-1, respectively. Following the studies, we found that the dolabelladienetriol after being subjected to the experimental model of ex vivo cervical mucosa did not show toxicities in concentrations that were used for the experiments. Subsequently, we evaluate the protective effect of dolabelladienetriol in explant model in uterine cervix, showing a curve of dose-dependent inhibition in treatment with different concentrations of the compound in the presence of HIV-1 with 20 to 99 % in concentrations of 0.15 and 14.4 μM, respectively. These studies demonstrate the important effect of dolabelladienetriol that can be recognized as a microbicide. [ABSTRACT FROM AUTHOR]

Laminarans and fucoidans from two Russian Far-East ( Desmarestia viridis and Dictyota dichotoma) and four Vietnam species ( Dictyota divaricata, Padina boryana, Sargassum duplicatum, and S. feldmannii) of brown algae were isolated and studied. Water-soluble polysaccharides from D. divaricata, P. boryana, and S. feldmannii were mainly fucoidans; from D. viridis, D. dichotoma, and S. duplicatum, approximately equal amounts of laminarans and fucoidans. All studied laminarans had a main chain of 1,3-bonded glucose residues with branching on C-6 with various ratios of 1,3:1,6 bonds. Fucoidans from D. viridis and D. dichotoma were medium- and low-sulfated heterogeneous polysaccharides; from D. divaricata, P. boryana, S. duplicatum, and S. feldmannii, sulfated galactofucans containing traces of mannose, xylose, and glucose. Galactofucans from D. divaricata, P. boryana, S. duplicatum, and S. feldmannii were not cytotoxic and exhibited antitumor activity against DLD-1 human colon carcinoma cells. [ABSTRACT FROM AUTHOR]

Following a predation injury, one pufferfish (Arothron hispidus) had its upper jaw colonized with macroalgae. The fish has since lived for at least one year with this algal assemblage (unidentified red algae, Padina boryana and Dictyota bartayresiana). This algal proliferation caused a malformation of the fish jaw, raising the question of its survival with a physical defect in coral reefs, which are biodiversity but also predation hotspots. [ABSTRACT FROM AUTHOR]

While Dictyota dichotoma has been cultured for decades, relatively little is known on the abiotic regulation of its growth, life cycle and release periodicity. Here, we evaluated the different abiotic factors that potentially control growth, survival, fertility and spore release in order to establish efficient culture methods of the sporophyte that allow life cycle control. Vegetative growth is maximal at room temperature (18-20 °C), but cultures can be stored for months at low temperatures (≈8 °C). Red light, increased temperature and nutrient manipulation proved to be excellent triggers inducing sporogenesis. Sporophytes lack any lunar periodicity in spore release in contrast to gametophytes, but surprisingly, release of meiospores follows a similar diurnal cycle. This enables the production of synchronously developing spores during the entire lunar cycle. Interest in this species relates to its potential for commercial applications for phytoremediation, metabolites with therapeutic and anti-biofouling potential, and its usage as a model for developmental research complementary to Fucus. [ABSTRACT FROM AUTHOR]

The existence of massive cryptic diversity in algae makes linking DNA-based lineages to existing taxa exceedingly difficult. A better integration of historical collections into modern taxonomic research is therefore highly desirable. Using the brown algal genus Lobophora as a test case, we explore the feasibility of linking taxonomic names to clades in modern phylogenies. Despite Lobophora being a pantropical genus with probably more than 100 species, traditionally only a handful of species have been recognized. In this study we reevaluated the identity of 17 historical taxa thought to belong to Lobophora by attempting DNA amplification of herbarium material as well as specimens recently collected from the type localities (epitypes). In an attempt to assign them to Molecular Operational Taxonomic Units, the obtained sequences were integrated in a global Lobophora phylogeny based upon data derived from more than 650 specimens. Our results indicate that although five sequences were obtained from type specimens, exclusive reliance on information preserved in type specimens is problematic. Epitype material proved a more successful way forward, but this route often comes with a considerable degree of uncertainty, especially in tropical regions where the extent of sympatry among Lobophora lineages is often considerable. More problematic from a broader perspective is the fact that for 35% of historical taxa, either the type could not be traced or permission was not granted to extract DNA from the types. Such a low accessibility rate may reduce our reliance on type material and jeopardize future efforts to integrate historical taxa into a framework of a modern DNA-based taxonomy. [ABSTRACT FROM AUTHOR]

