Fungia Scutaria Research Articles

Using coral skeletons for monitoring of heavy metals pollution in the Red Sea Coast, Egypt

The present work is the first study to specifically highlight a correlation between two different methods to monitor environmental pollution using hard corals as biomonitors. The first method involved comparing the concentrations of heavy metals in modern coral skeletons in both coasts of the Hurghada and Ras Mohamed nature reserve sites, whereas the second method involved comparing these concentrations in living coral species and the same Pleistocene ones. The results showed a similarity between the two monitoring methods. These results showed that the modern corals on the Hurghada site were enriched in all heavy metals in comparison with Ras Mohamed especially for Cu, Zn, Ni, and Co. The concentrations of these metals were higher than those in coasts of Red Sea (Saudi Arabia), Gulf of Aqaba (Jordan), Gulf of Mannar (India), Panama, Central America, and Australia. Furthermore, Hurghada coral skeletons suffered from higher concentrations of Cu, Pb, Cd, and Co than those in the earth’s carbonate rocks. These elements may enter Hurghada’s marine ecosystem by anthropogenic impacts as contamination from antifouling paint and oil spill from vessels. On the other hand, the Ras Mohamed site seems to be relatively unpolluted, except by Pb presumed to be due to oil spills from boat engines involved in extensive diving activities. The present work suggests that some coral species can be used as pollution biomonitoring as Stylophora pistillata for Cu and Co, Fungia scutaria for Zn and Cd, Pocillopora verrucosa for Pb, and Porites solida for Fe, Cu, and Ni. The microstructure and microarchitecture of the studied species play the essential role in the pollutant uptake, where the large reactive surface area and the amounts of intercrystalline porosity in coral skeletons are directly proportional to their amount of metal content. In spite of the mentioned results, the growth abnormality is not distinguished for the polluted recent species.

Implication of the host TGFβ pathway in the onset of symbiosis between larvae of the coral Fungia scutaria and the dinoflagellate Symbiodinium sp. (clade C1f)

Dinoflagellate–cnidarian associations form both the trophic and structural foundation of coral-reef ecosystems. Previous studies have highlighted the role of host innate immunity in regulation of these partnerships. This study reveals the presence of a transforming growth factor beta (TGFβ) in the coral Fungia scutaria that clusters with TGFβ sensu stricto (ss) from other animals. In functional studies of F. scutaria larvae, we show that (1) TGFβ ss mRNA is expressed during early stages of development prior to the onset of symbiosis; (2) apparent interference of the TGFβ pathway impairs the onset of symbiosis; and (3) this effect is associated with an increase of cytotoxic nitric oxide secretion, an immune response. This work highlights the importance of the TGFβ pathway in early life-history stages of corals by suggesting that its inhibition impacts the onset of symbiosis.

Relative sensitivity of five Hawaiian coral species to high temperature under high-pCO2 conditions

Coral reef ecosystems are presently undergoing decline due to anthropogenic climate change. The chief detrimental factors are increased temperature and increased pCO2. The purpose of this study was to evaluate the effect of these two stressors operating independently and in unison on the biological response of common Hawaiian reef corals. Manipulative experiments were performed using five species (Porites compressa, Pocillopora damicornis, Fungia scutaria, Montipora capitata, and Leptastrea purpurea) in a continuous-flow mesocosm system under natural sunlight conditions. Corals were grown together as a community under treatments of high temperature (2 °C above normal maximum summer temperature), high pCO2 (twice present-day conditions), and with both factors acting in unison. Control corals were grown under present-day pCO2 and at normal summer temperatures. Leptastrea purpurea proved to be an extremely hardy coral. No change in calcification or mortality occurred under treatments of high temperature, high pCO2, or combined high temperature–high pCO2. The remaining four species showed reduced calcification in the high-temperature treatment. Two species (L. purpurea and M. capitata) showed no response to increased pCO2. Also, high pCO2 ameliorated the negative effect of high temperature on the calcification rates of P. damicornis. Mortality was driven primarily by high temperature, with a negative synergistic effect in P. compressa only in the high-pCO2–high-temperature treatment. Results support the observation that biological response to temperature and pCO2 elevation is highly species-specific, so generalizations based on response of a single species might not apply to a diverse and complex coral reef community.

