Symbiotic Zooxanthellae Research Articles

Light induces changes in activities of Na(+)/K(+)-ATPase, H(+)/K(+)-ATPase and glutamine synthetase in tissues involved directly or indirectly in light-enhanced calcification in the giant clam, Tridacna squamosa.

The objective of this study was to determine the effects of 12 h of exposure to light, as compared with 12 h of exposure to darkness (control), on enzymatic activities of transporters involved in the transport of NH+4 or H+, and activities of enzymes involved in converting NH+4 to glutamate/glutamine in inner mantle, outer mantle, and ctenidia of the giant clam, Tridacna squamosa. Exposure to light resulted in a significant increase in the effectiveness of NH+4 in substitution for K+ to activate Na+/K+-ATPase (NKA), manifested as a significant increase in the Na+/NH+4-activated-NKA activity in the inner mantle. However, similar phenomena were not observed in the extensible outer mantle, which contained abundant symbiotic zooxanthellae. Hence, during light-enhanced calcification, H+ released from CaCO3 deposition could react with NH3 to form NH+4 in the extrapallial fluid, and NH+4 could probably be transported into the shell-facing inner mantle epithelium through NKA. Light also induced an increase in the activity of glutamine synthetase, which converts NH+4 and glutamate to glutamine, in the inner mantle. Taken together, these results explained observations reported elsewhere that light induced a significant increase in pH and a significant decrease in ammonia concentration in the extrapallial fluid, as well as a significant increase in the glutamine concentration in the inner mantle, of T. squamosa. Exposure of T. squamosa to light also led to a significant decrease in the N-ethylmaleimide (NEM)-sensitive-V-H+-ATPase (VATPase) in the inner mantle, and significant increases in the Na+/K+-activated-NKA, H+/NH+4-activated-H+/K+-ATPase, and NEM-sensitive-VATPase activities in ctenidia, indicating that light-enhanced calcification might perturb Na+ homeostasis and acid/base balance in the hemolymph, and might involve the active uptake of NH+4 from the environment. This is the first report on light having direct enhancing effects on activities of certain transporters/enzymes related to light-enhanced calcification in the inner mantle and ctenidia of T. squamosa.

Description of a new species of giant clam (Bivalvia: Tridacnidae) from Ningaloo Reef, Western Australia

A new species of giant clam from northern Australian coastal waters is distinguished principally on genetic evidence. Of Recent tridacnids, Tridacna ningaloo n. sp. is morphologically closest to the most widespread species in the Indo-Pacific, Tridacna maxima (Röding, 1798), yet genetically closest to the species pair T. squamosa Lamarck, 1819 plus T. crocea Lamarck, 1819. Genotype data are provided for the type material of T. ningaloo n. sp. The greatest significance of this new, cryptic species is that it casts doubt on the correctness of the ‘historical’ giant clam species defined solely on conchological characters, particularly T. maxima. This paper supports the retention of all giant clams in the family Tridacnidae, as distinct from the Cardiidae, because of their numerous morphological apomorphies, specialised ecological niche, and independent acquisition of symbiotic zooxanthellae.

Application of chlorophyll fluorescence technique in the study of coral symbiotic zooxanthellae micro-ecology

Mutualistic relationship between coral polyps and their symbiotic zooxanthellae living within their tissues are the most essential features of a coral reef ecosystem. In this symbiotic system, the coral polyps provide a protected habitat, carbon dioxide and nutrients needed for photosynthesis to zooxanthellae; in turn, the symbiotic zooxanthellae provide food as products of photosynthesis to coral polyps. The Photosynthesis of zooxanthellae is therefore an important process of this symbiotic system as well as the development of the whole coral reef ecosystem. The recent application of chlorophyll fluorescence technique in the study of the zooxanthellae’s photosynthesis has greatly improved our understanding on the micro-ecology of corals and the symbiotic zooxanthellae. This paper summarizes the recent progress as the following aspects: (1) The ecological characteristics of the photosynthesis of symbiotic zooxanthellae, such as the diurnal and seasonal changes in the photochemical efficiency of the zooxanthellae, and the relationship between zooxanthellae photosynthesis and the world-wide coral bleaching. (2) The mechanism of corals acclimating to the changes of irradiance via spatial and temporal photoacclimations, including the corals’ photobiology; zooxanthella size, pigmentation, location and clade, and the relationship between light extremes and the corals’ metabolism and calcification. (3) The understanding of the response of zooxanthellae to various environmental stresses, such as long-term changes in the chlorophyll fluorescence of bleached and recovering corals; the tolerance of corals to thermal bleaching; the changes to photosystem II of symbiotic zooxanthellae after heat stress and bleaching. Due to the above findings, the chlorophyll fluorescence values of those coral species sensitive to environmental changes have been utilized as indicators of coral health as well as the status of coral reef ecosystems. In summary, the chlorophyll fluorescence technique has great potential in the understanding, monitoring, protecting and managing coral reefs.

