Gambierdiscus (Gonyaulacales, Dinophyceae) diversity in Vietnamese waters with description of G. vietnamensis sp. nov.

Viet Nam has a coastline of 3200 km with thousands of islands providing diverse habitats for benthic harmful algal species including species of Gambierdiscus. Some of these species produce ciguatera toxins, which may accumulate in large carnivore fish potentially posing major threats to public health. This study reports five species of Gambierdiscus from Vietnamese waters, notably G. australes, G. caribaeus, G. carpenteri, G. pacificus, and G. vietnamensis sp. nov. All species are identified morphologically by LM and SEM, and identifications are supported by molecular analyses of nuclear rDNA (D1-D3 and D8-D10 domains of LSU, SSU, and ITS1-5.8S-ITS2 region) based on cultured material collected during 2010-2021. Statistical analyses of morphometric measurements may be used to differentiate some species if a sufficiently large number of cells are examined. Gambierdiscus vietnamensis sp. nov. is morphologically similar to other strongly reticulated species, such as G. belizeanus and possibly G. pacificus; the latter species is morphologically indistinguishable from G. vietnamensis sp. nov., but they are genetically distinct, and molecular analysis is deemed necessary for proper identification of the new species. This study also revealed that strains denoted G. pacificus from Hainan Island (China) should be included in G. vietnamensis sp. nov.

Abundance and sources of plastic debris on beaches in a plastic hotspot, Nha Trang, Viet Nam.

Viet Nam is challenged by extensive marine plastic pollution, however, remediation efforts are hampered by undefined sources to the coastal environment. This study surveyed the abundance, type, and source of beached plastic litter at seven beaches along the coast of Nha Trang, Viet Nam. A total of 4754 beached plastic litter items (>2 cm) yielded a mean abundance of 19.8 ± 19.5 items m-2 corresponding to 116 ± 226 g DW m-2. Our results demonstrate that plastic litter related to fishing and aquaculture constituted at least 62 % of the total by weight and 38 % by number, showing that these two sectors are responsible for a significant part of the plastic pollution along the coast. Hence, we argue that improved management of the fishing and aquaculture sectors could substantially reduce marine plastic pollution along Viet Nam's coast.

Diversity of Silica-Scaled Chrysophytes of Two Tropical Islands: Phu Quoc and Con Son (Viet Nam).

The present paper focuses on the silica-scaled chrysophytes from two tropical islands: Con Son (Con Dao Archipelago) and Phu Quoc, located in Viet Nam. Electron microscopy revealed fifty-seven taxa, of which forty-one belong to the genus Mallomonas. The others are species of the genera Synura (5), Paraphysomonas (8), Spiniferomonas (1), Chrysosphaerella (1) and Lepidochromonas (1). This is the first report of the genus Lepidochromonas from Viet Nam. In addition, two species from the genus Paraphysomonas are reported for the first time in the country. Six taxa from the genus Mallomonas and five taxa from the genus Paraphysomonas were not identifiable to the lower rank and may represent new species for science. The overall diversity of the silica-scaled chrysophytes of the islands is very high. A number of rare taxa endemic to Southeast Asia were found.

Suicide risk and mental health in the general population of French Polynesia.

OBJECTIVE: There are no reports on the burden of suicidal ideation and suicide attempts in the general population of French Polynesia (FP). We aimed to improve suicide prevention and mental health care by assessing the prevalence of suicide risk and major mental health disorders and care among adults in FP. METHODS: We conducted the Mental Health in General Population Survey in FP during 2015 to 2017. Participants were selected using the quota method to obtain a representative sample of the general population. Suicide risk and psychiatric diagnoses were assessed using the Mini International Neuropsychiatric Interview. RESULTS: We included 968 people aged 18 years or older. The prevalence of current suicidal ideation (13.1%) and current (2.6%) and lifetime suicide attempts (18.6%), as well as mental health disorders (42.8%), was high in FP. A notable proportion of participants with these conditions did not seek medical assistance. CONCLUSION: A high prevalence of suicide risk and mental health disorders was found in the general population of FP. Suicide prevention and mental health plans are needed in FP that include better access to primary care for the diagnosis and treatment of mental health disorders. Further research is needed to clarify cultural risk and protective factors.

