15 research outputs found
Molecular Identification of Gambierdiscus and Fukuyoa (Dinophyceae) from Environmental Samples.
Ciguatera Fish Poisoning (CFP) is increasing across the Pacific and the distribution of the causative dinoflagellates appears to be expanding. Subtle differences in thecal plate morphology are used to distinguish dinoflagellate species, which are difficult to determine using light microscopy. For these reasons we sought to develop a Quantitative PCR assay that would detect all species from both Gambierdiscus and Fukuyoa genera in order to rapidly screen environmental samples for potentially toxic species. Additionally, a specific assay for F. paulensis was developed as this species is of concern in New Zealand coastal waters. Using the assays we analyzed 31 samples from three locations around New Zealand and the Kingdom of Tonga. Fourteen samples in total were positive for Gambierdiscus/Fukuyoa and two samples were also positive using the F. paulensis assay. Samples from the Kermadec Islands were further characterized using high-throughput sequencing metabarcoding. The majority of reads corresponded to Gambierdiscus species with three species identified at all sites (G. australes, G. honu and G. polynesiensis). This is the first confirmed identification of G. polynesiensis, a known ciguatoxin producer, in New Zealand waters. Other known toxin-producing genera were also detected, included Alexandrium, Amphidinium, Azadinium, Dinophysis, Ostreopsis, and Prorocentrum
Standardization of kinetic determination of nitrite based on its catalytic effect on an indicator reaction
A catalytic kinetic procedure for nitrite determination based on its catalytic effect on the oxidation of brilliant cresyl blue (BCB) by bromate ion in acidic media is standardized and proposed. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of BCB at its λmax 595nm. The calibration
graph is linear from 1-80 ng.mlâ1 of nitrite. The detection limit is 5.8 ng.mlâ1 of nitrite. Nitrite in the range of 10â80 ng.mLâ1 has been determined successfully where recoveries were 97.3 ⌠103.7% with the relative standard deviation 0.1 ⌠0.8%. The effect of many foreign ions upon determination of 70 ng.mLâ1 of nitrite has been studied and shown that most common cations and anions do not interfere in the determination except Fe2+ which was masked. The
procedure was successfully applied for the determination of nitrite in wastewater and seawater with satisfactory results. The typical feature of this procedure is that the determination could be carried at normal temperature of 25ÂșC with analysis time of 4 min
Development and validation of catalytic kinetic spectrophotometric method for determination of copper(II)
enspA catalytic kinetic spectrophotometric method is developed for the determination of trace amounts of Cu(II). It is based on the catalytic effect of Cu(II) on the oxidation of cysteine (RSH) by hexacyanoferrate(III) in acidic medium. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of hexacyanoferrate(III) at 420thinspnm. The optimum operating conditions regarding concentration of reagents, pH and temperature were established. The working curve is linear in the concentration range of 0â6.35thinspngâąmLâ1. The maximum percentage error and standard deviation for determination of Cu(II) in the range of 1.27â6.35thinspngâąmLâ1 have been calculated to be 3.9 and 0.4 respectively. The detection limit calculated was 0.15thinspngâąmLâ1. The interference effect of several species was also investigated, and it was found that the most common cations and anions do not interfere with the determination. The developed procedure was successfully applied to the determination of Cu(II) in various synthetic and real samples. The typical feature of this procedure is that determination can be carried out at 25thinsp°C and/or in the absence of any precision thermostatic bath in the very short analysis time of one minute. The newly developed method was found to have fairly good selectivity, sensitivity, simplicity and rapidity compared to other kinetic methods
Molecular identification of Gambierdiscus and Fukuyoa (Dinophyceae) from environmental samples
© 2017 by the authors. Licensee MDPI. Ciguatera Fish Poisoning (CFP) is increasing across the Pacific and the distribution of the causative dinoflagellates appears to be expanding. Subtle differences in thecal plate morphology are used to distinguish dinoflagellate species, which are difficult to determine using light microscopy. For these reasons we sought to develop a Quantitative PCR assay that would detect all species from both Gambierdiscus and Fukuyoa genera in order to rapidly screen environmental samples for potentially toxic species. Additionally, a specific assay for F. paulensis was developed as this species is of concern in New Zealand coastal waters. Using the assays we analyzed 31 samples from three locations around New Zealand and the Kingdom of Tonga. Fourteen samples in total were positive for Gambierdiscus/Fukuyoa and two samples were also positive using the F. paulensis assay. Samples from the Kermadec Islands were further characterized using high-throughput sequencing metabarcoding. The majority of reads corresponded to Gambierdiscus species with three species identified at all sites (G. australes, G. honu and G. polynesiensis). This is the first confirmed identification of G. polynesiensis, a known ciguatoxin producer, in New Zealand waters. Other known toxin-producing genera were also detected, included Alexandrium, Amphidinium, Azadinium, Dinophysis, Ostreopsis, and Prorocentrum
