Seriatopora Hystrix Research Articles

Ultraviolet‐B radiation stimulates shikimate pathway‐dependent accumulation of mycosporine‐like amino acids in the coral Stylophora pistillata despite decreases in its population of symbiotic dinoflagellates

Colonies of Stylophora pistillata maintained for four years in indoor aquaria in the near absence of ultraviolet radiation (UVR) contained only small amounts (<5 nmol mg−1 protein) of 10 identified mycosporine‐like amino acids (MAAs, which act as UV sunscreens), the largest number reported in any organism. The concentrations of most MAAs increased linearly or exponentially when colonies were exposed to ultraviolet‐A (UVA) and ultraviolet‐B (UVB) for 8 h d−1 in the presence of photosynthetically active radiation (PAR). Total MAA concentration reached 174 nmol mg−1 protein after 30 d, with palythine and mycosporine−2 glycine constituting more than half of the final total. UVB specifically stimulated MAA accumulation: after 15 d, MAA levels in colonies exposed to PAR alone and to PAR and UVA did not differ (7 and 5 nmol MAA mg−1 protein, respectively), while those in colonies exposed to PAR and UVA + UVB were significantly higher (28 nmol mg−1 protein). Glyphosate, an inhibitor of the shikimate pathway, eliminated or reduced the UV‐induced accumulation of most MAAs during 7 d of exposure, providing the first experimental evidence of their synthesis via this pathway in a coral symbiosis. Densities of zooxanthellae in colonies of S. pistillata, Acropora sp., and Seriatopora hystrix exposed to UVR for 15 d were only one‐third of those in control colonies unexposed to UVR. This net decrease in the number of zooxanthellae in the corals (bleaching) occurred despite UV stimulated increases in algal cytokinesis and in the host cell‐specific density of zooxanthellae in hospite, increases that apparently destabilized the symbiosis and caused expulsion of the zooxanthellae.

Seasonality and lunar periodicity in the reproduction of Pocilloporid corals

Reproductive seasonality and lunar periodicity of planula release were investigated for the three brooding coralsPocillopora damicornis, Seriatopora hystrix, andStylophora pistillata at Heron Island in the southern Great Barrier Reef. Branch fragments collected from undisturbed colonies in the field were used to determine when planulae were present for all three species, and direct observations of planula release were made on colonies ofPocillopora kept in aquaria. All three species displayed marked seasonal variation in reproductive output, with nearly all reproductive activity occurring over the summer months.Pocillopora exhibited distinct lunar periodicity in planulation, with planula release occurring around three quarter moon, and no planulae being present in samples collected between new and full moons.Seriatopora also displayed lunar periodicity of planula release, although it was not as distinct as forPocillopora, whileStylophora did not show any lunar periodicity.

Isolation and Partial Characterization of the Pink and Blue Pigments of Pocilloporid and Acroporid Corals.

The compounds responsible for the pink and blue colors of two families of hermatypic corals (Pocilloporidae, Acroporidae) from the southern Great Barrier Reef were isolated and biochemically characterized. Isolation of the pink pigment from Pocillopora damicornis (named pocilloporin, {lambda}max = 560 nm, 390 nm) revealed that it was a hydrophilic protein dimer with a native molecular weight of approximately 54 kD and subunits of 28 kD. The subunits are not linked by disulfide bonds. Attempts to dissociate the chromophore from the protein proved unsuccessful. Denaturing the protein with heat (60{deg}C) or 5% sodium dodecyl sulfate (SDS) removed the 560-nm absorbance peak without introducing a detectable bathochromic shift. In acetone, ethanol, ether, and chloroform, the pigment precipitates out of solution, leaving a colorless supernatant. These properties suggest that the protein and chromophore are covalently linked. Ion analysis revealed that the pigment does not have metal ions chelated to it. Coral pigments were also isolated from pink morphs of other pocilloporids, Seriatopora hystrix ({lambda}max = 560 nm) and Stylophora pistillata ({lambda}max = 560 nm); and from bluish regions of the acroporids, Acropora formosa (blue; {lambda}max = 590 nm) and Acropora digitifera (purple; {lambda}max = 580 nm). With the exception of A. formosa, all the corals examined had pigments with the same native (54 kD) and subunit (28 kD) molecular weights as those of P. damicornis. A. formosa pigment has a native molecular weight of about 82.6 kD and three subunits of 28 kD. The pigments isolated from each of these coral species have properties similar to those described for P. damicornis. Isolation and biochemical purification of the pigment enabled the exploration of the function of the pink pigment. Three possibilities were eliminated. The compound does not act as (i) a photoprotectant for shielding the photosynthetic pigments of symbiotic zooxanthellae against excessive irradiances, (ii) a fluorescent coupling agent for amplifying the levels of photosynthetically active radiation available for resident zooxanthellae, or (iii) a UV-screen against the high UV levels of shallow tropical marine environments.