Factors regulating growth pattern and condition factor of an amphibious fish Periophthalmus gracilis living in the Mekong Delta.

Growth pattern and condition factor (CF) are essential to fish resource assessment but limited to Periophthalmus gracilis-an amphibious fish living in the mudflats along the Indo-Pacific regions, including the Mekong Delta (MD), Vietnam. This study lasted from April 2020 to March 2021 to verify if their growth pattern and CF change with sex, size, season, month and site. The total length and weight of 486 individuals (236 females and 250 males) were 2.9-5.9 cm and 0.13-1.66 g, respectively. The mudskipper displayed negative allometry as the slope value (b = 2.69 ± 0.06) obtained from length and weight (LWR) was significantly less than 3 (p < 0.01), indicating that most fish specimens were caught in the immature stage. The fish growth pattern did not change with sex as both males and females displayed negative allometry but varied by size since the mudskipper showed negative allometry in the immature group and isometry in the mature group. Likewise, growth type changed with season since fish showed negative allometry in the dry season but isometry in the wet season. As the slope value (b) varied by site and month, the mudskipper displayed spatiotemporal growth patterns, ranging from negative to positive allometry. The CF was impacted by sex as this value of females (1.09 ± 0.02) was higher than that of males (0.96 ± 0.01, p < 0.01). Besides, CF was regulated by fish length since this value was higher in the mature group (1.12 ± 0.03) than in the immature group (1.01 ± 0.01, p < 0.01). Likewise, CF was affected by season as this value was higher in the wet season (1.05 ± 0.02) than in the dry season (0.99 ± 0.01, p < 0.01). Although the CF varied with site and month variables (p < 0.01), this value (1.02 ± 0.01) was generally higher than 1, showing fish adapted well to their habitat. The fish length at first capture should be increased to exploit this species sustainably.

Bacterial Composition Associated With Giant Colonies of the Harmful Algal Species Phaeocystis globosa.

The cosmopolitan algae Phaeocystis globosa forms harmful algal blooms frequently in a number of tropical and subtropical coastal regions in the past two decades. During the bloom, the giant colony, which is formed by P. globosa, is the dominant morphotype. However, the microenvironment and the microbial composition in the intracolonial fluid are poorly understood. Here, we used high-throughput 16S rRNA amplicon sequencing to examine the bacterial composition and predicted functions in intracolonial fluid. Compared with the bacterial consortia in ambient seawater, intracolonial fluids possessed the lower levels of microbial richness and diversity, implying selectivity of bacteria by the unique intracolonial microenvironment enclosed within the P. globosa polysaccharide envelope. The bacterial consortia in intracolonial fluid were dominated by Balneola (48.6% of total abundance) and Labrezia (28.5%). The bacteria and microbial function enriched in intracolonial fluid were involved in aromatic benzenoid compounds degradation, DMSP and DMS production and consumption, and antibacterial compounds synthesis. We suggest that the P. globosa colonial envelope allows for the formation of a specific microenvironment; thus, the unique microbial consortia inhabiting intracolonial fluid has close interaction with P. globosa cells, which may benefit colony development.

Comparing the performance of machine learning algorithms for remote and in situ estimations of chlorophyll-a content: A case study in the Tri An Reservoir, Vietnam.