High intra-ocean, but limited inter-ocean genetic connectivity in populations of the deep-water oblique-banded snapper Pristipomoides zonatus (Pisces: Lutjanidae)
While many studies have investigated connectivity and subdivision in marine fish occupying tropical, shallow water reef habitats, relatively few have been conducted on commercially important deep-water species in the Indo-Pacific region. Here, we examine spatial and temporal genetic variation in the deep-water oblique-banded snapper Pristipomoides zonatus, collected from eight locations across the Indian and Pacific Oceans. A total of 292 individuals were screened for genetic variation at six nuclear microsatellite loci and the cytochrome c oxidase subunit 1 (COI) mitochondrial DNA (mtDNA) gene. There was evidence of low, but significant genetic differentiation between ocean basins (FCTÂ =Â 0.009) and no significant divergences between sites within oceans. The lack of population structure within ocean basins suggests P. zonatus has a long pelagic larval duration with high levels of connectivity between populations over large geographical distances (>2000Â km). There was no evidence of temporal variation in allele frequencies within populations. However, ephemeral genetic divergences between sites were detected, along with a significant reduction in genetic diversity at one site, suggesting there may be low effective population sizes (Ne). Our results suggest that localized declines in genetic diversity could be offset by gene flow from other locations within ocean basins, though predicting the broader impacts of localized stock depletions requires further understanding of recruitment dynamics and life history characteristics of the species
Oceanic, latitudinal and sex-specific variation in demography of a tropical deepwater snapper across the Indo-Pacific region
Deepwater tropical fisheries provide an important source of income and protein to Pacific
and Indian Ocean coastal communities who are highly dependent on fish for food
security. The development of quantitative assessments and management strategies for
these deepwater fisheries has been hindered by insufficient biological and fisheries data.
We examine the age-specific demography of the pygmy ruby snapper Etelis carbunculus,
an important target species in tropical deepwater fisheries, across 90⊠of longitude
and 20⊠of latitude in the Pacific and Indian Oceans. Our results show that growth of
E. carbunculus varies significantly between oceans and sexes and across latitudes in
both oceans. Estimates of natural and fishing mortality were similar between oceans, but
higher for females than males in both oceans. Evidence of greater fishing pressure on
females than males is likely due to the larger size-at-age of females compared to males,
assuming that selectivity of the fishing gear is related directly to fish size. Sex ratios were
significantly female biased in both oceans despite this species being gonochoristic, and
maturity schedules were similar between sexes in the Pacific Ocean. This species exhibits
a protracted spawning season from mid-spring to autumn (i.e., October to May) in the
Pacific Ocean. These results represent the first estimates of age-specific demographic
parameters for E. carbunculus, and provide the foundation for the development of the
first species-specific assessment models and harvest strategies for the species. Future
stock assessment models for E. carbunculus should consider sex-specific demographic
parameters and spatial variation in demography. Our results reveal substantial differences
in biology between E. carbunculus and the giant ruby snapper E. sp., a cryptic congeneric
species, and thus contribute to greater clarity in managing fisheries that are dependent
on these two species. Furthermore, the improved information on the life history of
E. carbunculus contributes to the broader sustainable management and improved food
security for deepwater snapper fisheries in the Indo-Pacific region
Coral reef annihilation, persistence and recovery at Earth's youngest volcanic island
The structure and function of coral reef ecosystems is increasingly compromised by multiple stressors, even in the most remote locations. Severe, acute disturbances such as volcanic eruptions represent extreme events that can annihilate entire reef ecosystems, but also provide unique opportunities to examine ecosystem resilience and recovery. Here, we examine the destruction, persistence and initial recovery of reefs associated with the hydro-magmatic eruption that created Earth's newest landmass, the Hunga Tonga-Hunga Ha'apai volcanic island. Despite extreme conditions associated with the eruption, impacts on nearby reefs were spatially variable. Importantly, even heavily affected reefs showed signs of rapid recovery driven by high recruitment, likely from local refuges. The remote location and corresponding lack of additional stressors likely contribute to the resilience of Hunga's reefs, suggesting that in the absence of chronic anthropogenic stressors, coral reefs can be resilient to one of the largest physical disturbances on Earth