A Snapshot of a Coral “Holobiont”: A Transcriptome Assembly of the Scleractinian Coral, Porites, Captures a Wide Variety of Genes from Both the Host and Symbiotic Zooxanthellae

Massive scleractinian corals of the genus Porites are important reef builders in the Indo-Pacific, and they are more resistant to thermal stress than other stony corals, such as the genus Acropora. Because coral health and survival largely depend on the interaction between a coral host and its symbionts, it is important to understand the molecular interactions of an entire “coral holobiont”. We simultaneously sequenced transcriptomes of Porites australiensis and its symbionts using the Illumina Hiseq2000 platform. We obtained 14.3 Gbp of sequencing data and assembled it into 74,997 contigs (average: 1,263 bp, N50 size: 2,037 bp). We successfully distinguished contigs originating from the host (Porites) and the symbiont (Symbiodinium) by aligning nucleotide sequences with the decoded Acropora digitifera and Symbiodinium minutum genomes. In contrast to previous coral transcriptome studies, at least 35% of the sequences were found to have originated from the symbionts, indicating that it is possible to analyze both host and symbiont transcriptomes simultaneously. Conserved protein domain and KEGG analyses showed that the dataset contains broad gene repertoires of both Porites and Symbiodinium. Effective utilization of sequence reads revealed that the polymorphism rate in P. australiensis is 1.0% and identified the major symbiotic Symbiodinium as Type C15. Analyses of amino acid biosynthetic pathways suggested that this Porites holobiont is probably able to synthesize most of the common amino acids and that Symbiodinium is potentially able to provide essential amino acids to its host. We believe this to be the first molecular evidence of complementarity in amino acid metabolism between coral hosts and their symbionts. We successfully assembled genes originating from both the host coral and the symbiotic Symbiodinium to create a snapshot of the coral holobiont transcriptome. This dataset will facilitate a deeper understanding of molecular mechanisms of coral symbioses and stress responses.

Review of coral reef ecosystem remote sensing

Coral reef communities face unprecedented pressures at local, regional and global scales as a consequence of climate change and anthropogenic disturbance. Remote sensing, from satellites or aircraft, is possibly the only means to measure the effects of such stresses at appropriately large spatial scales. In the past 30years, remote sensing of coral reefs has made rapid progress. However, the current technology is still not mature enough to monitor complicated coral reef ecosystems. Compared with foreign research in this field, our work lags far behind. There are still deficiencies in many aspects, such as basic data collection, theoretical research and platform construction. In our nation, it is even unclear how coral reefs disperse and where they may be unhealthy. In this paper, general characteristics of coral reef ecosystems and spectral features of different reef benthos have been summarized, based initially on a review of relevant literature in recent years. Based on the spectral separability of different reef types or benthos, remote sensing can be used to monitor two aspects of coral reefs: (1) Measurement of the ecological properties of reefs. (2) Health assessment of the coral reef ecosystem. In the first part, optical remote sensing methods are widely used to map reef geomorphology and habitats or biotopes. The investigation of geomorphologic zonation has proven to be one of the most successful applications, as different geomorphologic zones are associated with characteristic benthic community structures and occur at spatial scales of tens to hundreds of meters, they are amenable to remote detection by moderate to high resolution sensors. With more and more attention on the ecological problems of coral reefs, a number of studies have used high resolution sensors to map reef communities. The number of classes distinguishable depends on many factors, including the platforms, resolution (spectral, spatial and temporal resolution) and environmental conditions (water depth, water clarity, surface roughness, etc.). Compared with deep water color remote sensing, or terrestrial remote sensing, three techniques for the measurement of reef ecological properties are examined in this paper: (1) Coral reef classification system using remote sensing. (2) Techniques of sea surface correction and water column correction. (3) Techniques of coral reef information extraction from images. In terms of the complexity of coral reef ecosystems, the current techniques still need further improvement or optimization. In the health assessment of coral reef ecosystems, there are two ways to carry out the monitoring using remote sensing: (1) Monitoring the pigment or symbiotic zooxanthellae contents in corals. (2) Measuring the environmental properties of reefs. The first way is theoretically feasible, but difficult to achieve in practice. Currently, most reef health assessments are carried out by measuring environmental parameters, including sea surface temperature, solar radiation, ultraviolet radiation, water color, wind speed and direction, rainfall, ocean acidification, sea level, etc., of which sea surface temperature has been routinely measured by NOAA to monitor coral bleaching. In addition to the contents above, this article puts forward five main prospects for development in the future: (1) Establishment of a coral reef classification system using remote sensing. (2) Satellite launch for monitoring coral reefs. (3) Theoretical and methodological development. (4) Establishment of a spectral database for different reef benthos. (5) Integrated application of multi-source remote sensing data. It is hoped that the information provided here will be a reference for subsequent similar studies.