Potential bleaching effects on coral reproduction

Bleaching profoundly impacts coral reproduction, often for years after an event. However, detailed reproductive characteristics of coral after bleaching have not been broadly described, especially as they relate to cryopreservation. Therefore, in the present study we measured several reproductive characteristics in coral in Kaneohe Bay, Hawaii, for two species, namely Fungia scutaria and Montipora capitata, during the bleaching period of 2014 and 2015. We examined spawning periods, egg morphometry, sperm concentration, fresh and cryopreserved sperm motility exposed to different concentrations of dimethyl sulfoxide, time of first cleavage, larval survival with fresh and cryopreserved spermatozoa, infection success and settlement success. Many of these reproductive parameters were reduced in 2015, especially sperm motility. Once the reduced-motility spermatozoa from 2015 post-bleach were cryopreserved, there was a steep decline in post-thaw viability and this would prevent any substantive further use of these samples in reproduction for conservation benefit. Worldwide, as bleaching events become more frequent, the ability to bank and conserve coral ex situ may be significantly reduced. Thus, it is imperative that while genetic diversity is still high in these populations, intensive efforts are made to bank coral species during non-bleaching periods.

De Novo Assembly and Characterization of Four Anthozoan (Phylum Cnidaria) Transcriptomes.

Many nonmodel species exemplify important biological questions but lack the sequence resources required to study the genes and genomic regions underlying traits of interest. Reef-building corals are famously sensitive to rising seawater temperatures, motivating ongoing research into their stress responses and long-term prospects in a changing climate. A comprehensive understanding of these processes will require extending beyond the sequenced coral genome (Acropora digitifera) to encompass diverse coral species and related anthozoans. Toward that end, we have assembled and annotated reference transcriptomes to develop catalogs of gene sequences for three scleractinian corals (Fungia scutaria, Montastraea cavernosa, Seriatopora hystrix) and a temperate anemone (Anthopleura elegantissima). High-throughput sequencing of cDNA libraries produced ∼20–30 million reads per sample, and de novo assembly of these reads produced ∼75,000–110,000 transcripts from each sample with size distributions (mean ∼1.4 kb, N50 ∼2 kb), comparable to the distribution of gene models from the coral genome (mean ∼1.7 kb, N50 ∼2.2 kb). Each assembly includes matches for more than half the gene models from A. digitifera (54–67%) and many reasonably complete transcripts (∼5300–6700) spanning nearly the entire gene (ortholog hit ratios ≥0.75). The catalogs of gene sequences developed in this study made it possible to identify hundreds to thousands of orthologs across diverse scleractinian species and related taxa. We used these sequences for phylogenetic inference, recovering known relationships and demonstrating superior performance over phylogenetic trees constructed using single mitochondrial loci. The resources developed in this study provide gene sequences and genetic markers for several anthozoan species. To enhance the utility of these resources for the research community, we developed searchable databases enabling researchers to rapidly recover sequences for genes of interest. Our analysis of de novo assembly quality highlights metrics that we expect will be useful for evaluating the relative quality of other de novo transcriptome assemblies. The identification of orthologous sequences and phylogenetic reconstruction demonstrates the feasibility of these methods for clarifying the substantial uncertainties in the existing scleractinian phylogeny.

Seasonal Preservation Success of the Marine Dinoflagellate Coral Symbiont, Symbiodinium sp.

Coral reefs are some of the most diverse and productive ecosystems on the planet, but are threatened by global and local stressors, mandating the need for incorporating ex situ conservation practices. One approach that is highly protective is the development of genome resource banks that preserve the species and its genetic diversity. A critical component of the reef are the endosymbiotic algae, Symbiodinium sp., living within most coral that transfer energy-rich sugars to their hosts. Although Symbiodinium are maintained alive in culture collections around the world, the cryopreservation of these algae to prevent loss and genetic drift is not well-defined. This study examined the quantum yield physiology and freezing protocols that resulted in survival of Symbiodinium at 24 h post-thawing. Only the ultra-rapid procedure called vitrification resulted in success whereas conventional slow freezing protocols did not. We determined that success also depended on using a thin film of agar with embedded Symbiodinium on Cryotops, a process that yielded a post-thaw viability of >50% in extracted and vitrified Symbiodinium from Fungia scutaria, Pocillopora damicornis and Porites compressa. Additionally, there also was a seasonal influence on vitrification success as the best post-thaw survival of F. scutaria occurred in winter and spring compared to summer and fall (P < 0.05). These findings lay the foundation for developing a viable genome resource bank for the world’s Symbiodinium that, in turn, will not only protect this critical element of coral functionality but serve as a resource for understanding the complexities of symbiosis, support selective breeding experiments to develop more thermally resilient strains of coral, and provide a ‘gold-standard’ genomics collection, allowing for full genomic sequencing of unique Symbiodinium strains.