Coral reef annihilation, persistence and recovery at Earthâs youngest volcanic island
The structure and function of coral reef ecosystems is increasingly compromised by multiple stressors, even in the most remote locations. Severe, acute disturbances such as volcanic eruptions represent extreme events that can annihilate entire reef ecosystems, but also provide unique opportunities to examine ecosystem resilience and recovery. Here, we examine the destruction, persistence and initial recovery of reefs associated with the hydro-magmatic eruption that created Earthâs newest landmass, the Hunga TongaâHunga Haâapai volcanic island. Despite extreme conditions associated with the eruption, impacts on nearby reefs were spatially variable. Importantly, even heavily affected reefs showed signs of rapid recovery driven by high recruitment, likely from local refuges. The remote location and corresponding lack of additional stressors likely contribute to the resilience of Hungaâs reefs, suggesting that in the absence of chronic anthropogenic stressors, coral reefs can be resilient to one of the largest physical disturbances on Earth
Ageing bias and precision for deep-water snappers: evaluating nascent otolith preparation methods using novel multivariate comparisons among readers and growth parameter estimates
Tropical deep-water snappers (Etelinae) support valuable fisheries across the Indo-Pacific, with stock assessments reliant on age-based information in the absence of reliable catch and effort statistics. These long-lived species have been considered notoriously difficult to age. However, nascent developments in ageing protocols, particularly thinner transverse sections of otoliths ( 180â200 mm), are providing improvements in growth zone clarity, interpretation and repeatability of annuli counts. At a recent international workshop, thin sectioned otoliths from three deep-water snappers were read under reflected light by eight fisheries scientists from across the Indo-Pacific, with various levels of fish-ageing experience. Precision and bias were assessed using traditional ageing precision metrics (index of average percent error, IAPE; and coefficient of variation, CV), and a novel approach using multivariate analyses (metric multidimensional scaling, mMDS) based on Euclidean dissimilarity among readersâ counts and subsequent von Bertalanffy (vB) growth parameter estimates. Annuli counts between the primary reader and all other readers were within two for 80% of estimates, with uniform variation across a wide age range for Etelis carbunculus (intraclass correlation coefficient (ICC) ÂŒ 0.924, nÂŒ20, 3â25 annuli) and Etelis sp. (ICC ÂŒ 0.933, nÂŒ15, 2â27 annuli). In contrast, annuli counts for Pristipomoides filamentosus (nÂŒ14, 4â49) were less precise (i.e. ICC ÂŒ 0.835, 66% of counts within two of primary reader) with a bias toward greater variation in younger, pre-maturational life stages ( 5 annuli). Traditionally accepted ageing precision (IAPE 5.5%, CV 7.6%) was achieved for each species, but was commensurate with reader experience. The multivariate mMDS ordination was more informative in identifying both distance (i.e. dissimilarity) and direction (i.e. form) of variations in annuli counts and vB growth parameter estimates among readers. The acceptable level of ageing precision and bias achieved among most readers indicated that deep-water snappers can be aged precisely when appropriate otolith preparation methods are used. This study contributes towards ageing protocols that can be used to (i) interrogate bias and precision of age data for stock assessments, and (ii) standardise comparisons of age-based life history characteristics across a species range
Zampanolides BâE from the Marine Sponge Cacospongia mycofijiensis: Potent Cytotoxic Macrolides with Microtubule- Stabilizing Activity
Four new compounds (2â5) structurally
related to the microtubule-stabilizing agent (â)-zampanolide
(1) have been isolated from the Tongan marine sponge
Cacospongia mycofijiensis. Three of these new structures,
zampanolides BâD (2â4), exhibit nanomolar cytotoxicity
toward the HL-60 cell line, are antimitotic, and induce in vitro
tubulin polymerization at levels comparable to 1. Zampanolide
E (5), saturated at C-8/C-9, was significantly less potent
and does not stabilize purified tubulin, even at 10-fold higher
concentrations. The structural differences across these
compounds reveal a plasticity of the zampanolide pharmacophore.
While unsaturation is required at Î8, the configuration
of this alkene and those of Î4 and Î4âČ have little effect on
tubulin polymerization. The first natural co-occurrence of 1 and (â)-dactylolide (6) from the same sponge extract is also note