Dissertations / Theses on the topic 'Stylophora'

Small non-coding RNAs such as microRNAs (miRNAs), small interfering RNAs (siRNAs) and Piwi-interacting RNAs (piRNAs) play a big role in regulating gene expression in cells. In my work, I focus primarily on miRNAs, which represses the expression of the mRNA targets post-transcriptionally. For Drosophila melanogaster, I predicted the tissue-specific expression of several miRNAs based on the expression levels of the predicted mRNA targets in those tissues. The computational predictions are then followed up by quantitative PCR validation of miRNA expression levels in dissected fly tissues. For Stylophora pistillata (a species of coral found in the Red Sea) and Symbiodinium sp. (a photosynthetic, symbiotic algae present in the coral cell), my collaborators and I strived to study the genome, transcriptome and proteome of both organisms. At present, there is another coral genome available — from Acropora digitifera — but the large evolutionary distance between both corals (about 240 million years apart) warrants in-depth study of our coral of interest. On the other hand, our Symbiodinium genome will be the first of its kind for any dinoflagellate. My role in the project was to investigate the small RNAome of both organisms via small RNAseq. As the presence of a thick cell wall in Symbiodinium sp. poses a unique challenge to RNA extraction, and compounded by the dearth of literature regarding RNA extraction from the dinoflagellate, we optimised a procedure that consistently produced high quality RNA for downstream sequencing. From our draft proteome, I showed that the RNA interference (RNAi) machinery is very likely to be present in both organisms. Based on our short RNAseq data, I predicted miRNAs in both organisms. Two of the predicted miRNAs in S. pistillata have been identified in other organisms, while all of the predicted miRNAs in Symbiodinium sp. were novel.

La formation d’un squelette de CaCO3 par les coraux Scléractiniaires est à la base de l’édification des récifs coralliens. Nombre de ces coraux constructeurs de récif vivent en symbiose avec des Dinoflagellés photosynthétiques. Ces deux processus reposent sur le transport et l’utilisation de carbone inorganique (Ci) provenant de l’eau de mer pour la photosynthèse, et du métabolisme animal pour la calcification. Cette thèse s’est intéressée à l’étude moléculaire et physiologique des mécanismes, permettant l’utilisation de ce carbone inorganique.Malgré l’importance des transports de HCO3-, aucun transporteur n’a été caractérisé à cejour et leur implication dans la physiologie des coraux n’est que suggérée par la pharmacologie. Durant cette thèse nous avons cloné un gène codant pour un transporteur deHCO3- chez le corail Acropora sp. La conversion de ce HCO3- en CO2 pour la photosynthèse est facilitée par l’acidification de l’environnement proche du Dinoflagellé dans la cellule animale. Cette acidification est causée par une H+-ATPase de type P que nous avons caractérisée. Ce gène est le premier à montrer une expression dépendante de la vie en symbiose chez le symbiote.Nous avons aussi cloné et localisé deux anhydrases carboniques (AC). L’une impliquée dans la calcification et l’autre dans la régulation du pH intracellulaire et l’équilibre entre leCO2 et HCO3-. Une étude pharmacologique de ces deux AC, a identifié des molécules inhibitrices et activatrices qui ont permis des expériences de physiologie in vivo. Celles-ci permettent une analyse plus discriminante du rôle des AC dans la calcification
Coral reefs edification is based on the formation of a calcium carbonate skeleton byscleractinian corals. Many of these reef-building corals establish a symbiotic association with photosynthetic Dinoflagellates. Both processes involve the transport and utilization of inorganic carbon (Ci) coming from seawater for photosynthesis, and from animal metabolismfor calcification. This work focused on the molecular and physiological study of poorlyknown mechanisms that allow the utilization of Ci.Despite the importance of bicarbonate transport, no transporter has been characterized and their role in coral physiology is only suggested by pharmacological experiments. We have cloned a gene encoding a bicarbonate transporter in the coral Acropora sp. The conversion of this bicarbonate into CO2 for photosynthesis is mediated by the acidification of the are asurrounding the Dinoflagellate in the animal cell. This is performed by a P type H+-ATPasethat we characterized here. This is the first gene with a symbiosis-dependent expression in the symbiont.This work also allowed the cloning and the localization of two carbonic anhydrases (CA).The first one is involved in calcification, the second one plays a role in the intracellular pHregulation and the CO2 / HCO3- equilibrium. A pharmacological study of these two enzymes identified inhibitor and activator compounds that have been then used in physiology experiments. This last approach represents a more accurate study of the role of CAs incalcification