Chlorophyll-a (Chl-a) is one of the most important indicators of the trophic status of inland waters, and its continued monitoring is essential. Recently, the operated Sentinel-2 MSI satellite offers high spatial resolution images for remote water quality monitoring. In this study, we tested the performance of the three well-known machine learning (ML) (random forest [RF], support vector machine [SVM], and Gaussian process [GP]) and the two novel ML (extreme gradient boost (XGB) and CatBoost [CB]) models for estimation a wide range of Chl-a concentration (10.1-798.7 µg/L) using the Sentinel-2 MSI data and in situ water quality measurement in the Tri An Reservoir (TAR), Vietnam. GP indicated the most reliable model for predicting Chl-a from water quality parameters (R2 = 0.85, root-mean-square error [RMSE] = 56.65 µg/L, Akaike's information criterion [AIC] = 575.10, and Bayesian information criterion [BIC] = 595.24). Regarding input model as water surface reflectance, CB was the superior model for Chl-a retrieval (R2 = 0.84, RMSE = 46.28 µg/L, AIC = 229.18, and BIC = 238.50). Our results indicated that GP and CB are the two best models for the prediction of Chl-a in TAR. Overall, the Sentinel-2 MSI coupled with ML algorithms is a reliable, inexpensive, and accurate instrument for monitoring Chl-a in inland waters. PRACTITIONER POINTS: Machine learning algorithms were used for both remote sensing data and in situ water quality measurements. The performance of five well-known machine learning models was tested Gaussian process was the most reliable model for predicting Chl-a from water quality parameters CatBoost was the best model for Chl-a retrieval from water surface reflectance.

Morphological and genetic analyses of Ostreopsis (Dinophyceae, Gonyaulacales, Ostreopsidaceae) species from Vietnamese waters with a re-description of the type species, O. siamensis.

Identification of species of the dinoflagellate genus Ostreopsis is difficult because several species have been poorly described, others misidentified in the literature, and the type species, O. siamensis, has not been described by contemporary taxonomic methods. In the present study, it is argued that Ostreopsis sp. 6 as described by previous authors is similar to the type species, and we offer an emended description of O. siamensis by LM, SEM, and molecular analyses of nuclear LSU and ITS rDNA based on material collected a few hundred kilometers from the type locality in the Gulf of Thailand and along the Vietnamese east coast. Ostreopsis siamensis is genetically different from the species reported as O. cf. siamensis in the literature and the latter should be described as a separate species. It is also concluded that with the poor knowledge of the morphological variability of many species of Ostreopsis, O. siamensis may not be distinguished from other similar-sized species by its morphological features, and hence molecular data are needed for reliable identification. The species Ostreopsis lenticularis and Ostreopsis cf. ovata were also found and described.

Supportive effect of body contact care with ylang ylang aromatherapy and mobile intervention team for suicide prevention: A pilot study.

OBJECTIVES: To assess understudied, alternative suicide prevention modalities in a mental health care setting. METHODS: This was a prospective study of patients (n = 140, 68 cases and 72 controls) who were admitted to hospital or who contacted an SOS suicide crisis line for suicidal ideation or attempts. Psychiatric diagnoses (Mini-International Neuropsychiatric Interview) and intensity of anxiety/depression/suicidality (Hamilton Anxiety Rating Scale, Montgomery-Åsberg Depression Rating Scale, and Beck Scale for Suicidal Ideation) were assessed. All intervention group subjects received a crisis card with a crisis line number, interviews with psychologists or volunteers and a telephone call on days 10 to 21, then 6 months later. These subjects also had a choice between two further 4-month interventions: body contact care or mobile intervention team visits. RESULTS: The interventions significantly reduced the number of suicide attempts and suicide (3%) at 6 months compared with the control condition (12%). There were fewer losses to follow-up in the intervention group (7.35%) than in the control group (9.72%). CONCLUSIONS: The results favour the implementation of integrated care and maintaining contact in suicide prevention.

Proximal Junctional Kyphosis: Inter- and Intraobserver Reliability of Radiographic Measurements in Adult Spinal Deformity.