Trehalose is a chemical attractant in the establishment of coral symbiosis.

Coral reefs have evolved with a crucial symbiosis between photosynthetic dinoflagellates (genus Symbiodinium) and their cnidarian hosts (Scleractinians). Most coral larvae take up Symbiodinium from their environment; however, the earliest steps in this process have been elusive. Here we demonstrate that the disaccharide trehalose may be an important signal from the symbiont to potential larval hosts. Symbiodinium freshly isolated from Fungia scutaria corals constantly released trehalose (but not sucrose, maltose or glucose) into seawater, and released glycerol only in the presence of coral tissue. Spawning Fungia adults increased symbiont number in their immediate area by excreting pellets of Symbiodinium, and when these naturally discharged Symbiodinium were cultured, they also released trehalose. In Y-maze experiments, coral larvae demonstrated chemoattractant and feeding behaviors only towards a chamber with trehalose or glycerol. Concomitantly, coral larvae and adult tissue, but not symbionts, had significant trehalase enzymatic activities, suggesting the capacity to utilize trehalose. Trehalase activity was developmentally regulated in F. scutaria larvae, rising as the time for symbiont uptake occurs. Consistent with the enzymatic assays, gene finding demonstrated the presence of a trehalase enzyme in the genome of a related coral, Acropora digitifera, and a likely trehalase in the transcriptome of F. scutaria. Taken together, these data suggest that adult F. scutaria seed the reef with Symbiodinium during spawning and the exuded Symbiodinium release trehalose into the environment, which acts as a chemoattractant for F. scutaria larvae and as an initiator of feeding behavior- the first stages toward establishing the coral-Symbiodinium relationship. Because trehalose is a fixed carbon compound, this cue would accurately demonstrate to the cnidarian larvae the photosynthetic ability of the potential symbiont in the ambient environment. To our knowledge, this is the first report of a chemical cue attracting the motile coral larvae to the symbiont.

068 Challenges of creating a frozen repository for coral

Over the next 30 to 40 years, rising ocean temperatures and increased ocean acidification have the potential to overpower the vast majority of current in situ coral conservation efforts, resulting in severe loss of reef biodiversity. If this occurs, ex situ coral conservation incorporating cryopreservation may provide an important means for successful reef diversification. To build new tools for the continued protection and propagation of coral, an international group of coral and cryopreservation scientists known as the Reef Recovery Initiative joined forces. The outcome was the creation of the first frozen bank for Australian, Caribbean and Hawaiian coral, containing 8 important reef-building species including, Acropora tenuis, Acropora millepora, Acropora loripes, Platygyra daedalea, Platygyra lamolina, Fungia scutaria, Acropora palmata and Acropora cervicornis. Most species of coral are hermaphrodites and reproduce sexually by producing lipid-rich egg/sperm bundles. Generally, self-fertilization is low. A simple, uniform freezing method (10% Me 2 SO in seawater with a freezing rate of 20°C/min) was devised to cryopreserve the sperm of all these species. Coral reproduction is driven by access to sunlight, which powers the intracellular algae to produce complex sugars for the coral. In turn, the coral use these sugars to build lipids needed for the germplasm. Even though we found a unified method for sperm cryopreservation in coral there were physiological challenges. For example, sperm production across the complex web of polyps in single genetic individuals varied. Specifically, in 2011 egg/sperm bundles with more eggs produced more motile sperm. This variation may have been caused by polyp age, prior damage, access to sunlight or a combination of factors. An additional challenge was a ‘night-of-preservation’ effect whereby some nights the sperm preservation from pooled colonies produced widely differing post-thaw motility, as well as cryopreservation and fertilization success. Finally, when this simple sperm cryopreservation method was used on the Hawaiian acroporid, Montipora captitata, it consistently produced low post-thaw motility and no fertilization success. This species was found to have a toxin in the adult tissue that it transferred to the eggs and possibly the sperm prior to reproduction. Therefore, the release of this toxin from slightly damaged sperm cells may have impacted these post-thaw results, and may ultimately inhibit the successful cryopreservation of this species. Finally, coral larvae have not been successfully cryopreserved because of their exquisite chilling sensitivity. Nevertheless, pluripotent 8-cell embryos were successfully dissociated, frozen and thawed with 50 to 90% intact cells post-thaw in all species tested. Frozen and thawed coral sperm can now be used to create new coral, as they develop, settle and take up their intracellular algae. In the near future, we may have a blueprint to move our work from the laboratory to the reefs to develop collaborative, practical conservation management tools to secure reef biodiversity. Source of funding: This work was supported by the Roddenberry Foundation, Matthew Frank Foundation, Taronga Conservation Society Australia, Australian Institute of Marine Science, Anela Kolohe Foundation, Hawaii Institute of Marine Biology and the Smithsonian Institution. Conflict of interest: None declared. hagedornm@si.edu