L'utilisation conjointe d'un nouveau modele biologique, la microcolonie de corail de stylophora pistillata, et d'un nouveau protocole utilisant le #4#5ca a permis de caracteriser les mecanismes cellulaires impliques dans la calcification des scleractiniaires hermatypiques. Lors de l'utilisation de radioisotopes, les problemes d'adsorption non specifique sont elimines. Ce protocole est caracterise par une phase d'efflux a la fin de l'incubation qui permet de vidanger un compartiment extracellulaire. Quatre compartiments ont ete mis en evidence. Le premier est extracellulaire et correspond au clenteron. Le second, correspondant a la totalite des tissus, est caracterise par un t#1#/#2 de 20 min (ca #t#o#t: 7 nmol ca. Mg#-#1 proteine), son intervention dans le transport du calcium utilise pour la calcification semble indirecte. Le troisieme, implique dans la synthese du squelette (t#1#/#2: 2 min), correspond vraisemblablement a l'ectoderme calicoblastique dont les cellules possedent des canaux calcium sensibles aux inhibiteurs des canaux calcium de type l. La caracterisation moleculaire d'un canal calcium de type l a permis grace a des anticorps de le localiser sur les deux ectodermes. Le transport de calcium dans ce compartiment est de type transcellulaire et est couple probablement a des ca#2#+-atpases. Le quatrieme, correspondant au squelette, est un flux unidirectionnel de 975 pmol ca. Mg#-#1 proteine. Min#-#1. L'etude de l'incorporation de la matrice organique a montre qu'elle est couplee a l'incorporation de calcium dans le squelette. Le tbt, compose present dans certaines peintures anti-salissures, pourrait alterer la calcification en inhibant la synthese de la matrice organique. Une approche en microscopie electronique a permis de confirmer la nature cellulaire des structures d'ancrage, les desmocytes. L'etude de la croissance in situ sur l'atoll de mururoa a permis de correler la croissance a la temperature mais non avec le rayonnement. Dans la zone subsidee, la croissance lineaire est superieure a la zone controle

Les récifs coralliens, majoritairement édifiés par les coraux Scléractiniaires, constituent la plus importante construction biologique à l’échelle mondiale. De nombreux coraux Scléractiniaires établissent une symbiose avec un Dinobionte photosynthétique. Cette symbiose est responsable, entre autres, d’une stimulation de la calcification des coraux en présence de lumière, phénomène décrit sous le terme de “light-enhanced calcification” (LEC). Malgré de nombreuses recherches, les mécanismes responsables de ce phénomène de LEC restent méconnus. Ma thèse a consisté en l’étude de la calcification et du phénomène de LEC chez le corail Stylophora pistillata par une double approche physiologique (caractérisation du phénomène chez cette espèce, cycle journalier, temps de transition) et moléculaire (caractérisation moléculaire et localisation tissulaire d’une anhydrase carbonique impliquée dans le processus de calcification, régulation transcriptionnelle entre les conditions "Jour" et "Nuit")
Scleractinian corals are the main calcifying organisms of coral reefs. Most scleractinian corals establish a symbiotic relationship with phototrophic Dinoflagellates. This symbiosis is responsible for the stimulation of coral calcification by light, a phenomenon called “light enhanced calcification” (LEC). Despite numerous studies performed on this subject, the mechanisms linking photosynthesis of the symbionts to coral calcification remain largely unknown. The aim of the present work is to gain a better understanding of the calcification process and of the “light-enhanced calcification” phenomenon in the scleractinian coral Stylophora pistillata (Esper, 1797), using both physiological (characterization of the LEC phenomenon in S. Pistillata, daily cycle, time transitions) and molecular approaches (molecular characterization and tissular localization of a carbonic anhydrase involved in the calcification process, transcriptional regulation between light and dark conditions)