STUDY DESIGN: Reliability study of radiographic measures of proximal junctional kyphosis (PJK) in patients with adult spinal deformity (ASD). OBJECTIVE: To assess impacts of level of proximal endpoint and vertebral fracture on reliability of measurement of junctional kyphosis. SUMMARY OF BACKGROUND DATA: Radiographic assessment is important in determining management of patients with PJK or proximal junctional failure (PJF). No study to date has evaluated the reliability of radiographic measurement of the junctional kyphotic angle after surgery for ASD. METHODS: Postoperative radiographs from 52 patients with ASD were divided into four categories based on the level of the upper instrumented vertebra (UIV) and the presence or absence of PJF: upper thoracic without failure (UT), thoracolumbar without failure (TL), upper thoracic with PJF (UTF), and thoracolumbar with PJF (TLF). Nine surgeon reviewers performed radiographic measurements of kyphosis between UIV+2 and UIV twice at least 4 weeks apart. Intraclass correlation coefficients (ICC) were calculated to determine inter- and intraobserver reliability. RESULTS: Interobserver reliability for measurements of UT, TL, UTF, and TLF were all "almost perfect" with ICC scores of 0.917, 0.965, 0.956, and 0.882, and 0.932, 0.975, 0958, and 0.989, for sessions 1 and 2, respectively. Similarly, ICCs for kyphosis measurements for the TL and TLF group had "almost perfect" agreement with means of 0.898 (range: 0.817-0.969) and 0.976 (range: 0.931-0.995), respectively. ICCs for measurements for the UT and UTF groups all had "substantial" or "almost perfect" agreement with means of 0.801 (range: 0.662-0.942) and 0.879 (range: 0.760-0.988), respectively. CONCLUSION: The present study demonstrates high inter- and intraobserver reliability of PJK measurement following instrumented fusion for ASD, independent of the presence or absence of PJF. Although slightly lower for upper thoracic than for thoracolumbar proximal endpoints, all ICCs consistently reached at least "substantial agreement" and "near perfect agreement" for most. LEVEL OF EVIDENCE: 4.

Toxicity screening of 13 Gambierdiscus strains using neuro-2a and erythrocyte lysis bioassays.

Species in the epi-benthic dinoflagellate genus Gambierdiscus produce ciguatoxins (CTXs) and maitotoxins (MTXs), which are among the most potent marine toxins known. Consumption of fish contaminated with sufficient quantities of CTXs causes Ciguatera Fish Poisoning (CFP), the largest cause of non-bacterial food poisoning worldwide. Maitotoxins, which can be found in the digestive system of fish, could also contribute to CFP if such tissues are consumed. Recently, an increasing number of Gambierdiscus species have been identified; yet, little is known about the variation in toxicity among Gambierdiscus strains or species. This study is the first assessment of relative CTX- and MTX-toxicity of Gambierdiscus species from areas as widespread as the North-Eastern Atlantic Ocean, Pacific Ocean and the Mediterranean Sea. A total of 13 strains were screened: (i) seven Pacific strains of G. australes, G. balechii, G. caribaeus, G. carpenteri, G. pacificus, G. scabrosus and one strain of an undetermined species (Gambierdiscus sp. Viet Nam), (ii) five strains from the North-Eastern Atlantic Ocean (two G. australes, a single G. excentricus and two G. silvae strains), and (iii) one G. carolinianus strain from the Mediterranean Sea. Cell pellets of Gambierdiscus were extracted with methanol and the crude extracts partitioned into a CTX-containing dichloromethane fraction and a MTX-containing aqueous methanol fraction. CTX-toxicity was estimated using the neuro-2a cytoxicity assay, and MTX-toxicity via a human erythrocyte lysis assay. Different species were grouped into different ratios of CTX- and MTX-toxicity, however, the ratio was not related to the geographical origin of species (Atlantic, Mediterranean, Pacific). All strains showed MTX-toxicity, ranging from 1.5 to 86pg MTX equivalents (eq) cell-1. All but one of the strains showed relatively low CTX-toxicity ranging from 0.6 to 50 fg CTX3C eq cell-1. The exception was the highly toxic G. excentricus strain from the Canary Islands, which produced 1426 fg CTX3C eq cell-1. As was true for CTX, the highest MTX-toxicity was also found in G. excentricus. Thus, the present study confirmed that at least one species from the Atlantic Ocean demonstrates similar toxicity as the most toxic strains from the Pacific, even if the metabolites in fish have so far been shown to be more toxic in the Pacific Ocean.

Proximal junctional kyphosis and failure-diagnosis, prevention, and treatment.

Technical advancements have enabled the spinal deformity surgeon to correct severe spinal mal-alignment. However, proximal adjacent segment pathology (ASP) remains a significant issue. Examples include proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). Agreement on the definition, classification, and pathophysiology of PJK and PJF remains incomplete, and an understanding of the risk factors, means of prevention, and treatment of this problem remains to be elucidated. In general, PJK is a relatively asymptomatic radiographic diagnosis managed with patient reassurance and monitoring. On the other hand, PJF is characterized by mechanical instability, pain, and more severe kyphosis, with potential for neurologic compromise. Patients who develop PJF more often require revision surgery than those with PJK. This chapter will review the current understanding of PJK and PJF.