EVIDENCE FOR RESTRICTED GENE FLOW IN THE VIVIPAROUS CORAL SERIATOPORA HYSTRIX ON AUSTRALIA'S GREAT BARRIER REEF.

Viviparous, branching corals such as Seriatopora hystrix are expected to generate most recruits through asexual reproduction (fission or fragmentation) but are expected to use sexual reproduction to produce widely dispersed colonists. In this study, allozyme electrophoresis was used to test for variation in the relative contributions of sexual and asexual reproduction to recruitment and to assess the apparent scale of larval dispersal (gene flow) in the central Great Barrier Reef. Fifty-seven collections (within ≤ 25 m2 ) of fragments from sets of approximately 40 colonies were made (where possible) within each of five habitats on each of 12 reefs. These reefs, within the central region of the Great Barrier Reef, were separated by up to 90 km and included one inner-shelf continental island and groups of seven midshelf reefs and four outer-shelf reefs. Most collections contained a high level of multilocus genotypic diversity and hence showed little evidence of recruitment through fragmentation, although the majority of collections displayed large and consistent deficits of heterozygotes. Allele frequencies varied greatly among collections (FST = 0.43), and this variation was sufficient to explain two-thirds of observed deficiencies of heterozygotes via a Wahlund effect. A hierarchical assessment of FST values revealed that 45% of allelic variation occurred among reefs (FST = 0.20), and only 16% of variation within reefs was explained by variation among five major habitat types (FST = 0.05). A relatively small component of the total variation among samples was attributable to across-shelf variation among the groups of middle- and outer-shelf reefs (FST = 0.03); however, the outer-shelf reefs form a single UPGMA cluster separate from all but 4 of the other 43 collections. These data imply that widespread dispersal does occur but that the direction or magnitude of gene flow may be influenced by the along-shelf movement of major ocean currents and weather-dependent currents on or near reefs. Each reef, therefore, forms a partially isolated and highly subdivided population.

Evidence for Restricted Gene Flow in the Viviparous Coral Seriatopora hystrix on Australia's Great Barrier Reef

Evidence for Restricted Gene Flow in the Viviparous Coral Seriatopora hystrix on Australia's Great Barrier Reef

The effect of sudden changes in temperature, light and salinity on the population density and export of zooxanthellae from the reef corals Stylophora pistillata Esper and Seriatopora hystrix Dana