Les coraux scléractiniaires sont des organismes hétérotrophes, qui capturent du plancton, et autotrophes, de par leur symbiose avec des dinoflagellés photosynthétiques, qui transfèrent à l’hôte la majeure partie du carbone fixé (photosynthétats). L’acquisition et l’allocation de ces nutriments sont deux processus clés expliquant l’expansion des coraux dans des milieux oligotrophes. Malgré l’importance de ces processus, de nombreuses zones d’ombre existent. Les enjeux de cette thèse, réalisée sur un corail tropical (Stylophora pistillata) et un tempéré (Cladocora caespitosa) ont donc été : 1) de développer un modèle permettent de quantifier le transfert de carbone autotrophe des symbiotes à l’hôte et d’estimer le budget de ce carbone; 2) d’estimer l’importance de l’hétérotrophie, notamment lorsque les apports autotrophes sont diminués. Les résultats obtenus ont montré que le transfert de photosynthétats varie de 50 à 90 % selon les conditions environnementales (lumière, nutrition, et pH de l’eau de mer), ce qui influe sur le budget de carbone de la symbiose. Cependant, lorsque la production photosynthétique diminue suite à un stress, le transfert de photosynthétats tend à augmenter, afin de fournir la même quantité de carbone à l’hôte. L’hétérotrophie, chez S. Pistillata, ne permet pas de compenser la privation d’autotrophie lors d’un blanchissement (perte des symbiotes), car les colonies diminuent aussi leur prédation sur le zooplancton. Chez C. Caespitosa, par contre, l’hétérotrophie joue un rôle majeur dans le budget de carbone. Cette espèce s’acclimate aussi très bien à une large gamme de lumières, ce qui la rend autant autotrophe que les espèces tropicales
Scleractinian corals are both heterotroph, since they capture planktonic prey, and autotroph, via their symbiosis with photosynthetic dinoflagellates, which translocate most of the photosynthates to the coral host for its own needs. The acquisition and allocation of these nutrients are key processes explaining the functioning and development of corals in oligotrophic waters. Despite the importance of these processes, many gaps still exist. The aims of this thesis, performed on a tropical (Stylophora pistillata) and a temperate (Cladocora caespitosa) species, were to: 1) develop a model to estimate the autotrophic carbon budget, as well as the rates of photosynthate translocation from the symbionts to the host; 2) assess the importance of heterotrophy, especially in situations where autotrophy is impacted. Results have shown that photosynthate translocation varies between 50 and 90% depending on environmental conditions (irradiance, feeding, and seawater pH), and affects the global carbon budget of the symbiotic association. However, when a stress decreases the photosynthetic production, photosynthate translocation increases to allocate the same amount of carbon to the host. For S. Pistillata, heterotrophy does not compensate for the loss of autotrophy during a bleaching event (loss of symbionts), because the coral colonies also decrease their predation on zooplankton. In contrast, for C. Caespitosa, heterotrophy plays an important role in the carbon budget. Since this species is also very well acclimatised to a wide range of irradiances, it is as autotroph as the tropical species

Les coraux tropicaux constructeurs de récifs sont à l’origine d’écosystèmes extrêmement riches dont dépendent de nombreuses espèces, y compris l’Homme. Aujourd’hui, les changements climatiques représentent toutefois une menace pour la survie des coraux. Afin de comprendre la réponse de ces espèces aux modifications environnementales, il est essentiel d’avoir des informations sur la physiologie de ces espèces-clé. Les travaux conduits au cours de ma thèse ont ainsi permis de caractériser, au niveau mécanistique, les processus affectés par des changements de température chez l’espèce Stylophora pistillata. Pour cela, j’ai employé des approches multiples en partant de l’animal jusqu’au gène. Mes résultats ont montré : 1) que les taux de calcification, de photosynthèse et de respiration sont drastiquement réduits aux extrémités de la fenêtre thermique, 2) l’existence d’un phénomène de « light-enhanced calcification », excepté à basse température, 3) la sous-expression d’un groupe de gènes impliqué dans le transport du carbone inorganique lorsque les taux de calcification sont réduits (stress thermiques et la nuit), 4) la stabilité du pH dans le milieu extracellulaire calcifiant dans tous les traitements, et 5) l’augmentation de la perméabilité paracellulaire conjointement à l’augmentation de la calcification (25°C et le jour). En plus de leur intérêt en recherche fondamentale, ces informations peuvent constituer des outils utiles pour de futures recherches sur le terrain dans le but d’évaluer l’état de santé des coraux et prédire leur devenir dans un monde qui change
Tropical reef-building corals are at the basis of extremely biodiverse ecosystems on which many species depend, including human beings. Today, climate change represents a threat for the future survival of corals, and it is becoming crucial to better understand the physiology of these key species and the mechanisms underlying their responses to environmental change. The work conducted during my PhD focused on the characterization of the processes affected by temperature changes in Stylophora pistillata. For this purpose, I used multiple approaches from the animal to the gene. My results showed that: 1) calcification, photosynthesis and respiration declined drastically at the extremes of the thermal performance window, 2) light-enhanced calcification occurs across the thermal performance window except at low temperature, 3) a group of genes involved in inorganic carbon transport is under-expressed when calcification is reduced (thermal stress and during night), 4) pH in the extracellular calcifying medium remains stable at low and high temperatures, 5) paracellular permeability is highest when calcification increases (25°C and during the day). Information gained from this lab-based study will be useful in guiding further research in the field in order to evaluate coral health and predict the future of coral reefs in a changing world