Is Cervical Sagittal Imbalance a Risk Factor for Adjacent Segment Pathomechanics After Multilevel Fusion?

STUDY DESIGN: A biomechanical study using human spine specimens. OBJECTIVE: The aim of this study was to assess whether the presence of cervical sagittal imbalance is an independent risk factor for increasing the mechanical burden on discs adjacent to cervical multilevel fusions. SUMMARY OF BACKGROUND DATA: The horizontal offset distance between the C2 plumbline and C7 vertebral body (C2-C7 Sagittal Vertical Axis (SVA)) or the angle made with vertical by a line connecting the C2 and C7 vertebral bodies (C2-C7 tilt angle) are used as radiographic measures to assess cervical sagittal balance. There is level III clinical evidence that sagittal imbalance caused by kyphotic fusions or global spinal sagittal malalignment may increase the risk of adjacent segment pathology. METHODS: Thirteen human cadaveric cervical spines (Occiput-T1; age: 50.6 years; range: 21-67) were tested first in the native intact state and then after instrumentation across C4-C6 to simulate in situ two-level fusion. Specimens were tested using a previously validated experimental model that allowed measurement of spinal response to prescribed imbalance. The effects of fusion on segmental angular alignments and intradiscal pressures in the C3-C4 and C6-C7 discs, above and below the fusion, were evaluated at different magnitudes of C2-C7 tilt angle (or C2-C7 SVA). RESULTS: When compared with the pre-fusion state, in situ fusion across C4-C6 segments required increased flexion angulation and resulted in increased intradiscal pressure at the C6-C7 disc below the fusion in order to accommodate the same increase in C2-C7 tilt angle or C2-C7 SVA (P < 0.05). The adjacent segment mechanical burden due to fusion became greater with increasing C2-C7 tilt angle or SVA. CONCLUSION: Cervical sagittal imbalance arising from regional and/or global spinal sagittal malalignment may play a role in exacerbating adjacent segment pathomechanics after multilevel fusion and should be considered during surgical planning. LEVEL OF EVIDENCE: N/A.

Testing Brief Intervention and Phone Contact among Subjects with Suicidal Behavior: A Randomized Controlled Trial in French Polynesia in the Frames of the World Health Organization/Suicide Trends in At-Risk Territories Study.

The World Health Organization Suicide trends in at-risk territories study is a multi-site regional research program operating first in French Polynesia and countries of the Western Pacific, then extended to the world. The aims of the study were to establish a monitoring system for suicidal behaviors and to conduct a randomised control trial intervention for non-fatal suicidal behaviors. The latter part is the purpose of the present article. Over the period 2008-2010, 515 patients were admitted at the Emergency Department of the Centre Hospitalier de Polynésie Française for suicidal behavior. Those then hospitalized in the Psychiatry Emergency Unit were asked to be involved in the study and randomly allocated to either Treatment As Usual (TAU) or TAU plus Brief Intervention and Contact (BIC), which provides a psycho-education session and a follow-up of 9 phone contacts over an 18-months period. One hundred persons were assigned to TAU, while 100 participants were allocated to the BIC group. At the end of the follow-up there were no significant differences between the two groups in terms of number of presentations to the hospital for repeated suicidal behaviors. Although the study could not demonstrate the superiority of a treatment over the other, nevertheless - given its importance - the investigation captured public attention and was able to contribute to the awareness of the need of suicide prevention in French Polynesia. The BIC model of intervention seemed to particularly suit the geographical and health care context of the country.

Coral Mucus Is a Hot Spot for Viral Infections.