Preserving and Using Germplasm and Dissociated Embryonic Cells for Conserving Caribbean and Pacific Coral

Coral reefs are experiencing unprecedented degradation due to human activities, and protecting specific reef habitats may not stop this decline, because the most serious threats are global (i.e., climate change), not local. However, ex situ preservation practices can provide safeguards for coral reef conservation. Specifically, modern advances in cryobiology and genome banking could secure existing species and genetic diversity until genotypes can be introduced into rehabilitated habitats. We assessed the feasibility of recovering viable sperm and embryonic cells post-thaw from two coral species, Acropora palmata and Fungia scutaria that have diffferent evolutionary histories, ecological niches and reproductive strategies. In vitro fertilization (IVF) of conspecific eggs using fresh (control) spermatozoa revealed high levels of fertilization (>90% in A. palmata; >84% in F. scutaria; P>0.05) that were unaffected by tested sperm concentrations. A solution of 10% dimethyl sulfoxide (DMSO) at cooling rates of 20 to 30°C/min most successfully cryopreserved both A. palmata and F. scutaria spermatozoa and allowed producing developing larvae in vitro. IVF success under these conditions was 65% in A. palmata and 53% in F. scutaria on particular nights; however, on subsequent nights, the same process resulted in little or no IVF success. Thus, the window for optimal freezing of high quality spermatozoa was short (∼5 h for one night each spawning cycle). Additionally, cryopreserved F. scutaria embryonic cells had∼50% post-thaw viability as measured by intact membranes. Thus, despite some differences between species, coral spermatozoa and embryonic cells are viable after low temperature (−196°C) storage, preservation and thawing. Based on these results, we have begun systematically banking coral spermatozoa and embryonic cells on a large-scale as a support approach for preserving existing bio- and genetic diversity found in reef systems.

Elevated temperature impairs onset of symbiosis and reduces survivorship in larvae of the Hawaiian coral, Fungia scutaria

Many corals obtain their obligate intracellular dinoflagellate symbionts from the environment as larvae or juveniles. The process of symbiont acquisition remains largely unexplored, especially under stress. This study addressed both the ability of Fungia scutaria (Lamarck 1801) larvae to establish symbiosis with Symbiodinium sp. C1f while exposed to elevated temperature and the survi- vorship of aposymbiotic and newly symbiotic larvae under these conditions. Larvae were exposed to 27, 29, or 31C for 1 h prior to infection, throughout a 3-h infection period, and up to 72 h following infection. Exposure to elevated temperatures impaired the ability of coral larvae to estab- lish symbiosis and reduced larval survivorship. At 31C, the presence of symbionts further reduced larval survi- vorship. As sea surface temperatures rise, coral larvae exposed to elevated temperatures during symbiosis onset will likely be negatively impacted, which in turn could affect the establishment of future generations of corals.