La linéarité des chromosomes eucaryotes implique la présence d’une chromatine à la structure particulière, appelée télomère, pour contrôler la stabilité du génome et conserver sa fonction. Des changements dans la structure des télomères peuvent déterminer la longévité, la résistance au stress et la susceptibilité de développer certaines pathologies. Notre compréhension sur la contribution des facteurs environnementaux sur la longueur des télomères n’en est qu’à ses balbutiements, tout comme notre connaissance de la diversité des mécanismes de régulation de la taille des télomères dans l’arbre de la vie. Les coraux constructeurs de récifs sont à cet égard des modèles de choix, leurs conditions de vie fixée les empêchant de fuir des conditions défavorables et leur endosymbiose obligatoire avec une micro-algue photosynthétique les exposant à un stress oxydant quotidien. Leurs télomères ne sont pourtant que peu étudiés. Dans ce travail de thèse, j’ai combiné une large étude de terrain sur 3 genres de coraux (deux scléractiniaires, Pocillopora sp. et Porites sp., et un hydrozoaire Millepora sp.) et une étude en conditions contrôlées sur l’espèce modèle Stylophora pistillata dans le but de comprendre le lien entre la variation de la taille des télomères et l'environnement. J’ai observé que la taille des télomères des coraux ne diminuait pas avec l’âge, ni avec la taille des colonies, mais qu’une rupture de la symbiose induite à l’obscurité pouvait induire un raccourcissement des télomères. J’ai aussi montré que des espèces avec des stratégies évolutives différentes avaient des régulations de leurs tailles de télomères différentes, le genre Pocillopora sp. étant contraint à la fois par la génétique et l'environnement tandis que le genre Porites sp. démontrant un incroyable maintien de la taille des télomères en dépit des variations génétiques ou des catégories d'environnements. Cependant, malgré leurs différentes stratégies, la taille des télomères des deux genres étaient négativement corrélées aux variations environnementales, mettant à jour ce paramètre comme crucial et potentiellement perturbateur des mécanismes de maintien de la taille des télomères
The linearity of eukaryotic chromosomes requires the presence of a particular terminal chromatin structure, named telomere, to control the stability and function of genomes. Changes in telomere structure during life can determine longevity, stress resistance and disease susceptibility. Our knowledge on the contribution of environmental factors on telomere length (TL) variability remains at its infancy, as well as the diversity of telomere maintenance mechanisms and ageing strategies existing in the tree of life. In this regard reef building corals are an interesting but yet poorly investigated model to tackle the question of telomere response to environment. Indeed those long lived animals cannot escape external environmental stressors due to their fixed life mode nor internal ones due to the symbiosis, within their gastrodermal cells, with a photosynthetic microalgae. Here I combined an extensive field case study on 3 coral genera (two scleractinians, Pocillopora sp. and Porites sp. and the hydrozoan Millepora sp.) as well as controlled conditions test on the coral model Stylophora pistillata to unravel the possible links between telomere DNA length variation and environmental stress. I found that an absence of TL shortening with age and size in all the investigated corals. I observed a possible impact of dark induced bleaching on TL and different TL dynamics in wild populations. Pocillopora sp. mean TL is constrained both by genetic and environment while Porites sp. has a remarkable ability to maintain its TL regardless of size, genetic and some environment disturbance. Yet both of genera TLs were negatively correlated with seasonal deviations, identifying this environmental parameter as a factor overcoming TL maintenance in genera with different TL dynamics and life-history strategies

Stylophora (Comuta and Mitrata) share the same basic anatomical organization, which consists of a (1) delicate single highly flexible tripartite appendage (aulacophore) inserted into a (2) dorsoventrally flattened theca exhibiting various degrees of asymmetry in its outline. Because of this unique anatomy and the controversy surrounding the morpho-functional interpretation of the single appendage, stylophorans have been interpreted either as stem-group chordates, primitive or highly derived echinoderms close to crinoids. Nowadays, their placement within the phylum Echinodermata is still highly debated, as well as their intrinsic relationships. While there is agreement that cornutes and mitrates are closely related to each other, authors have debated whether cornutes are the monophyletic sister-group to mitrates or a paraphyletic array relative to them. This absence of congruence between analyses is mainly due to the fact that there is no agreement on the exoskeletal plate homologies, the choice of characters and their coding, highly influenced by divergent hypotheses of topological similarity. Our present study provides the first detailed cladistic analysis of all the best-known taxa of stylophorans and benefits from recent discoveries of new taxa that shed light on the origin of major stylophoran groups. Our analysis suggests that mitrates are either polyphyletic deriving from paraphyletic symmetrical boot-shaped cornutes, or a natural group deriving from polyphyletic symmetrical cornutes. In each scenario, mitrates and boot-shaped cornutes derive from a basal stock of symmetrical cornutes. The placement of cornute-like mitrates and symmetrical cornutes is particularly issuing in our topologies and we consider them as transitional taxa between mitrates and cornutes. Palaeobiogeographical reconstructions for stylophorans stayed unexplored for a very long time. Patterns of migration and dispersal for mitrocystitidan mitrates are examined in the present study, as well as intrinsic (biological) and extrinsic (palaeoenvironemental) factors and causes of this dispersion. The colonisation of the continent Laurentia by mitrocystitidan mitrates has been realized 8 times, while the Malvinokaffric realm has been colonized only 6 times. Gondwana has been left 4 times for colonization either in Laurentia and/or in the Malvinokaffric Realm. We suggest that the Hirnantian glaciation must have been an important factor for migrations towards shelters located in Laurentia and in the Malvinokaffric realm. The rise of sea level and then its quick fall during this glaciation is concordant with the pattern of dispersion at least for the Ordovician, as suggested by the increase of diversity during this period. The stylophoran dispersion towards Laurentia and the Malvinokaffric Realm is also concordant with the paleo-currents and paleo-upwellings. Stylophorans are typically adapted to a benthic mode of life on soft substrates, by increasing the surface of their body in contact with the seafloor. We characterize here three different strategies for epibenthic stylophoran taxa: (1) the water strider strategy; (2) spine and fan-shaped elements surrounding the theca to increase the body size; (3) hydrodynamic thecas and sediments-gripping devices on the aulacophore. Since the 2000', research interest has been invigorated by new discoveries in Morocco and its recently described, new echinoderm Lagerstatten, The Fezouata biota is one of the richest and most diversified worldwide echinoderm assemblages and a fantastic continuous preservational window open on Cambrian and Paleozoic communities. The echinoderm distribution is not random and is well-divided into four distinct successive assemblages. This pattern is mainly due to an evolutionary process probably combined with a paleoenvironmental process. Recently, abundant remains of a new mitrate (Echinodelmata, Stylophora) were discovered in a brand new echinoderm Lagerstatte from the Early Floian (Lower Ordovician) in the Fezouata Biota. The new taxon, displays a unique combination of characters, mixing features peculiar to anomalocystitid mitrates but also features only seen in the very basal mitrocystitid mitrates. Its basal position is confirmed by the cladistic analysis. Consequently, the new taxon is interpreted as a transitional form between basal mitrocystitidans and anomalocysitid mitrates.