We investigated the spatial, seasonal, and within-plant variation in total fatty acids (TFA) and fatty acid (FA) composition in the brown seaweeds Dictyota bartayresii sampled from Nelly Bay, Orpheus Island, and Kissing Point (Northern Queensland, Australia) and Dictyopteris australis sampled from Nelly Bay. Both species were present year round, but with no consistent seasonal pattern in plant size, and had an annualized mean content of TFA of 5 % dry weight (dw) that is among the highest recorded for seaweeds. For Dictyota, larger plants had a higher content of TFA and a higher proportion of polyunsaturated omega-3 FA (PUFA(n-3)) than smaller plants, while for Dictyopteris, the TFA content and the proportion of PUFA(n-3) were unrelated to plant size. TFA in Dictyota varied considerably between locations (~40 %) (3.5-5.5 % dw) and to a lesser degree between seasons (~10 %) with a lower content of TFA and higher proportion of PUFA(n-3) in winter. Dictyopteris had an ~10 % higher content of TFA in winter but with no seasonal pattern in the composition of FA. There was also within-plant variation in FA, as TFA decreased from the tips toward the base in both species, and in Dictyopteris, the tips had a higher proportion of saturated FA (SFA) and PUFA(n-3) than the base. The presence of site- and species-specific variation in the content and composition of fatty acids reinforces the need for detailed analyses of the biochemical profile of seaweed biomass, including their extracts or purified compounds, if the focus is nutritional applications based on lipids. [ABSTRACT FROM AUTHOR]

Ocean acidification studies in the past decade have greatly improved our knowledge of how calcifying organisms respond to increased surface ocean CO levels. It has become evident that, for many organisms, nutrient availability is an important factor that influences their physiological responses and competitive interactions with other species. Therefore, we tested how simulated ocean acidification and eutrophication (nitrate and phosphate enrichment) interact to affect the physiology and ecology of a calcifying chlorophyte macroalga ( Halimeda opuntia (L.) J.V. Lamouroux) and its common noncalcifying epiphyte ( Dictyota sp.) in a 4-week fully crossed multifactorial experiment. Inorganic nutrient enrichment (+NP) had a strong influence on all responses measured with the exception of net calcification. Elevated CO alone significantly decreased electron transport rates of the photosynthetic apparatus and resulted in phosphorus limitation in both species, but had no effect on oxygen production or respiration. The combination of CO and +NP significantly increased electron transport rates in both species. While +NP alone stimulated H. opuntia growth rates, Dictyota growth was significantly stimulated by nutrient enrichment only at elevated CO, which led to the highest biomass ratios of Dictyota to Halimeda. Our results suggest that inorganic nutrient enrichment alone stimulates several aspects of H. opuntia physiology, but nutrient enrichment at a CO concentration predicted for the end of the century benefits Dictyota sp. and hinders its calcifying basibiont H. opuntia. [ABSTRACT FROM AUTHOR]

We investigated the potential of seaweeds as feedstock for oil-based products, and our results support macroalgae (seaweeds) as a biomass source for oil-based bioproducts including biodiesel. Not only do several seaweeds have high total lipid content above 10% dry weight, but in the brown alga Spatoglossum macrodontum 50% of these lipids are in the form of extractable fatty acids. S. macrodontum had the highest fatty acid content (57.40 mg g−1 dw) and a fatty acid profile rich in saturated fatty acids with a high content of C18:1, which is suitable as a biofuel feedstock. Similarly, the green seaweed Derbesia tenuissima has high levels of fatty acids (39.58 mg g−1 dw), however, with a high proportion of PUFA (n-3) (31% of total lipid) which are suitable as nutraceuticals or fish oil replacements. Across all species of algae the critical parameter of fatty acid content (measured as fatty acid methyl esters, FAME) was positively correlated (R2 = 0.67) with total lipid content. However, the proportion of fatty acids to total lipid decreased markedly with total lipid content, generally between 30% and 50%, making it an inaccurate measure of the potential to identify seaweeds suitable for oil-based bioproducts. Finally, we quantified within species variation of fatty acids across locations and sampling periods supporting either environmental effects on quantitative fatty acid profiles, or genotypes with specific quantitative fatty acid profiles, thereby opening the possibility to optimize the fatty acid content and quality for oil production through specific culture conditions and selective breeding. [ABSTRACT FROM AUTHOR]