Bleaching (loss of pigmentation by corals) is a widespread phenomenon in coral-reef ecosystems. Despite this, the underlying causes of some forms of bleaching are poorly understood. This study explores the conditions that induce bleaching in two species of reef coral-zooxanthellae associations from Lizard Island, Great Barrier Reef, Australia. Naturally bleached Stylophora pistillata Esper and Seriatopora hystrix Dana, collected from the edge of Lizard Island lagoon, had the same amount of Chl a · zooxanthellae −1, yet had reduced population densities of zooxanthellae when compared to normal-looking colonies. In this case, the lack of pigment in the bleached corals was explained by low numbers of zooxanthellae and not by pale zooxanthellae. This is contrary to results obtained by some other workers and suggests that closer inspection of the underlying reasons for the pale color of bleached corals is warranted. In laboratory experiments, sudden exposures to full sunlight induced the bleaching of S. pistillata previously grown at 25% sunlight. The pale color of colonies exposed to full sunlight was explained by the low pigment content of the zooxanthellae rather than by low population densities of zooxanthellae. In addition, the specific expulsion rate of zooxanthellae from S. Pistillata and S. hystrix was not influenced by sudden increases in solar irradiance. Sudden exposures to reduced salinities (30%.) did not affect S. Pistillata or S. hystrix in this study. Both species bleached rapidly, however, when exposed to water temperatures of > 30 °C. Bleached corals in this case had reduced population densities of zooxanthellae despite normal zooxanthella pigment contents. The specific expulsion rate of zooxanthellae from both species of coral was very sensitive to temperature. 7-h exposures to 30 and 32 °C resulted in specific expulsion rates of > 1000 times that of controls. Specific expulsion rates remained high, even when corals were returned to control temperatures (27 °C). After high temperature stress, S. Pistillata and S. hystrix had high and sustained colony respiratory rates ( r c ), reduced colony photosynthetic rates ( p c net max ) and reduced P c g max : r c ratios. The O 2 metabolism of the S. pistillata and S. hystrix symbioses remained abnormal for up to 4 days after a 7-h exposure to 32 °C. Evidence suggestive of recovery was apparent 19 days later. By this time, the mean population density of zooxanthellae and p c g max : r c ratios of exposed fragments had returned to normal.

Isomolgus desmotes, New Genus, New Species (Lichomolgidae), a Gallicolous Poecilostome Copepod from the Scleractinian Coral Seriatopora hystrix Dana in Indonesia, with a Review of Gall-Inhabiting Crustaceans of Anthozoans

Isomolgus desmotes, New Genus, New Species (Lichomolgidae), a Gallicolous Poecilostome Copepod from the Scleractinian Coral Seriatopora hystrix Dana in Indonesia, with a Review of Gall-Inhabiting Crustaceans of Anthozoans

ISOMOLGUS DESMOTES, NEW GENUS, NEW SPECIES (LICHOMOLGIDAE), A GALLICOLOUS POECILOSTOME COPEPOD FROM THE SCLERACTINIAN CORAL SERIATOPORA HYSTRIX DANA IN INDONESIA, WITH A REVIEW OF GALL-INHABITING CRUSTACEANS OF ANTHOZOANS

ABSTRACT Isomolgus desmotes, new genus, new species, a lichomolgid copepod with a swollen prosome, is described from galls in Seriatopora hystrix Dana collected in Indonesia. This is the first report of a gallicolous poecilostome copepod from a scleractinian coral. The morphology and possible scenario for development of the gall are discussed, and a review of gall-inhabiting crustaceans of anthozoans is provided.

Nutrient uptake kinetics of freshly isolated zooxanthellae

Zooxanthellae of the species Gymnodinium (=Symbiodinium) microadriaticum freshly isolated from a variety of hosts (Zoanthus spp., Tridacna crocea, Seriatopora hystrix, Montastrea annularis, Porites furcata, and Stylophora pistillata) in the tropical Pacific Ocean and the Caribbean Sea exhibited saturation uptake kinetics when incubated in seawater enriched with nitrate, nitrite or ammonium. Half-saturation constants (Ks) for nitrate ranged from 0.23 to 3.14 μM, for nitrite from 0.23 to 7.15 μM, and for ammonium from 5.03 to 21.99 μM. Maximum specific uptake rates (Vmax) for ammonium (1.05 to 2.79 d-1) exceeded those for both nitrate (not detectable to 0.54 d-1) and nitrite (not detectable to 0.67 d-1). Light did not affect the uptake rate of any substrate tested, nor did the addition of ammonium in concentrations up to 20 μM reduce the rate of nitrate uptake at Vmax, but nitrite uptake was inhibited by the addition of nitrate to the medium. The inhibition of nitrite uptake by nitrate could not be described either as competitive or non-competitive. Although maximum specific uptake rates obtained for ammonium appear to exceed maximum potential specific growth rate in terms of nitrogen of the algae, the actual growth potential of the algae must be limited not only by nutrient concentrations to which they are exposed, but also by the percentage of assimilated nitrogen that they translocate to their host. Uptake rates obtained for isolated zooxanthellae in this study are similar to those obtained previously for intact coral-zooxanthellae symbioses. This evidence is consistent with the hypothesis that nutrient uptake by intact zooxanthellae-host symbioses occurs by diffusion down a concentration gradient created by localized substrate depletion by the zooxanthellae in host tissue.