The Lower Devonian Voorstehoek Formation is a fossil-rich, siliciclastic unit (Ceres Subgroup, Bokkeveld Group, Cape Supergroup) in South Africa. This Emsian unit contains a highly endemic benthic fossil biota characteristic of the cool to cold water Malvinokaffric Realm of southwestern Gondwana. The palaeontological and sedimentological investigations of the Voorstehoek Formation suggest that deposition took place in a shallow marine environment within the storm influenced, proximal part of an offshore transition zone. A relatively diverse, ophiuroid–stylophoran assemblage, well-preserved in the Karbonaatjies obrution bed, was excavated at the study site in the Hex River Pass, Western Cape. In this study the taphonomy, taxonomy and the palaeoautecology of Palaeozoic ophiuroids and stylophorans was investigated using micro CT scans. Over 60 samples were scanned, manually segmented and stitched together to create a virtual 3D model of a portion of the Karbonaatjies obrution bed. This method allowed for the determination of the degree of fossil articulation, fossil orientation and faunal counts, without damaging the delicate echinoderm fossils. Furthermore, the ability to digitally analyse the fossil-rich bed has revealed an echinoderm assemblage composed of over 700 articulated ophiuroids dominated by a proposed new genus and species Gamiroaster tempestatis, over 145 articulated mitrate stylophorans Paranacystis cf. petrii Caster, 1954 and eight Placocystella africana (Reed, 1925). Taphonomic analysis of this ophiuroid–stylophoran assemblage indicates this obrution deposit formed due to rapid burial that smothered a potentially gregarious community during a single storm event. Additionally, the admixture of skeletal debris and intact echinoderms present in the Karbonaatjies obrution bed reflects a complex history with significant time-averaging. This unique assemblage provides a taphonomic window into the marine ecosystems of the Early Devonian, including the structure of an unusual, echinoderm-dominated benthic community that forms part of a much wider fossil biota from the Falkland Islands and Precordillera of Argentina, which formed part of SW Gondwana.

Coral reef ecosystems are under increasing threat from ocean warming and deoxygenation. Mass coral bleaching events in recent years have been linked to marine heatwaves but reporting of hypoxia-induced bleaching has also been increasing. Oxygen availability in coral reefs is driven by community metabolism and they experience a dynamic range of oxygen concentrations throughout diel cycles, hyperoxia during the day and hypoxia during the night. It has been suggested that the highest oxygen concentrations coincide with the hottest part of the day and this may protect marine taxa from high temperatures. We evaluated experimentally whether excess oxygen availability would increase the thermal threshold of the branching coral Stylophora pistillata, from the Southern Red Sea. We did this by exposing coral fragments of this species to varying dissolved oxygen concentrations (hypoxia, normoxia and hyperoxia) and a short-term temperature ramping regime (1˚C h-1). Hyperoxia did extend the thermal tolerance of S. pistillata fragments, with an LT50 of 39.1˚C as opposed to 39.0˚C for the normoxic treatment and 38.7˚C for the hypoxic treatment. Hyperoxia also increased respiration and gross photosynthesis and had a negative effect on photochemical efficiency at high temperatures. Net photosynthesis, P:R ratio and symbiont density were not significantly affected by oxygen concentration. Corals in this experiment displayed exceedingly high thermal thresholds, which were at least 2˚C higher than previously reported for the same species in the Central Red Sea. The corals used in the experiment had previously survived mass bleaching events in 2015 and hence we may have selected for individuals adapted to thermal stress. This is the first study to investigate the role of oxygen in the thermal tolerance of hermatypic corals and the first assessment of thermal thresholds from corals in the Southern Red Sea, where previously thermal thresholds have been based on a 1-2˚C increase in maximum mean monthly temperatures and visual bleaching observations. This highlights the need for increased experimental assessments of thermal thresholds in the Southern regions of the Red Sea and the important role of oxygen in moderating thermal stress.