Metal accumulation and sublethal effects in the sea anemone, Aiptasia pallida, after waterborne exposure to metal mixtures

The marine environment is subjected to contamination by a complex mixture of metals from various anthropogenic sources. Measuring the biological responses of organisms to a complex mixture of metals allows for examination of metal-specific responses in an environmentally realistic exposure scenario. To address this issue, the sea anemone, Aiptasia pallida was exposed to a control and a metal mixture (copper, zinc, nickel, and cadmium) at three exposure levels (10, 50, and 100μg/L) for 7days. Anemones were then transferred to metal-free seawater for an additional 7days after the metal exposure to assess metal depuration and recovery. Metal accumulation, activity of the enzymes catalase, glutathione reductase, and carbonic anhydrase, as well as, cell density of the symbiotic zooxanthellae were measured over 14days. Metal accumulation in A. pallida occurred in a concentration dependent manner over the 7-day exposure period. Altered enzyme activity and tentacle retraction of the host, as well as decreased zooxanthellae cell density were observed responses over the 7days, after exposure to a metal concentration as low as 10μg/L. Metal depuration and physiological recovery were dependent on both the metal and the exposure concentration. Understanding how A. pallida and their symbionts are affected by metal exposures in the laboratory may allow better understanding about the responses of symbiotic cnidarians in metal polluted aquatic environments.

무기영양염 농도와 수온 상승이 산호 갈색공생조류의 밀도에 미치는 영향

The coral symbiotic algae zooxanthellae is often expelled from the host as the host coral is under physiological stress, causing the coral to turn completely white. Such coral bleaching events are occurring more frequently with the increase in the global warming, ocean acidification and increased level of anthropogenic impacts such as eutrophication. In the present study, we investigated the effects of inorganic nutrients including ammonium, nitrate, phosphate and elevated water temperature on the symbiotic zooxanthellae density in the fragment of branching coral Acropora nobilis. Zooxanthellae density in the host coral decreased 8 hrs after the experiment at a given elevated water temperature (32℃, p ＜ 0.05). In contrast, no clear coral bleaching or decrease in the symbiotic algae density was observed from the branching coral exposed to a normal water temperature of 30℃ and high levels of nutrients such as 20 μM of NH₄Cl, 20 μM of NaNO₃ and, 10 μM KH₂PO₄. Accordingly, the data indicated high water temperature is one of the stressful factors to cause bleaching in A. nobilis, whereas the high levels of nutrients is not a factor. It is believed that the results obtained in the present study are useful as baseline information in the management of the coral reefs.

Identification and characterization of microsatellite markers for scleractinian coral Galaxea fascicularis and its symbiotic zooxanthellae

Nine polymorphic microsatellites markers were identified for Galaxea fascicularis symbionts and characterized in 29 samples from two populations. Four of them were derived from coral genome with 5–11 alleles, and the expected and observed heterozygosities ranging 0.67–0.89 and 0.25–0.69 respectively. Five were derived from zooxanthella genome amplified 0–3 alleles/locus per individual, while 2–4 alleles/locus with totally 13 genotypes in the two populations, which likely implied multiple DNA-polymorphic Symbiodinium species associated with single host and the populations. The genetic diversity of the two coral host populations was significantly greater than that of zooxanthella populations. These markers should be useful in various genetic applications involving both the coral host and the zooxanthella.