Coral larvae exhibit few measurable transcriptional changes during the onset of coral-dinoflagellate endosymbiosis

The cellular mechanisms controlling the successful establishment of a stable mutualism between cnidarians and their dinoflagellate partners are largely unknown. The planula larva of the solitary Hawaiian scleractinian coral Fungia scutaria and its dinoflagellate symbiont Symbiodinium sp. type C1f represents an ideal model for studying the onset of cnidarian-dinoflagellate endosymbiosis due to the predictable availability of gametes, the ability to raise non-symbiotic larvae and establish the symbiosis experimentally, and the ability to precisely quantify infection success. The goal of this study was to identify genes differentially expressed in F. scutaria larvae during the initiation of endosymbiosis with Symbiodinium sp. C1f. Newly symbiotic larvae were compared to non-symbiotic larvae using a custom cDNA microarray. The 5184-feature array was constructed with cDNA libraries from newly symbiotic and non-symbiotic F. scutaria larvae, including 3072 features (60%) that were enriched for either state by subtractive hybridization. Our analyses revealed very few changes in the F. scutaria transcriptome as a result of infection with Symbiodinium sp. C1f, similar to other studies focused on the early stages of this symbiotic interaction. We suggest that these results may be due, in part, to an inability to detect the transcriptional signal from the small percentage of infected cells compared to uninfected cells. We discuss several other potential explanations for this result, including suggesting that certain types of Symbiodinium sp. may have evolved mechanisms to suppress or circumvent cnidarian host responses to infection.

Analysis of Internal Osmolality in Developing Coral Larvae,Fungia scutaria

Coral species throughout the world are facing severe local and global environmental pressures. Because of the pressing conservation need, we are studying the reproduction, physiology, and cryobiology of coral larvae with the future goal of cryopreserving and maintaining these organisms in a genome resource bank. Effective cryopreservation involves several steps, including the loading and unloading of cells with cryoprotectant and the avoidance of osmotic shock. In this study, during the time course of coral larvae development of the mushroom coral Fungia scutaria, we examined several physiologic factors, including internal osmolality, percent osmotically active water, formation of mucus cells, and intracellular organic osmolytes. The osmotically inactive components of the cell, V(b), declined 33% during development from the oocyte to day 5. In contrast, measurements of the internal osmolality of coral larvae indicated that the internal osmolality was increasing from day 1 to day 5, probably as a result of the development of mucus cells that bind ions. Because of this, we conclude that coral larvae are osmoconformers with an internal osmolality of about 1,000 mOsm. Glycine betaine, comprising more than 90% of the organic osmolytes, was found to be the major organic osmolyte in the larvae. Glycerol was found in only small quantities in larvae that had been infected with zooxanthellae, suggesting that this solute did not play a significant role in the osmotic balance of this larval coral. We were interested in changes in cellular characteristics and osmolytes that might suggest solutes to test as cryoprotectants in order to assist in the successful cryopreservation of the larvae. More importantly, these data begin to reveal the basic physiological events that underlie the move from autonomous living to symbiosis.

Development of microsatellite markers from four Hawaiian corals: Acropora cytherea, Fungia scutaria, Montipora capitata and Porites lobata

Comprehensive population genetic studies of coral communities are comparatively rare, because of the scarcity of population genetic markers. The Hawaiian archipelago offers a unique perspective into understanding the population genetic structuring of this ecologically important group of organisms. Here we report the development of microsatellite marker libraries from holobiont extracts of four corals: Acropora cytherea (n = 50), Fungia scutaria (n = 118), Montipora capitata (n = 140) and Porites lobata (n = 149). Blast searches indicate that these libraries contain microsatellites from both the coral host and Symbiodinium endosymbionts from each coral. In addition, we also present redesigned primers for the nuclear coding region (atpsβ) for use in M. capitata. We report testing and optimization for seven of these microsatellites from A. cytherea, and eight microsatellites and the atpsβ locus from M. capitata. Using 25 individuals per species collected from each French Frigate Shoals (FF) and Johnston Atoll (JO), the number of alleles per locus ranged from 2 to 9. Expected heterozygosities ranged from 0.38 to 0.85 and 0.08 to 0.87 for A. cytherea and M. capitata, respectively. We expect that these libraries will be a valuable resource and provide additional useful microsatellite markers for both the coral host and zooxanthellae.