碩士
國立臺灣大學
海洋研究所
92
The effects of temperature (20, 25 and 28℃) and light intensity (50, 200, 800 μE m-2s-1) on the O2-based and chlorophyll fluorescence of photosystem II (PSII)-based parameters of photosynthesis as well as tissue parameters (chlorophyll a concentration, protein concentration and zooxanthellae density) in the reef coral Stylophora pistillata under different culture time (10, 30, 60, 90 d) was investigated by using respirometry and Diving PAM After different temperature treatments for ten days, coral tissue parameters were similar. The O2-based parameters of photosynthesis, including maximum gross photosynthetic rates (Pgmax), photosynthetic efficiency (?, sub-saturation irradiance (Ik), and Photosystem II (PSII)-based parameters of photosynthesis, including photosynthetic efficiency (? and maximum PSII quantum efficiency (Fv/Fm), were similar under different temperature treatments. However, the maximum rate of ETR (ETRmax) of corals at 25 and 28℃ was two times higher than that of corals at 20℃. In addition, the sub-saturation irradiance (Ik-ETR) of corals was highest at 28℃, and lowest at 20℃. This suggests that fluorescence-based photosynthetic parameters were more sensitive to temperature difference. After different temperature treatments for ninety days, most tissue parameters of corals changed, except the protein concentration and chlorophyll a and c ratio. The chlorophyll a and zooxanthellae density were lowest at 20℃. The O2-based parameters of photosynthesis, such as Pgmax, ?and Ik, were highest at 25℃. The ETRmax of corals was higher at 25℃ and 28℃ than that at 20℃. These may be resulted from the high temperature facilitating the enzyme activity. Gross photosynthesis (GP) and ETR of corals under irradiances below 400 μE m-2s-1 or GP less than 14 μmol O2 m-2s-1 at the three temperature treatments. This suggests that diving-PAM may provide a quick and non-invasive way to estimate primary productivity of corals at least under moderate irradiances. The effect of different temperature and light intensity on ETR and Fv/Fm of Stylophora pistillata was compared under different culture time (0, 10, 30, 60, 90 d). The Fv/Fm was inhibited under high light intensity. The temperature stress would enhance this inhibition. The values of ETRmax were unchanged under medium and low light intensity treatments, but decreased under high light intensity treatment. In addition, the ETRmax was higher with increasing temperature. The ?ETR was inhibited by high light intensity and high temperature. The effect of light intensity on Ik-ETR was different under different temperature treatments. The effects of medium and high light were more obvious with increasing temperature. These results suggest that when corals were under different temperatures and light intensities, they may acclimate in different ways. Coral photosynthesis, however, would more likely be inhibited by high light intensity. Furthermore, when they were stressed by temperature and light intensity synergistically, the impacts on coral photosynthesis would be more serious.

Studies of coral-­associated bacterial communities have repeatedly demonstrated that the microbial assemblages of the coral host are highly specific and complex. In particular, bacterial community surveys of scleractinian and soft corals from geographically diverse reefs continually uncover a high abundance of sequences affiliated with the Gammaproteobacteria genus Endozoicomonas. The role of these bacteria within the complex coral holobiont is currently unknown. In order to localize these cells and gain an understanding of their potential interactions within the coral, we developed a fluorescence in situ hybridization(FISH) approach for reef-­building coral tissues. Using a custom small-­subunit ribosomal RNA gene database, we developed two Endozoicomonas-­specific probes that cover almost all known coral-­associated Endozoicomonas sequences. Probe hybridization conditions were quantitatively evaluated against target and non-­target bacterial cultures using fluorescence microscopy. Using these experimentally tested conditions, probes were then hybridized to the branching coral Stylophora pistillata, obtained from the Red Sea, using whole mount and paraffin embedding techniques. This study allowed preliminary spatial exploration and characterization of Endozoicomonas in coral, which has provided insight into their functional role and interactions within the coral holobiont.