The methanol extract of an assemblage of Halimeda stuposa and a Dictyota sp., yielded three natural products characteristic of Dictyota sp., and one of Halimeda sp. These included the xenicane diterpene 4-hydroxydictyolactone (1), and the diterpenes dictyol E (2), 8α,11-dihydroxypachydictyol A (3) and indole-3-carboxaldehyde (4). A minor revision of 1 and new spectroscopic data for 1 and 2 are provided, along with associated anti-cancer activities of compounds 1-4. [ABSTRACT FROM AUTHOR]

Two new species of the genus Rissoella Gray, 1847 are described from Venezuela, one from the National Park Morrocoy, Rissoella morrocoyensis sp. n. and the other from the Wildlife Refuge Isla de Aves, Rissoella venezolanicola sp. n. R. morrocoyensis sp. n. has a deep umbilicus (partly closed), preumbilical cord, black head, hypobranchial gland marked by a pale yellow boomerang-shaped ribbon and it lives on the leaves of the seagrass Thalassia testudinum Banks & König, 1805. R. venezolanicola sp. n. has an angled preumbilical cord which extends to the columella delimiting a trapezoid, a hypobranchial gland marked by a yellow quaver-shaped ribbon and protoconch with fuchsia highlights. It lives on the brown alga Dictyota spp. The records of Rissoella in the Caribbean are revised and illustrations, a comparative table and a key to the Caribbean species known for the genus are provided. [ABSTRACT FROM AUTHOR]

Several associations between marine organisms have been hypothesised to be chemically mediated, but few examples have been experimentally investigated to date. In the Brazilian littoral, the presence of Dictyota species living on various species of Sargassum is a very common feature, and here we present experimental evidence that the association between the brown seaweeds Dictyota sp. and Sargassum furcatum is chemically mediated. When separated but offered simultaneously to the herbivorous sea urchin Lytechinus variegatus, S. furcatum was more highly consumed than Dictyota sp. However, when S. furcatum was tied to Dictyota sp., it was significantly less consumed by L. variegatus. Crude extracts of Dictyota sp. were significantly less consumed by L. variegatus than were extracts of S. furcatum when the extracts were offered individually or paired. Plastic mimics of Dictyota sp. did not provide protection against consumption of S. furcatum by L. variegatus, confirming that S. furcatum protection was due to Dictyota sp. chemicals. Associational defense is defined as protection gained by an organism from living in association with another species. Clearly, chemicals produced by Dictyota sp. can provide an associational refuge. Considering that Dictyota species are frequently found growing epiphytically on many benthic species, associational defenses involving Dictyota spp. may be an important aspect to the structure and dynamics of many coastal communities. [ABSTRACT FROM AUTHOR]

We studied development of the cytokinetic diaphragm (i.e., the membranous septum formed during cytokinesis) in vegetative cells of the brown algae Sphacelaria rigidula, Halopteris congesta and Dictyota dichotoma after cryofixation-freeze-substitution. Cytokinesis began by the gathering of organelles and large vesicles between daughter nuclei following telophase. Subsequently, a thin cytoplasmic strand was formed along this plane, where endoplasmic reticulum (ER), dictyosome vesicles and particular membranous elements, the flat cisternae, were accumulated. Their fusion formed a patchy diaphragm with irregular gaps. Fine tubular channels perforated the diaphragm during all stages of its formation. Following diaphragm completion, cell wall material was deposited in it. The new walls had ER-free plasmodesmata. In D. dichotoma, diaphragm development did not follow a definite pattern, i.e., centripetal or centrifugal, a phenomenon also confirmed in H. congesta. In contrast, in apical cells of S. rigidula the diaphragm started developing from the periphery, growing to some extent centripetally. In these cells, local cell wall deposition was greatest at the division site. In apical cells in which cytokinesis was experimentally inhibited a ring of wall material was usually deposited at the cytokinetic plane. [ABSTRACT FROM AUTHOR]

Although a broad variety of classes of bioactive compounds have already been isolated from seaweeds of the genus Dictyota, most different species are still chemically and biologically unexplored. Dictyota species are well-known brown seaweeds belonging to the Dictyotaceae (Phaeophyta). The phytochemical composition within the genus Dictyota has recently received considerable interest, and a vast array of components, including diterpenes, sesquiterepenes, sterols, amino acids, as well as saturated and polyunsaturated fatty acids, have been characterized. The contribution of these valued metabolites to the biological potential, which includes anti-proliferative, anti-microbial, antiviral, antioxidant, anti-inflammatory, and anti-hyperpigmentation activities, of the genus Dictyota has also been explored. Therefore, this is the most comprehensive review, focusing on the published literature relevant to the chemically and pharmacologically diverse biopharmaceuticals isolated from different species of the genus Dictyota during the period from 1976 to now. [ABSTRACT FROM AUTHOR]