Physiology and cryosensitivity of coral endosymbiotic algae ( Symbiodinium)

Coral throughout the world are under threat. To save coral via cryopreservation methods, the Symbiodinium algae that live within many coral cells must also be considered. Coral juvenile must often take up these important cells from their surrounding water and when adult coral bleach, they lose their endosymbiotic algae and will die if they are not regained. The focus of this paper was to understand some of the cryo-physiology of the endosymbiotic algae, Symbiodinium, living within three species of Hawaiian coral, Fungia scutaria, Porites compressa and Pocillopora damicornis in Kaneohe Bay, Hawaii. Although cryopreservation of algae is common, the successful cryopreservation of these important coral endosymbionts is not common, and these species are often maintained in live serial cultures within stock centers worldwide. Freshly-extracted Symbiodinium were exposed to cryobiologically appropriate physiological stresses and their viability assessed with a Pulse Amplitude Fluorometer. Stresses included sensitivity to chilling temperatures, osmotic stress, and toxic effects of various concentrations and types of cryoprotectants (i.e., dimethyl sulfoxide, propylene glycol, glycerol and methanol). To determine the water and cryoprotectant permeabilities of Symbiodinium, uptake of radio-labeled glycerol and heavy water (D 2O) were measured. The three different Symbiodinium subtypes studied demonstrated remarkable similarities in their morphology, sensitivity to cryoprotectants and permeability characteristics; however, they differed greatly in their sensitivity to hypo- and hyposmotic challenges and sensitivity to chilling, suggesting that standard slow freezing cryopreservation may not work well for all Symbiodinium. An appendix describes our H 2O:D 2O water exchange experiments and compares the diffusionally determined permeability with the two parameter model osmotic permeability.

Mycosporine-like amino acids in six scleractinian coral species

Mycosporine-like amino acids (MAAs) were studied in stony coral species (Fungi- idae) along the Eastern coast of the Red Sea. Six species - Fungia scutaria, F. danai, F. corona, F. repanda, Ctenactis echinata and Lithophyllor lobata - were examined for MAAs at water depths of 5, 10, 15 and 20 m. Protein and chlorophyll were also determined and showed higher contents in winter than in summer. Generally, the total content of MAAs in summer was found to be approximately three times greater than in winter. Overall, concentrations of MAAs were greatest at a depth of 5 m. Porphyra-334 was the most abundant MAA in F. scutaria and F. danai, whereas asterina-330 was either not detectable (e.g. L. lobata) or present in low concentrations (e.g. F. danai, F. repanda and C. echinata). Shinorine was not detected in F. danai or L. lobata. Both C. echinata and L. lobata had the lowest concentrations of MAAs, presumably because of their large calcareous skeletons. The variation in MAA concentrations among seasons and water depths is probably due to a number of factors, including the intensity of solar radiation, turbidity and phylogenetic variation.

Apoptosis as a post‐phagocytic winnowing mechanism in a coral–dinoflagellate mutualism

This study was aimed at detecting apoptosis as a post-phagocytic mechanism of symbiont selection during the onset of symbiosis in larvae of the scleractinian coral Fungia scutaria. Larvae were infected with one of three Symbiodinium types: freshly isolated homologous ITS-type C1f from adult F. scutaria, heterologous C31 from adult Montipora capitata, known to be unable to successfully colonize F. scutaria larvae, and type B1 from the symbiotic sea anemone Aiptasia spp. Apoptosis was detected by the activation of caspases, enzymes specific to apoptosis. Caspase activity was measured in situ by cleavage of a specific fluorophore and detection with confocal microscopy. At 6 h post infection, there was a significant increase in caspase activation in gastrodermal cells in C31-infected larvae, compared with larvae infected with C1f or B1 types. Compared with control larvae infected with C31, which had decreased infection rates present by 24 h post infection, when C31-infected larvae were incubated with a broad-scale caspase inhibitor, the per cent of larvae infected with C31 did not significantly decrease over time. This indicates that the reduction in infection success observed in untreated C31-infected larvae can be rescued with inhibition of caspases and apoptosis. This suggests the presence of a post-phagocytic recognition mechanism. Larvae infected with freshly isolated B1 retained infection success over time compared with C31-infected larvae, suggesting that there is host discrimination between heterologous algae. Initiation of this post-phagocytic response may occur more readily with a highly specific heterologous symbiont type such as C31, compared with a generalist heterologous type such as clade B1.