Observing populations at different spatial scales gives greater insight into the specific processes driving genetic differentiation and population structure. Here we determined population connectivity across multiple spatial scales in the Red Sea to determine the population structures of two reef building corals Stylophora pistillata and Pocillopora verrucosa. The Red sea is a 2,250 km long body of water with extremely variable latitudinal environmental gradients. Mitochondrial and microsatellite markers were used to determine distinct lineages and to look for genetic differentiation among sampling sites. No distinctive population structure across the latitudinal gradient was discovered within this study suggesting a phenotypic plasticity of both these species to various environments. Stylophora pistillata displayed a heterogeneous distribution of three distinct genetic populations on both a fine and large scale. Fst, Gst, and Dest were all significant (p-value<0.05) and showed moderate genetic differentiation between all sampling sites. However this seems to be byproduct of the heterogeneous distribution, as no distinct genetic population breaks were found. Stylophora pistillata showed greater population structure on a fine scale suggesting genetic selection based on fine scale environmental variations. However, further environmental and oceanographic data is needed to make more inferences on this structure at small spatial scales. This study highlights the deficits of knowledge of both the Red Sea and coral plasticity in regards to local environmental conditions.

碩士
國立臺灣大學
海洋研究所
92
The purpose of this study is to compare the effects of sea temperature on growth rate and mortality of reef corals, Stylophora pistillata and Seriatopora hystrix. Coral colonies were collected from Nanwan Bay, southern Taiwan. Coral branches were prepared and cultured in mesocosms at three temperature regimes (28, 25 and 20℃, each 2 replicates). The growth of corals was measured at three-week intervals by a buoyant weighting technique. The mean growth rates of S. pistillata and S. hystrix at 25℃(S. pistillata: 0.0126±0.0045 g/g*day; S. hystrix: 0.0253±0.0081 g/g*day) were significantly higher than those at 28℃(S. pistillata: 0.0066±0.0027 g/g*day; S. hystrix: 0.0083±0.0046 g/g*day) and 20℃(S. pistillata: 0.0058±0.0014 g/g*day; S. hystrix: 0.0047±0.0022 g/g*day).The mean growth rates of S. hystrix in two mesocosms at 25℃ were similar and significantly higher than those of S. pistillata. However, the mean growth rates of S. pistillata in two mesocosms at 25℃ were significantly different. The mean growth rates of S. hystrix in two mesocosms at 28℃ were significantly different and did not show a consistant relationship compared to those of S. pistillata. The mean growth rates of S. hystrix in two mesocosms at 20℃ were significantly different, but those of S. pistillata were the same. This suggests that the effects of temperature on growth of the two coral species were different. Growth rates of S. hystrix at 25℃ were stable and higher than those of S. pistillata. However, the effects of temperature on growth rate of S. hystrix may be modified by other factors (e.g., mesocosm effect) in higher or lower temperatures. The mortality of S. pistillata in three temperature treatments was very low, while the partial mortality of S. hystrix at 28℃ (37.5 %) was significantly higher than that at 25 (2.1 %) and 20℃ (2.1 %). This suggests that S. hystrix is more sensitive and vulnerable to high sea temperatures.