Ulcerated yellow spot syndrome: implications of aquaculture-related pathogens associated with soft coral Sarcophyton ehrenbergi tissue lesions

We introduce a new marine syndrome called ulcerated yellow spot, affecting the soft coral Sarcophyton ehrenbergi. To identify bacteria associated with tissue lesions, tissue and mucus samples were taken during a 2009 Indo-Pacific research expedition near the Wakatobi Island chain, Indonesia. Polymerase chain reaction targeting the 16S rDNA gene indicated associations with the known fish-disease-causing bacterium Photobacterium damselae, as well as multiple Vibrio species. Results indicate a shift toward decreasing diversity of bacteria in lesioned samples. Photobacterium damselae ssp. piscicida, formerly known as Pasteurella piscicida, is known as the causative agent of fish pasteurellosis and in this study, was isolated solely in lesioned tissues. Globally, fish pasteurellosis is one of the most damaging fish diseases in marine aquaculture. Vibrio alginolyticus, a putative pathogen associated with yellow band disease in scleractinian coral, was also isolated from lesioned tissues. Lesions appear to be inflicting damage on symbiotic zooxanthellae (Symbiodinium sp.), measurable by decreases in mitotic index, cell density and photosynthetic efficiency. Mitotic index of zooxanthellae within infected tissue samples was decreased by ~80%, while zooxanthellae densities were decreased by ~40% in lesioned tissue samples compared with healthy coral. These results provide evidence for the presence of known aquaculture pathogens in lesioned soft coral and may be a concern with respect to cross-species epizootics in the tropics.

MỘT SỐ ĐẶC ĐIỂM SINH HỌC CỦA SAN HÔ TRONG ĐIỀU KIỆN TỰ NHIÊN VÀ NUÔI GIỮ

Based on the reef building ability relying on symbiotic zooxanthellae, corals can be classified into reef building hermatypic corals and non reef building ahermatypic corals. Based on the presence or absence of outer skeleton, corals can be divided into stony corals and soft corals. For the purpose of feeding, the corals can be classified into large/long polyp stony (LPS) and small/short polyp stony (SPS) corals. All soft corals have eight tentacles on the polyps so called “Octocorallia”. Almost all the hermatypic corals are colonial, with individual polyps. The autotrophic mode of feeding is majority mode in the hermatypic corals with 50 - 95% of the energy budget from photosynthesis depending on species. However, the corals possess the ability of three hetrotrophic modes of feeding: predatory prey capture by the polyps; Sedimentary filter feeding using mucus nets and consume dissolved organic matter through cell membranes. In culture condition, the common food for corals is nauplii of Artemia salina. Besides, corals can consume processed seafood with suitable sizes. Most corals are hermaphroditic, some corals are gonochorism.Sexual and asexual reproduction is observed in corals. Competitive and defensive mechanisms of corals include rapid growth, aggressive structures, sweeper tentacles and toxic compounds. Suitable environmental parameters for corals in the wild and culture conditions: light intensity from 30 - 80% photosynthesis available ratio (PAR0), temperature 23 - 270C; pH 8 - 8.45; alkalinity 2.5 - 4meq/L (7 - 11dkH); salinity 35‰; concentrations of the mineral nutrition are similar to natural marine water (NH+4: 3.8µM/L; NO3--: 3.8µM/L; PO4--: 0.56µM/L); calcium 350 - 450ppm; strontium 8 - 10ppm; the presense of water flow providing oxygen and food transfer for corals, concurrently, sedimentation prevention and anti-fouling on surface of the corals.

