Increased prevalence of ubiquitous ascomycetes in an acropoid coral (Acropora formosa) exhibiting symptoms of Brown Band syndrome and skeletal eroding band disease

The prevalence of coral-associated fungi was four times higher in diseased Acropora formosa colonies than in healthy colonies. Since taxonomically related fungal species were isolated from diseased and healthy colonies, we suggest that their association with coral may be constitutive but that their abundance is dependent on coral health.     

Herbivorous fish assemblages and herbivory pressure on Laamu Atoll, Republic of Maldives

While herbivory is recognized as a fundamental process structuring coral reef communities, herbivore assemblages and processes are poorly described for reefs in the Indian Ocean region. We quantified herbivorous fish assemblage structure (abundance and diversity) in Laamu Atoll, Republic of Maldives, in four reef habitat types: faro reef flats, faro reef slopes, inner and outer atoll reef slopes (20 sites in total). Herbivorous fish assemblages, representing a total of 30 species, grouped strongly by habitat type, with the highest absolute abundance observed on faro reef flats and lowest abundance on inside atoll rim reef slopes. Removal of Thalassia seagrass blades by ambient herbivore assemblages was used in a bioassay to assess relative herbivory pressure among four habitat types (eight sites). Also, at one site a choice herbivory assay was performed to assess herbivore preference among four benthic plants across three depth zones. Relative herbivory, as indicated by Thalassia assays, was highest on inside atoll rim reef slopes and lowest on outside atoll rim reef slopes. Thalassia consumption did not correspond to overall herbivorous fish abundance, but corresponded more closely with parrotfish abundance. In the choice assays, herbivores showed strong preferences among plant types and consumption of most plant types was higher at mid-depth than in the shallow reef flat or deep reef knoll zones.     

Distribution, host range and large-scale spatial variability in black band disease prevalence on the Great Barrier Reef, Australia

The prevalence and host range of black band disease (BBD) was determined from surveys of 19 reefs within the Great Barrier Reef Marine Park, Australia. Prevalence of BBD was compared among reefs distributed across large-scale cross-shelf and long-shelf gradients of terrestrial or anthropogenic influence. We found that BBD was widespread throughout the Great Barrier Reef (GBR) and was present on 73.7% of the 19 reefs surveyed in 3 latitudinal sectors and 3 cross-shelf positions in the summer of 2004. Although BBD occurred on all mid-shelf reefs and all but one outer-shelf reefs, overall prevalence was low, infecting on average 0.09% of sessile cnidarians and 0.1% of scleractinian corals surveyed. BBD affected approximately 7% of scleractinian taxa (25 of approximately 350 GBR hard coral species) and 1 soft coral family, although most cases of BBD were recorded on branching Acropora species. Prevalence of BBD did not correlate with distance from terrestrial influences, being highest on mid-shelf reefs and lowest on inshore reefs (absent from 66%, n = 6, of these reefs). BBD prevalence was consistently higher in all shelf positions in the northern (Cooktown/Lizard Island) sector, which is adjacent to relatively pristine catchments compared to the central (Townsville) sector, which is adjacent to a more developed catchment. BBD cases were clustered within reefs and transects, which was consistent with local dispersal of pathogens via currents, although the spread of BBD was not dependent on the density or cover of any of the coral taxa examined. In combination, these results suggest that BBD is part of the natural ecology of coral assemblages of the GBR, and its prevalence is relatively unaffected by terrestrial influences on the scales characteristic of cross-shelf gradients.     

Epidemiology of skeletal eroding band on the Great Barrier Reef and the role of injury in the initiation of this widespread coral disease

Skeletal eroding band (SEB), which manifests as dense aggregations of the ciliate Halofolliculina corallasia, was the first coral disease described from the Indo-Pacific. Little is known about its etiology or impact. This study describes the distribution, prevalence and host range of SEB on a 500 km extent of the Great Barrier Reef (GBR), together with in situ rates of progression and infection following experimental injury. SEB occurred on 90–100% of reefs surveyed (n=18) in each of 3 years, demonstrating that SEB is widely distributed and persistent. SEB had the highest prevalence of any disease, affecting approximately 2% of 283,486 scleractinians and hydrocorals surveyed. Its host range was large, affecting 12 families and at least 82 scleractinian species, as well as the hydrocoral, Millepora. Corals in the families Pocilloporidae and Acroporidae were most susceptible, the former being up to five times more susceptible than other families. Progressive tissue loss was recorded on 95% of Acropora muricata colonies monitored (n = 18), with rates of SEB progression averaging ∼2 mm/day. Injury experiments demonstrated that H. corallasia, the putative pathogen of SEB, readily colonised recently exposed coral skeleton in the absence of a vector, but did not colonise intact coral tissue. Invading ciliates failed to form band-like aggregations associated with progressive tissue loss on any of three coral species tested experimentally, suggesting that, while H. corallasia readily colonises recently exposed coral skeleton, it may not be sufficient in itself to cause tissue mortality. Interactions with additional agents or factors, increasing ciliate virulence or lowering disease resistance of coral hosts may be required before halofolliculinid infections become associated with tissue loss.     

Spatial distribution and temporal variability of some aquatic insects in the Franco-Geneva River,Allondon

The Allodon River, a tributary of the Rhône, has suffered considerably from the recent expansion of human activities in the Geneva region. This study documents changes in its benthic fauna by comparing species richness before and after 1986 and by considering the possibilities of recolonization by drift.