Nowadays, corals have a large economic potential and the increasing demand places an enormous pressure on wild reefs. This issue brings new challenges for coral production in terms of increasing production and efficiency. Besides this, climate change and warmer oceans are threatening the future of corals, with several bleaching events occurring worldwide. Many factors that influence the growth and health of the corals have already been extensively studied, however, some factors, such as low temperatures and photoperiod require further research. Temperature and light also play a critical role in the phenomena of coral bleaching, which means that our knowledge about the interaction of these two factors is essential. The main objectives of this research were to find more information to improve the production protocols and better understand the physiology of stony corals under abnormal light and thermal conditions. In this study different combinations of temperatures (20º, 23º, 26º and 29ºC) and photoperiods (8L16D, 12L12D, 16L8D) were tested for a period of one month. Growth and metabolism measurements, zooxanthellae counts and pigments’ analysis were conducted to evaluate the condition, calcification and photosynthetic activity of Stylophora pistillata. No increase in growth was achieved with the extension of the photoperiod, however, a shorter photoperiod revealed to be detrimental to growth after a significant reduction of 25% compared to control treatment. Colonies maintained at 20º and 29ºC suffered reductions on their growth rates independently of the photoperiod regime. Photosynthetic efficiency and concentration of pigments suffered a decrease under the 16h light regime while corals maintained at 8h regime kept their photosynthetic efficiency and increased their pigmentation. Zooxanthellar populations were strongly reduced by low temperatures. The interaction between photoperiod and temperature was observed in photosynthetic efficiency and pigments concentration. These results lead to conclude that the effects of photoperiod are similar to those of light intensity, cold stress presents analogous effects to heat stress, as, the combined effects of photoperiod and temperature are similar to light intensity and temperature.
Na actualidade, os corais têm um potencial económico muito elevado e o aumento da sua procura coloca uma grande pressão sobre os recifes de coral. Este problema trás novos desafios para a produção de corais em termos de aumento da produção e da sua eficiência. Para além disto as alterações climáticas e oceanos mais quentes são uma ameaça ao futuro dos corais, com vários eventos de branqueamento a ocorrer em todo o mundo. Muitos dos factores que influenciam o crescimento e a saúde dos corais foram já extensamente estudados, no entanto, alguns factores como a temperatura ou o fotoperíodo requerem mais investigação. Boas performances a temperaturas de produção mais baixas ou em fotoperíodos mais curtos podem representar uma redução no consumo energético, aumentando a viabilidade económica da produção. Os principais objectivos deste estudo serão encontrar pistas para melhorar os protocolos de produção e melhorar o nosso entendimento sobre a fisiologia dos corais sob condições anormais de temperatura e luz. O propósito do procedimento experimental é testar diferentes combinações de temperaturas (20º, 23º, 26º e 29ºC) e fotoperíodos (8L16D, 12L12D, 16L8D) com a espécie Stylophora pistillata. Medições de taxas de crescimento, de consumo e produção de oxigénio, contagem de zooxantelas e análises de pigmentos fotossintéticos e carotenoides serão levados a cabo para avaliar a condição, calcificação e actividade fotossintética de desta espécie de coral duro. A experiencia durou 1 mês e meio e foi interrompida devido ao surto de uma doença infeciosa e contagiosa que levou à morte dos corais. Os resultados não demonstraram incremento das taxas de crescimento em conjugação com a extensão do fotoperíodo. No entanto, uma redução do fotoperíodo demonstrou ser negativa para o crescimento com uma redução de 25% comparado com o grupo de controlo. Os corais mantidos a 20º e 29º sofreram uma redução na sua taxa de crescimento, independentemente do fotoperíodo a que estiveram expostos. A eficiência fotossintética e a concentração de pigmentos dos corais sofreram uma redução quando expostas a 16 horas de luz enquanto que corais expostos a 8 horas de luz mantiveram a sua eficiência fotossintética e aumentaram a sua pigmentação. A densidade de zooxantelas foi intensamente reduzida pelas temperaturas mais baixas. Ocorreu interação entre o fotoperíodo e as temperaturas na eficiência fotossintética e na concentração de pigmentos. Estas observação levam a concluir que os efeitos do fotoperíodo são similares aos da intensidade luminosa, que baixas temperaturas causam efeitos análogos aos das temperaturas elevadas, bem como os efeitos combinado do fotoperíodo e da temperatura são semelhantes ao da intensidade luminosa e da temperatura.

碩士
國立高雄海洋科技大學
海洋生物技術研究所
100
The marine bacterium, Paracoccus stylophorae KTW-16, was isolated from the coral Stylophora pistillata, collected from the Kenting sea waters southern Taiwan. In the marine broth (MB) without extra carbon source, P. stylophorae KTW-16 was capable of synthesizing 80 mol% 3-hydroxybutyrate (3-HB) and 20 mol% 3-hydroxyvalerate (3-HV) of PHA copolymer. At 25oC, P. stylophorae KTW-16 accumulated 30% PHA with 75 mol% 3-HB and 25 mol% 3-HV. The 3-HV monomer composition of PHA was decreased with the increase of tryptone in MB. According to this result, the effect of amino acid supplemented to the MB on PHA accumulation was tested. The addition of threonine, valine, and isoleucine significantly enhanced the 3-HV monomer composition. In addition, under the presence of β-oxidation pathway inhibitor acrylic acid in the medium, P. stylophorae KTW-16 synthesized 3-HB, 3-HV and 3-hydroxyhexanoate (3-HHx) terpolymer. The polymer structure was by nuclear magnetic resonance spectroscopy (13C-NMR) analyzed. It confirmed that three monomers were randomly copolymerized. This study also constructed a genomic library of P. stylophorae KTW-16. The PHA synthase gene was cloned. The in vivo substrate specificity of PHA synthase of P. stylophorae KTW-16 was analyzed in the PHA mutant Pseudomonas putida GPp104 PHA-. The PHA synthase of P. stylophorae KTW-16 biosynthesis 80 mol% 3-HB, 18 mol% 3-HHx and 2 mol% 3-hydroxyoctanoate (3-HO) of PHA from 0.4% octanoate as the carbon source, compared with that of Ralstonia eutropha H16 (PhaCH16) synthesizing 96 mol% 3-HB, 3 mol% 3-HHx and 1 mol% 3-HO of PHA. The above results strongly suggested that the PHA synthase of P. stylophorae KTW-16 was of broader substrate specificity than PhaCH16.