Diurnal carbon-14 partitioning between zooxanthellae and the coral animal tissue of intact Seriatopora hystrix colonies

At various times throughout the light period of a day, freshly harvested Seriatopora hystrix colonies in seawater were labeled with H14CO 3 - for 20 min and then washed thoroughly with fresh seawater. The labeled colonies were left in fresh seawater, and at time intervals (some as long as 27h) samples were removed, separated into zooxanthellae and coral animal tissue, and the radioactivity in the two fractions determined. In 30 to 60 min after initiating the experiments, the zooxanthellae retained 75 to 82% of the total label. Zooxanthellae labeled early in a day lose label throughout the day and near sunset retain about 55% of the total label in the colony. Colonies labeled in the last 1 to 2 h of daylight retain 65 to 73% of the label in the zooxanthellae. At night the zooxanthellae retain almost all of their 14C-labeled materials regardless of the labeling hour of the previous day. A loss of carbon at night from the zooxanthellae occurred only when the colonies were labeled in the last 1 to 2 h of daylight; the loss was approximately 5% over the night period. The next day, after several hours of light, 14C-labeled material again moved from the zooxanthellae to the animal tissue. We conclude that in the intact coral as much as 45% of the newly fixed carbon moves from the zooxanthellae to the animal tissue each day, but that little net carbon movement between these two organisms occurs at night.

Effects of carbon dioxide concentration on coral photosynthesis

The effects of inorganic carbon concentrations on photosynthetic oxygen evolution of isolated zooxanthellae and coral tips from the hermatypic coral Seriatopora hystrix were measured in the laboratory using an oxygen electrode. Whole coral colonies of Stylophora pistillata were examined in situ, using a bioassay respirometer. Inorganic carbon concentrations above 2.3 mM, the ambient concentration of reef water, generally did not stimulate photosynthesis. These results indicate that inorganic carbon is not limiting to coral photosynthesis and that respiratory carbon dioxide production by the coral host probably has little effect on the photosynthetic rates of its symbiotic zooxanthellae.

Spatial and temporal patterns of recuruitment of juvenile coral reef fishes to coral habitats within ?One Tree Lagoon?, great barrier reef

Recruitment of juvenile fishes to coral grids, each comprising 4 colonies of 3 species of coral (Acropora formosa, Seriatopora hystrix and Pocillopora damicornis), was examined at 4 widely separated sites within the lagoon of “One Tree Reef” over two successive summers and intervening months (November 1976–January 1978). Recruitment was highly seasonal, with most recruitment occurring during summer. For many species, numbers settling differed greatly from year to year with total numbers (over all sites) differing as much as an order of magnitude between summers. Many fish species demonstrated marked preference among the three coral species as settling sites. The distribution of each of the 20 commonest species across the 4 lagoon sites differed significantly from a random pattern. Differences of an order of magnitude were common in the numbers of a given species recruited to different sites. Each site was preferred by at least one species. In each of 5 cases examined, the pattern of settlement of the species across the 4 sites changed significantly from one summer to the next. The distribution of recruits of a number of species corresponded to the distribution of adults, but for other species there was no correspondence. It is concluded that, at the spatial scale examined, patterns of recruitment of some taxa are consistently more variable than those of other taxa. The implications of spatial variability of recruitment for the distribution of adult fish is discussed and the importance of being able to discriminate such “natural” variability from other kinds of change is stressed.