MỘT SỐ ĐẶC ĐIỂM SINH HỌC CỦA SAN HÔ TRONG ĐIỀU KIỆN TỰ NHIÊN VÀ NUÔI GIỮ

Based on the reef building ability relying on symbiotic zooxanthellae, corals can be classified into reef building hermatypic corals and non reef building ahermatypic corals. Based on the presence or absence of outer skeleton, corals can be divided into stony corals and soft corals. For the purpose of feeding, the corals can be classified into large/long polyp stony (LPS) and small/short polyp stony (SPS) corals. All soft corals have eight tentacles on the polyps so called “Octocorallia”. Almost all the hermatypic corals are colonial, with individual polyps. The autotrophic mode of feeding is majority mode in the hermatypic corals with 50 - 95% of the energy budget from photosynthesis depending on species. However, the corals possess the ability of three hetrotrophic modes of feeding: predatory prey capture by the polyps; Sedimentary filter feeding using mucus nets and consume dissolved organic matter through cell membranes. In culture condition, the common food for corals is nauplii of Artemia salina. Besides, corals can consume processed seafood with suitable sizes. Most corals are hermaphroditic, some corals are gonochorism.Sexual and asexual reproduction is observed in corals. Competitive and defensive mechanisms of corals include rapid growth, aggressive structures, sweeper tentacles and toxic compounds. Suitable environmental parameters for corals in the wild and culture conditions: light intensity from 30 - 80% photosynthesis available ratio (PAR0), temperature 23 - 270C; pH 8 - 8.45; alkalinity 2.5 - 4meq/L (7 - 11dkH); salinity 35‰; concentrations of the mineral nutrition are similar to natural marine water (NH+4: 3.8µM/L; NO3--: 3.8µM/L; PO4--: 0.56µM/L); calcium 350 - 450ppm; strontium 8 - 10ppm; the presense of water flow providing oxygen and food transfer for corals, concurrently, sedimentation prevention and anti-fouling on surface of the corals.

Coral reefs in the South China Sea: Their response to and records on past environmental changes

This paper reviews both the recent and longer-term (Holocene) ecological history of coral reefs in the South China Sea (SCS). (1) Local ecological monitoring since the 1960s shows that the coral reefs in the South China Sea have declined dramatically, reflecting the rapid decrease of living coral cover and the great loss of symbiotic zooxanthellae. Collectively, this has led to a significant decrease of annual CaCO3 production. Heavy anthropogenic activities and global warming are recognized as major triggers of the observed coral reef degradation. Observations show that the modern coral reefs in the SCS are a source of atmospheric CO2 in summer. (2) Coral reefs of the SCS have been widely used to reveal longer-term environmental variations, including Holocene high-resolution sea surface temperature (SST) and abrupt climate events, millennial-scale El Nino variations, millennial- and centennial-scale sea level oscillations, strong and cyclic storm activities, East Asian monsoon intensities, variation in seawater pH, and recent seawater pollution. (3) Coral reefs of the southern SCS have experienced repeated episodes of bleaching over the last 200 years due to high SST and intense El Nino events; coral reefs of the northern SCS suffered high levels of mortality during several abrupt winter cold-water bleaching events during the middle Holocene warm period. On average, recovery after the middle Holocene cold-bleaching took 20–30 years; recovery following other middle Holocene environmental stresses took approximately 10-20 years. Such findings have significantly contributed to the understanding of the present ecological pressures faced by the coral reefs in the SCS, the histories of Holocene climate/environment changes, and the long-term models of coral reef responses to various past environmental changes.

Gulf spill two years out

Summary Two years on, the national spotlight seems to have turned away from the Gulf oil spill, but a massive assessment of the environmental impacts is quietly under way. As Cyrus Martin reports, several recent observations, and a study of deepwater coral communities, suggest we may not be out of the woods yet.

Coral bleaching at Little Cayman, Cayman Islands 2009

The global rise in sea temperature through anthropogenic climate change is affecting coral reef ecosystems through a phenomenon known as coral bleaching; that is, the whitening of corals due to the loss of the symbiotic zooxanthellae which impart corals with their characteristic vivid coloration. We describe aspects of the most prevalent episode of coral bleaching ever recorded at Little Cayman, Cayman Islands, during the fall of 2009. The most susceptible corals were found to be, in order, Siderastrea siderea, Montastraea annularis, and Montastraea faveolata, while Diplora strigosa and Agaricia spp. were less so, yet still showed considerable bleaching prevalence and severity. Those found to be least susceptible were Porites porites, Porites astreoides, and Montastraea cavernosa. These observations and other reported observations of coral bleaching, together with 29 years (1982–2010) of satellite-derived sea surface temperatures, were used to optimize bleaching predictions at this location. To do this a Degree Heating Weeks (DHW) and Peirce Skill Score (PSS) analysis was employed to calculate a local bleaching threshold above which bleaching was expected to occur. A threshold of 4.2 DHW had the highest skill, with a PSS of 0.70. The method outlined here could be applied to other regions to find the optimal bleaching threshold and improve bleaching predictions.