Dilophus okamurae, a common species of brown alga in the warm temperate western Pacific Ocean (Philippines, Taiwan, China, Korea and Japan), is characterized by a typical vegetative morphology that would support its traditional placement in the genus Dilophus. The species has a unilayered cortex, and the medulla is multilayered at least near the margins of the thallus. Sporangia on a two-celled stalk, without an involucrum, however, indicate a close relationship with the recently described genus Rugulopteryx. Molecular phylogenetic analyses, based on three separate loci, large subunit rDNA (LSU), rbcL and psbA confirm the close phylogenetic relationship between D. okamurae and R. radicans, and R. marginatus and R. suhrii. A transfer of D. okamurae to the genus Rugulopteryx is therefore proposed. Contrary to the expected diplobiontic life cycle, typically encountered in Dictyotales, the species exhibits an asexual life cycle consisting of sporophytes only in the populations studied on the east and south coast of Korea. Gametophytes were only obtained by culturing field collected specimens. [ABSTRACT FROM AUTHOR]

The late-nineteenth/early-twentieth century debate over homologous versus antithetic alternation of generations is reviewed. Supporters of both theories, at first, used Coleochaete as a model for the origin of land-plant life cycles. The early debate focused on the morphological interpretation of the sporophyte and on whether vascular cryptogams had bryophyte-like ancestors. The terms of the debate shifted after the discovery that the alternation of morphological generations was accompanied by an alternation of chromosome number. Supporters of homologous alternation now promoted a model in which land plants had been derived from an algal ancestor with an isomorphic alternation of haploid and diploid generations whereas supporters of antithetic alternation favored a model in which land plants were derived from a haploid algal ancestor with zygotic meiosis. Modern evidence that embryophytes are derived from charophycean green algae is more compatible with an updated version of the antithetic theory. [ABSTRACT FROM AUTHOR]

Two new diterpenes, (1E,2R*,3R*,4S*,6E,18S*)-4,18-dihydroxydictyolactone (1) and 8α,11-dihydroxypachydictyol A (2), together with fucoxanthin (3) and a known diterpene 4α-hydroxycrenulatane (4) were isolated from the methanol extract of the brown alga Dictyota sp. collected from Bangsaen Beach, Thailand. Their structures were determined by spectroscopic data. The relative stereochemistry of 1 was established by NOE difference and NOESY experiments. Compound 1 showed weak anti-tuberculosis activity while 2 displayed strong cytotoxicity against the NCI-H187 cell line, and potent anti-malarial activity. In addition, 3 was active against HSV-1 and malarial parasites. [ABSTRACT FROM AUTHOR]

Dictyota is a genus of tropical to warm temperate brown algae characterized by parenchymatous, flattened thalli that grow from a single, transversely oriented apical cell. Dictyota is currently distinguished from allied genera of the tribe Dictyoteae ( Dilophus, Glossophora, Glossophorella, and Pachydictyon) by the structure of the cortical and medullary layers, as well as the relative abundance of surface proliferations. Even though the traditional classification of the Dictyoteae has repeatedly been criticized in the past, the absence of sound molecular data has so far discouraged any new taxonomic proposals apart from a merger of Dilophus with Dictyota, which has been accepted by only part of the phycological community. Phylogenetic analysis of rbcL gene, partial 26S rDNA sequence, and combined data sets, including four of five generitypes, demonstrates that the traditional classification does not accurately reflect the evolutionary history of the group. None of the genera are resolved as a monophyletic clade. Hence, a merger of Glossophora, Glossophorella, and Pachydictyon in Dictyota is proposed. Two new genera, Canistrocarpus (incorporating D. cervicornis, D. crispata, and D. magneana) and Rugulopteryx (accommodating D. radicans, Dil. suhrii, and Dil. marginata), are proposed. Both genera are supported by molecular indications and a combination of reproductive and vegetative characters. The position of Dil. fastigiatus as a clade sister to Dictyota s.l. and the absence of Dil. gunnianus, the generitype of Dilophus, from the analyses, prevented us from making a more definite statement on the status of the latter genus. [ABSTRACT FROM AUTHOR]