Photosynthesis and respiration of hermatypic zooxanthellate Red Sea corals from 5-75-m depth

Hermatypic zooxanthellate corals depend on light for photosynthesis. As such, they will not grow at depths deeper than 100 m. Submersible respirometers were used to monitor changes in oxygen concentration for five corals species, Favia favus, Fungia scutaria, Lobophyllia sp., Mycedium sp., and Stylophora pistillata. Variations in chlorophyll concentrations, zooxanthellae cell densities, photosynthesis, and respiration rates were detected in these coral species. Two clusters emerged when correlated with deep water, indicating different populations. The first group was restricted to the surface-40 m depth and the second to the 40-75-m depth. Light intensity for saturating photosynthesis Ek was less than 320 μmol q m-2 s-1 for all species and decreased with depth for most of them.

Phylogenetic diversity of bacteria associated with the mucus of Red Sea corals

Coral reefs are the most biodiverse and biologically productive of all marine ecosystems. Corals harbor diverse and abundant prokaryotic communities. However, little is known about the diversity of coral-associated bacterial communities. Mucus is a characteristic product of all corals, forming a coating over their polyps. The coral mucus is a rich substrate for microorganisms. Mucus was collected with a procedure using sterile cotton swabs that minimized contamination of the coral mucus by surrounding seawater. We used molecular techniques to characterize and compare the bacterial assemblages associated with the mucus of the solitary coral Fungia scutaria and the massive coral Platygyra lamellina from the Gulf of Eilat, northern Red Sea. The bacterial communities of the corals F. scutaria and P. lamellina were found to be diverse, with representatives within the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria and Epsilonproteobacteria, as well as the Actinobacteria, Cytophaga-Flavobacter/Flexibacter-Bacteroides group, Firmicutes, Planctomyces, and several unclassified bacteria. However, the total bacterial assemblage of these two corals was different. In contrast to the bacterial communities of corals analyzed in previous studies by culture-based and culture-independent approaches, we found that the bacterial clone libraries of the coral species included a substantial proportion of Actinobacteria. The current study further supports the finding that bacterial communities of coral mucus are diverse.

Proteomic and transcriptional analyses of coral larvae newly engaged in symbiosis with dinoflagellates

Many marine cnidarians, such as stony corals, engage in intracellular symbiosis with dinoflagellates, forming the trophic and structural foundation of the coral reef ecosystem. Very little is known about the cellular and molecular mechanisms that are at work in these associations. In this study, we examined changes in both the soluble proteome and the transcriptome of larvae of the Hawaiian solitary coral Fungia scutaria during the onset of symbiosis with Symbiodinium sp. We conducted a comparative host coral proteome analysis using 2-dimensional gel electrophoresis, as well as a comparative host coral transcriptome analysis using a cDNA subtracted library and real-time quantitative PCR. Age-related changes in the larval protein profiles were detected, however virtually no symbiosis-related changes in the protein profiles were evident. Symbiosis-related differences in gene expression were found using a subtracted library, although the differences were very subtle and almost undetectable using real-time quantitative PCR.

Two Atypical Carbonic Anhydrase Homologs From the Planula Larva of the Scleractinian CoralFungia scutaria

In cnidarians, the enzyme carbonic anhydrase (CA) is important to inorganic carbon (Ci) flux in processes including calcification and dinoflagellate symbiont photosynthesis. Although CA is known to function in Ci delivery to symbionts in adults with mature symbioses, it is not known when CA becomes active in this capacity during the onset of symbiosis in developing hosts. We identified two CA cDNA sequences from the planula larvae of the Hawaiian scleractinian coral Fungia scutaria. Expression of these larval CAs did not differ between infected and uninfected larvae or vary over the course of infection. Bioinformatic analyses of the two homologs showed that the sequences are unusually short and are missing some residues that support active site structure in other CAs. This is the first description of a short form of CA. Phylogenetic analyses of the larval CAs grouped them with membrane-bound homologs from vertebrates. Studies in other calcifying cnidarians have identified membrane-associated CAs as functioning in calcification, and therefore the two larval CAs could play a role in the onset of calcification during metamorphosis. A longer CA isoform was amplified from adult F. scutaria cDNA but not from larvae, suggesting that the longer form is not expressed in larvae. The longer form grouped with cytosolic CAs including a symbiotic anemone homolog implicated in Ci delivery to dinoflagellate symbionts. The apparent absence of this "symbiosis" CA in larvae suggests that the Ci supply mechanism is not active during the initial onset of the association.