Substrate Kinetics of DMSP-lyases in Various Cultured Symbiodinium Strains

In marine algae, the conversion of the multifunctional metabolite dimethylsulfoniopropionate (DMSP) to dimethylsulfide (DMS) occurs via DMSP-lyase enzymes. Apparent substrate kinetic properties of DMSP-lyases in algae have revealed high levels of variability. Some algal dinoflagellates, including symbiotic zooxanthellae (genus Symbiodinium) produce high intracellular levels of DMSP and DMSP-lyase capabilities vary among specific Symbiodinium strains. To examine the enzyme kinetic properties of DMSP-lyases in zooxanthellae, we used five cultured Symbiodinium microadriaticum (fruedenthal) strains (ccMP 421, 828, 829, 830, 1633) to optimize in vivo DMSP-lyase assay parameters. Optimal activity occurred at ?30 °c with higher enzyme activity at pH 8 compared to pH 7. Further studies were carried out to examine the enzyme kinetic parameters Vmax and Km in two zooxanthellae strains, ccMP 829 and 1633, that differ in their DMSP-lyase basal activity (high and low activity, respectively). Both zooxanthellae strains showed lower half saturation constants for DMSP (range of Km = 0.008-0.124 mM) compared to most other marine phytoplankton tested to date. Vmax values (?mol DMS Lcell volume-1 min-1) increased slightly or by 2.7-fold in strains 1633 and 829, respectively, in conjunction with decreasing growth rates in batch cultures and parallel increases in intracellular DMSP concentrations in strain 829.

Foods of Velella velella (Cnidaria: Hydrozoa) in algal rafts and its distribution in Irish seas

The pleustonic hydrozoan, Velella velella, occurs throughout tropical to cold-temperate oceans of the world and sometimes are stranded in masses along hundreds of kilometers of beaches. In June 2009, we encountered algal rafts in the Celtic Sea containing many V. velella that we immediately preserved for gut content analysis. Available prey were enumerated from raft-associated fauna and zooplankton sampled nearby. The identifiable prey (331) in V. velella comprised 78% raft-associated prey (primarily harpacticoid copepods, cumaceans, small fish) and 22% pelagic prey (calanoid copepods, barnacle nauplii, fish eggs). Comparison of ingested with available prey showed selection for fish eggs and small fish, among others; therefore, the null hypothesis, that V. velella consumed all available prey equally, was rejected. Transport by wind and water concentrate Velella spp. in convergences with algal rafts, which suggests that they are important predators of raft—as well as pelagic fauna. A visual survey in September 2004 across the Celtic Sea and beach-stranding data show that V. velella is very abundant in Irish waters at times. Its circumpolar abundance, consumption of pelagic prey and production from symbiotic zooxanthellae, and mass deposition on beaches suggest that V. velella is important in open-ocean carbon cycling and in transport of pelagic production to landmasses.

Giant Clam Aquaculture: a Review on Induced Spawning and Larval Rearing

Giant clams are the largest extant bivalves and widespread inhabitants of the Indo-Pacific coral reefs. These organisms are particularly sought after by the food industry because of their large mantle and adductor muscle, while also are relevant to the aquarium trade market. The aquaculture of giant clams is dependent of a land-based hatchery divided in several tanks with different purposes for larval rearing. Prior to reproductive events, broodstock are conditioned and gametogensis is stimulated by frequent food additions, increased photoperiod and intense physical-chemical stability at optimum conditions. Several different methods can be employed to induce spawning, most notoriously the intragonadal injection of serotonin, thermal stress and addition of macerated gonadal tissue of a conspecific. The success of the method is based on spawning occurrence, time for response and events of broodstock mortality. After spawning, gametes are fertilized and a succession of planktonic larval stages is cultured in hatching tanks and raceways. Embryonic development lasts for approximately 12 hours until the hatch of free-swimming and non-feeding trochophore larvae. After 24 hours post-fertilization larvae morph into veliger stage, made evident by the presence of calcium carbonate shells and velum. Veliger larva are fed with live or preserved phytoplankton and must also acquire symbiotic zooxanthellae. The last stage is the pediveliger stage at approximately one week post-fertilization, when settlement takes place and metamorphosis is soon attained.