Growth, survivorship, recruitment, and reproduction of Halimeda tuna, a dominant green alga in many reef systems of the Florida Keys, were monitored at a shallow back reef (4–7m) and deep reef slope (15–22 m) on Conch Reef. Despite lower light intensities and similar grazing pressures, amphipod infestations, and epiphyte loads at both sites, the deeper site exhibited significantly higher growth rates in summer months over a 4-year period than found for the shallow population, possibly because of higher nutrient levels at depth and photoinhibition of shallow plants. Sexual reproductive events occurred simultaneously across the entire reef, with up to 5% of the population at both sites developing gametangia. New upright axes formed from zygotes, asexual fragmentation, or vegetative runners. Plants appear to have persistent basal stumps that survive harsh environmental conditions, even if upright, photosynthetic axes are removed. Sexual reproduction and `smothering' by epiphyte overgrowth are hypothesized to be two causes of death for individuals. [ABSTRACT FROM AUTHOR]

Ciguatera poisoning (CP) poses a significant threat to ecosystem services and fishery resources in coastal communities. The CP-causative ciguatoxins (CTXs) are produced by benthic dinoflagellates including Gambierdiscus and Fukuyoa spp., and enter reef food webs via grazing on macroalgal substrates. In this study, we report on a 3-year monthly time series in St. Thomas, US Virgin Islands where Gambierdiscus spp. abundance and Caribbean-CTX toxicity in benthic samples were compared to key environmental factors, including temperature, salinity, nutrients, benthic cover, and physical data. We found that peak Gambierdiscus abundance occurred in summer while CTX-specific toxicity peaked in cooler months (February–May) when the mean water temperatures were approximately 26–28 °C. These trends were most evident at deeper offshore sites where macroalgal cover was highest year-round. Other environmental parameters were not correlated with the CTX variability observed over time. The asynchrony between Gambierdiscus spp. abundance and toxicity reflects potential differences in toxin cell quotas among Gambierdiscus species with concomitant variability in their abundances throughout the year. These results have significant implications for monitoring and management of benthic harmful algal blooms and highlights potential seasonal and highly-localized pulses in reef toxin loads that may be transferred to higher trophic levels. [ABSTRACT FROM AUTHOR]

Because herbivory is more intense in the tropics, tropical seaweeds may be better defended against herbivory than are temperate seaweeds. A “diffuse” coevolutionary corollary to this hypothesis is that tropical herbivores should be more resistant to seaweed defenses than temperate herbivores because tropical herbivores more commonly encounter heavily defended seaweeds. We begin to test the latter prediction using three newly discovered diterpenoid secondary metabolites from the tropical brown alga Dictyota acutiloba. We tested the feeding deterrent properties of these compounds against common herbivorous fishes and sea urchins from warm-temperate North Carolina versus tropical Guam using standardized laboratory feeding assays. The temperate herbivores were deterred by lower concentrations of secondary metabolites than the tropical herbivores. In no case was a tropical herbivore more deterred by a compound than a temperate herbivore, suggesting that temperate herbivores may be more strongly affected by seaweed chemical defenses. Feeding by the temperate pinfish Lagodon rhomboides was significantly reduced by two of the three diterpenes at a concentration that was only 13–18% of the natural concentration found in the alga. Feeding by four species of tropical fishes (two parrotfishes and two surgeonfishes) was unaffected by metabolite concentrations that deterred the temperate fish. At 100% of natural concentrations, only one of the three compounds deterred the two parrotfishes, and none of the three compounds deterred the surgeonfishes. Contrasts between the temperate sea urchin Arbacia punctulata and the tropical sea urchin Diadema savignyi showed a similar pattern; low concentrations of acutilol A acetate strongly deterred the temperate, but not the tropical, urchin. Tropical herbivores appear more resistant than temperate herbivores to seaweed chemical defenses. [ABSTRACT FROM AUTHOR]