There is increasing suspicion that viral communities play a pivotal role in maintaining coral health, yet their main ecological traits still remain poorly characterized. In this study, we examined the seasonal distribution and reproduction pathways of viruses inhabiting the mucus of the scleractinians Fungia repanda and Acropora formosa collected in Nha Trang Bay (Vietnam) during an 11-month survey. The strong coupling between epibiotic viral and bacterial abundance suggested that phages are dominant among coral-associated viral communities. Mucosal viruses also exhibited significant differences in their main features between the two coral species and were also remarkably contrasted with their planktonic counterparts. For example, their abundance (inferred from epifluorescence counts), lytic production rates (KCN incubations), and the proportion of lysogenic cells (mitomycin C inductions) were, respectively, 2.6-, 9.5-, and 2.2-fold higher in mucus than in the surrounding water. Both lytic and lysogenic indicators were tightly coupled with temperature and salinity, suggesting that the life strategy of viral epibionts is strongly dependent upon environmental circumstances. Finally, our results suggest that coral mucus may represent a highly favorable habitat for viral proliferation, promoting the development of both temperate and virulent phages. Here, we discuss how such an optimized viral arsenal could be crucial for coral viability by presumably forging complex links with both symbiotic and adjacent nonsymbiotic microorganisms.

Postural Consequences of Cervical Sagittal Imbalance: A Novel Laboratory Model.

STUDY DESIGN: A biomechanical study using human spine specimens. OBJECTIVE: To study postural compensations in lordosis angles that are necessary to maintain horizontal gaze in the presence of forward head posture and increasing T1 sagittal tilt. SUMMARY OF BACKGROUND DATA: Forward head posture relative to the shoulders, assessed radiographically using the horizontal offset distance between the C2 and C7 vertebral bodies (C2-C7 [sagittal vertical alignment] SVA), is a measure of global cervical imbalance. This may result from kyphotic alignment of cervical segments, muscle imbalance, as well as malalignment of thoracolumbar spine. METHODS: Ten cadaveric cervical spines (occiput-T1) were tested. The T1 vertebra was anchored to a tilting and translating base. The occiput was free to move vertically but its angular orientation was constrained to ensure horizontal gaze regardless of sagittal imbalance. A 5-kg mass was attached to the occiput to mimic head weight. Forward head posture magnitude and T1 tilt were varied and motions of individual vertebrae were measured to calculate C2-C7 SVA and lordosis across C0-C2 and C2-C7. RESULTS: Increasing C2-C7 SVA caused flexion of lower cervical (C2-C7) segments and hyperextension of suboccipital (C0-C1-C2) segments to maintain horizontal gaze. Increasing kyphotic T1 tilt primarily increased lordosis across the C2-C7 segments. Regression models were developed to predict the compensatory C0-C2 and C2-C7 angulation needed to maintain horizontal gaze given values of C2-C7 SVA and T1 tilt. CONCLUSION: This study established predictive relationships between radiographical measures of forward head posture, T1 tilt, and postural compensations in the cervical lordosis angles needed to maintain horizontal gaze. The laboratory model predicted that normalization of C2-C7 SVA will reduce suboccipital (C0-C2) hyperextension, whereas T1 tilt reduction will reduce the hyperextension in the C2-C7 segments. The predictive relationships may help in planning corrective strategy in patients experiencing neck pain, which may be attributed to sagittal malalignment. LEVEL OF EVIDENCE: N/A.

Effect of physiological loads on cortical and traditional pedicle screw fixation.