Influence of heterotrophic feeding on the survival and tissue growth rates of Galaxea fascicularis (Octocorralia: Occulinidae) in aquaria

The propagation and growth of scleractinian corals under aquaculture conditions could reduce the pressure of extractive fishing for ornamental species. To fulfil their growth requirements, corals rely on a combination of photosynthetic products translocated from symbiotic zooxanthellae, and particulate heterotrophic sources. In aquaculture, the latter is provided by Artemia sp. nauplii as they provide adequate nutrition and promote optimal growth and survival. In this study, we evaluated feeding rates and estimated growth rates of cultured scleractinian corals. Polyp and colonial nubbins of the coral Galaxea fascicularis were randomly assigned to each of three tanks within three naturally lit systems under standard conditions. Corals were subjected to three feeding treatments: i) fed once or ii) three times weekly, or iii) unfed until the end of the trial (two months). The survival rates were 98.7% and 100% for the colonial and polyp forms, respectively. Ingestion rates of Artemia salina nauplii between the three feeding treatments were significantly higher for specimens fed 3-times a week compared to those two treatments involving a lower feeding frequency (individual prey items polyp−1 20min−1: 8 vs. ≤ 4, respectively), but growth rates of colonial and polyp forms were not significantly different with respect to feeding frequency. Mean rate of new polyp growth was ca. 4 polyps nubbin−1 week−1 for colonial form and ca. 1 polyp polyp−1 week−1 for the polyp form. The high survival and growth rates of G. fascicularis, coupled with an apparent low heterotrophic prey requirement, make this species an ideal candidate for commercial propagation in aquaculture.

Faune corallienne des récifs toarciens du Moyen Atlas marocain, première approche

Abstract Des récifs ont été décrits dans le Toarcien supérieur du Moyen Atlas Marocain [Elmi et al., 2002]. Ils sont localisés dans le synclinal de Awragh-Afennourir (Moyen Atlas occidental) immédiatement au sud du Moyen Atlas tabulaire. Ce sont des biohermes placés au sommet de blocs basculés. Leur épaisseur varie de 1 à 12 m. Ils reposent sur une formation datée de la zone à Levisoni, sous zone à Gemma et sont couverts par des sédiments appartenant à la partie supérieure de la zone à Meneghini. Leur paléolatitude était de 18°N. Un ensemble de 18 échantillons de coraux collectés par S. Elmi sont ici analysés. Ils constituent un témoignage exceptionnel de faune corallienne récifale pour cet étage. Les taxons appartenant aux genres Cladophyllia, Diplocoenia ?, Montlivaltia (deux espèces), Thecosmilia (deux espèces), Isastrea ?, Latomeandra, Periseris, Microphyllia (trois espèces), et Proleptophyllia (deux espèces), ont été identifiés. La faune inclut 12 formes coloniales et 7 solitaires. Parmi les spécimens coloniaux, les formes méandroïdes avec un haut niveau d’intégration colonial sont bien représentées et fournissent un argument fort pour la présence de zooxanthelles symbiotiques. L’examen des textures micritiques et des croûtes microbialitiques, associé avec le développement important des microarchitectures pennulaires suggèrent un récif sous le niveau d’action des vagues de beau temps et des eaux plutôt mésotrophiques. Les coraux, leur forme et leur diversité, permettent de diagnostiquer des récifs de zone photique, à une profondeur et une latitude optimale. Les extensions stratigraphiques de plusieurs genres sont agrandies : nouvelle première occurrence pour Cladophyllia, Latomeandra et Periseris (peut être aussi Diplocoenia) et nouvelle dernière occurrence pour Proleptophyllia classiquement considéré comme Pliensbachien. La seule monographie disponible à caractère général sur les coraux du Lias du Maroc [Beauvais, 1986] identifie 15 taxons génériques pour le Toarcien. Tous proviennent du Haut Atlas et seulement 3 taxons sont communs avec les résultats présentés ici. La vue générale est celle d’une faune qui ressemble davantage à celle des communautés récifales du Dogger qu’à celle du Pliensbachien.

Carotenoids in Marine Invertebrates Living along the Kuroshio Current Coast

Carotenoids of the corals Acropora japonica, A. secale, and A. hyacinthus, the tridacnid clam Tridacna squamosa, the crown-of-thorns starfish Acanthaster planci, and the small sea snail Drupella fragum were investigated. The corals and the tridacnid clam are filter feeders and are associated with symbiotic zooxanthellae. Peridinin and pyrrhoxanthin, which originated from symbiotic zooxanthellae, were found to be major carotenoids in corals and the tridacnid clam. The crown-of-thorns starfish and the sea snail D. fragum are carnivorous and mainly feed on corals. Peridinin-3-acyl esters were major carotenoids in the sea snail D. fragum. On the other hand, ketocarotenoids such as 7,8-didehydroastaxanthin and astaxanthin were major carotenoids in the crown-of-thorns starfish. Carotenoids found in these marine animals closely reflected not only their metabolism but also their food chains.