Two bioassays (fish mortality and fish erythrocyte hemolysis) were used to survey for the presence of toxic principles in aqueous extracts of 19 species of marine macroalgae found in south Florida coastal waters. Extracts from six species (Chlorophyta -- Anadyomene stellata (Wulfen) C. Ag., Caulerpa prolifera (Forsskaål) Lamour.,. Penicillus capitatus Lamarck: Rhodophyta --Centrocer-as clavulatum (C. Ag.) Montagne, Laurencia papillosa (Forsskaål) Grev., L. poitel (Lamour.) Howe) showed lethal toxicity to the spotfin majarra. Euconistomus argenteus Baird & Girard. Extracts from three species (Chlorophyta -- A. stellata: Phacophyta -- Dictyota dichotoma (Hudson) Lamour Rhodophyta -- Wrangelia penicillata C. Ag.) lysed erythrocytes of sea bream, Archosargus rhomboidalis (L.). [ABSTRACT FROM AUTHOR]

The mechanism of yearly repopulation of Dictyota dichotoma (Hudson) Lamouroux in the inshore waters of North Carolina was studied in the field and in laboratory experiments. It was demonstrated that D. dichotoma is maintained throughout the year at this location and does not require yearly immigrations. A young germling stage was shown to function as the overwintering structure. Although release of aplanospores was unaffected by temperature and photoperiod, subseqeunt germination and establishment required warm conditons. If germlings were allowed to grow to the 7-9 cell stage under summer conditions, they could survive 21 wk of winter conditions. Transfer of 21 wk old winterized germlings to summer conditions resulted in the rapid production of erect blades. It therefore appears that D. dichotoma maintains its populations near its northern distribution limit on the East Coast of North America by undergoing dormancy after germling establishment. [ABSTRACT FROM AUTHOR]

Within-plant variation in the concentration of secondary metabolites, nutritive value, toughness, and susceptibility to herbivory was assessed for the brown alga Dictyota ciliolata. When young apices and older tissue from the same plant were offered in equal abundance to the herbivorous amphipod Ampithoe longimana and the sea urchin Arbacia punctulata, young apices were consumed about 2 times more than older tissue. Compared to young apices, the less preferred older tissue had a less palatable lipophilic extract, significantly higher concentrations of two secondary metabolites (another secondary metabolite did not differ significantly), 33% more soluble protein, and was 233% tougher. Higher levels of chemical defenses in older tissues, and not tissue toughness or nutritive value, appear to be responsible for the preference of Ampithoe longimana for young apices. The pattern of lower levels of chemical defenses in young than older tissues of D. ciliolata is the opposite of the pattern observed in coenocytic seaweeds and most vascular terrestrial and marine plants, all of which have translocation systems for moving materials among plant portions. Unlike these other plants, which preferentially allocate chemical defenses to young tissues, D. ciliolata cannot readily translocate secondary metabolites. The growth-differentiation balance hypothesis suggests that actively dividing and expanding cells are less able to produce secondary metabolites. This hypothesis may help explain why older tissues are better defended than young, rapidly growing apices. [ABSTRACT FROM AUTHOR]

Schistosomiasis is a parasitic disease that affects more than 250 million people. The treatment is limited to praziquantel and the control of the intermediate host with the highly toxic molluscicidal niclosamide. Marine algae are a poorly explored and promising alternative that can provide lead compounds, and the use of multivariate analysis could contribute to quicker discovery. As part of our search for new natural compounds with which to control schistosomiasis, we screened 45 crude extracts obtained from 37 Brazilian seaweed species for their molluscicidal activity against Biomphalaria glabrata embryos and schistosomicidal activities against Schistosoma mansoni. Two sets of extracts were taxonomically grouped for metabolomic analysis. The extracts were analyzed by GC–MS, and the data were subjected to Pattern Hunter and Pearson correlation tests. Overall, 22 species (60%) showed activity in at least one of the two models. Multivariate analysis pointed towards 3 hits against B. glabrata veliger embryos in the Laurencia/Laurenciella set, 5 hits against B. glabrata blastula embryos, and 31 against S. mansoni in the Ochrophyta set. Preliminary annotations suggested some compounds such as triquinane alcohols, prenylated guaianes, dichotomanes, and xenianes. Despite the putative identification, this work presents potential candidates and can guide future isolation and identification. [ABSTRACT FROM AUTHOR]

Species of the brown algae of the genus Dictyota are rich sources of bioactive secondary metabolites with diverse structural features. Excellent progress has been made in the discovery of diterpenes possessing broad chemical defensive activities from this genus. Most of these diterpenes exhibit significant biological activities, such as antiviral, cytotoxic and chemical defensive activities. In the present review, we summarized diterpenes isolated from the brown algae of the genus. [ABSTRACT FROM AUTHOR]