STUDY DESIGN: Human cadaveric biomechanical study. OBJECTIVE: To determine the fixation strength of laterally directed, cortical pedicle screws under physiological loads. SUMMARY OF BACKGROUND DATA: Lateral trajectory cortical pedicle screws have been described as a means of obtaining improved fixation while minimizing soft-tissue dissection during lumbar instrumentation. Biomechanical data have demonstrated equivalent strength in a quasi-static model; however, no biomechanical information is available comparing the fixation of cortical with traditional pedicle screws under cyclic physiological loads. METHODS: Seventeen vertebral levels (T11-L5) underwent quantitative computed tomography. On 1 side, a laterally directed, cortical pedicle screw was inserted with a traditional, medially directed pedicle screw placed on the contralateral side. With the specimen constrained in a testing apparatus, each screw underwent cyclic craniocaudal toggling under incrementally increasing physiological loads until 2 mm of head displacement occurred. Next, uniaxial pullout of each toggled screw was performed. The number of craniocaudal toggle cycles and load (N) required to achieve pedicle screw movement as well as axial pullout resistance (N) were compared between the 2 techniques. RESULTS: The mean trabecular bone mineral density of the specimens was 202 K2HPO4 mg/cm. Cortical pedicle screws demonstrated significantly improved resistance to toggle testing, requiring 184 cycles to reach 2 mm of displacement compared with 102 cycles for the traditional pedicle screws (P=0.002). The force necessary to displace the screws was also significantly greater for the cortical versus the traditional screws (398 N vs. 300 N, P=0.004). There was no statistical difference in axial pullout strength between the previously toggled cortical and traditional pedicle screws (1722 N vs. 1741 N, P=0.837). CONCLUSION: Laterally directed cortical pedicle screws have superior resistance to craniocaudal toggling compared with traditional pedicle screws. LEVEL OF EVIDENCE: N/A.

High occurrence of viruses in the mucus layer of scleractinian corals.

Viruses attract increasing interest from environmental microbiologists seeking to understand their function and role in coral health. However, little is known about their main ecological traits within the coral holobiont. In this study, a quantitative and qualitative characterization of viral and bacterial communities was conducted on the mucus of seven different coral species of the Van Phong Bay (Vietnam). On average, the concentrations of viruses and bacteria were, respectively, 17- and twofold higher in the mucus than in the surrounding water. The examination of bacterial community composition also showed remarkable differences between mucus and water samples. The percentage of active respiring cells was nearly threefold higher in mucus (m = 24.8%) than in water (m = 8.6%). Interestingly, a positive and highly significant correlation was observed between the proportion of active cells and viral abundance in the mucus, suggesting that the metabolism of the bacterial associates is probably a strong determinant of the distribution of viruses within the coral holobiont. Overall, coral mucus, given its unique physicochemical characteristics and sticking properties, can be regarded as a highly selective biotope for abundant, diversified and specialized symbiotic microbial and viral organisms.

Characteristic profiles of Ciguatera toxins in different strains of Gambierdiscus spp.

Ciguatera fish poisoning characterizes the intoxication caused by consumption of fish from tropical and subtropical areas, which have accumulated ciguatoxins (CTXs). The observed pattern of ciguatoxins in fish highly depends on the marine region and the causative organisms. It is evident that differences exist between ciguatoxins produced by certain strains of the dinoflagellate Gambierdiscus toxicus and other Gambierdiscus spp. In this context cultured strains purchased from the Provasoli-Guillard National Center for Culture of Marine Phytoplankton (CCMP) and strains from Vietnam were analyzed. Besides, lyophilized samples of several Gambierdiscus spp. from the National Oceanic and Atmospheric Administration (NOAA), USA and lyophilized samples of G. toxicus from Vietnam were analyzed. The latter has been cultured at different salinities. We observed differences between the toxin ratios of the analogues in the strain from Vietnam depending on the salinity. The CTX profiles of the Vietnamese samples were compared with cultures of Gambierdiscus spp. from CCMP and the National Oceanic and Atmospheric Administration (NOAA) resulting in an overview of toxins in cultures from different regions. Hence, it was obvious that the strain from Vietnam forms a characteristic CTX profile which is not directly comparable to CTX pattern observed in other tropical marine regions.

Prevalence of chronic symptoms of ciguatera disease in French Polynesian adults.

Ciguatera is a tropical disease caused by seafood poisoning, for which the duration of symptoms remains to be determined. The objectives of this prospective study were to determine the prevalence of symptoms at different time points and to identify factors associated with chronic symptoms observed in adults suffering from this disease. At the time of onset, we observed a dose-response relationship including a strong association between the delay of appearance of symptoms and a severity index (P < 0.001). Our results confirmed the key role of fish organs in the risk of contracting a more severe form of ciguatera. In the chronic stage, only the severity score based on information recorded in the acute phase is related to the persistence of symptoms (P < 0.001). Our findings suggest that several symptoms observed in the acute phase of the disease are still experienced 15 days after onset. This supports previous observations based on isolated case reports.