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Résumé L'Allondon, affluent du Rhône, est une rivière qui a considérablemen t souffert d'une expansion récente des activités humaines dans la région genevoise. Cette étude met en lumière l'évolution de certains éléments de la faune benthique en comparant les richesses specifiques avant et après 1986, année critique pour la macrofaune benthique du bassin genevois. Elle met en évidence les possibilités de recolonisation par dérive de certains recours de l'Allondon à partir d'affluents moins perturbés.

     

Spatial variability in the distribution of dominant shallow-water benthos at Adelaide Island, Antarctica

Studies from temperate and tropical regions have shown that variability in the distribution of benthos exists at different spatial scales. There are very few similar studies from polar systems, the shallows of which represent some of the most intensely disturbed habitats on the planet. Variability in the abundances of the five most common macrofauna was examined at three spatial scales, metres, tens of metres and hundreds of metres, in the shallows (5-25 m depth) of Adelaide Island, West Antarctic Peninsula. Whilst significant community change occurs along a depth gradient at the study sites, not all of the common species studied showed clear depth-related patterns of distribution. Furthermore, although abundance patterns varied between the organisms, consistent depth-related trends in the spatial scale contributing most to the variability were observed for four of the five species. For four species the relative importance of large-scale variability (between sites) decreased from 5 to 25 m depth, whilst small-scale variability (between replicates) increased along the depth gradient. Variation between sites is probably largely driven by ice disturbance, which becomes less frequent with depth. Conversely, small-scale patchiness is promoted by biological interactions, which become relatively more influential as community complexity and species richness increase along the depth gradient.     

Crown-of-thorns starfish predation and physical injuries promote brown band disease on corals

Brown band (BrB) disease manifests on corals as a ciliate-dominated lesion that typically progresses rapidly causing extensive mortality, but it is unclear whether the dominant ciliate Porpostoma guamense is a primary or an opportunistic pathogen, the latter taking advantage of compromised coral tissue or depressed host resistance. In this study, manipulative aquarium-based experiments were used to investigate the role of P. guamense as a pathogen when inoculated onto fragments of the coral Acropora hyacinthus that were either healthy, preyed on by Acanthaster planci (crown-of-thorns starfish; COTS), or experimentally injured. Following ciliate inoculation, BrB lesions developed on all of COTS-predated fragments (n = 9 fragments) and progressed up to 4.6 ± 0.3 cm d^?1, resulting in ~70 % of coral tissue loss after 4 d. Similarly, BrB lesions developed rapidly on experimentally injured corals and ~38 % of coral tissue area was lost 60 h after inoculation. In contrast, no BrB lesions were observed on healthy corals following experimental inoculations. A choice experiment demonstrated that ciliates are strongly attracted to physically injured corals, with over 55 % of inoculated ciliates migrating to injured corals and forming distinct lesions, whereas ciliates did not migrate to healthy corals. Our results indicate that ciliates characteristic of BrB disease are opportunistic pathogens that rapidly migrate to and colonise compromised coral tissue, leading to rapid coral mortality, particularly following predation or injury. Predicted increases in tropical storms, cyclones, and COTS outbreaks are likely to increase the incidence of coral injury in the near future, promoting BrB disease and further contributing to declines in coral cover.     

Modern foraminiferal distribution and diversity in two atolls from the Maldives,Indian Ocean

Foraminifera from the coral-reef lagoons of two atolls are used to investigate the distribution and diversity of assemblages in the central Indian Ocean. Eight assemblages and 270 species of foraminifera are identified. Three assemblages are reefal and dominated by Amphistegina and Calcarina. Only one lagoon assemblage is present in both atolls, which is characterized by abundant Ammonia sp. 1 and smaller miliolid foraminifera. In Ari Atoll, abundant Amphistegina sp. 1, Operculina ammonoides, Amphistegina radiata and Nummulites venosa characterize one lagoon assemblage and abundant Neoeponides bradyi and Textularia cf. T. cushmani characterize the other. In Rasdhoo Atoll, abundant Textularia gr. foliacea and Spiroloculina nummiformis characterize one lagoon assemblage and abundant Textularia cf. T. cushmani and Textularia sp. 5 characterize the other. The assemblages compare well with sedimentological characteristics, which is also reflected in their distributions. Species diversity in the Maldives appears to be higher than the western Indian Ocean region due to the stronger influence of central Indo-Pacific faunas. It is not however, as high as the central Indo-Pacific region, which may be due to lower habitat diversity.     

Spatial and temporal variability of xylan distribution in differentiating secondary xylem of hybrid aspen

Xylans occupy approximately one-third of the cell wall components in hardwoods and their chemical structures are well understood. However, the microdistribution of xylans (O-acetyl-4-O-methylglucuronoxylans, AcGXs) in the cell wall and their correlation with functional properties of cells in hardwood xylem is poorly understood. We demonstrate here the spatial and temporal distribution of xylans in secondary xylem cells of hybrid aspen using immunolocalization with LM10 and LM11 antibodies. Xylan labeling was detected earliest in fibers at the cell corner of the S? layer, and then later in vessels and ray cells respectively. Fibers showed a heterogeneous labeling pattern in the mature cell wall with stronger labeling of low substituted xylans (lsAcGXs) in the outer than inner cell wall. In contrast, vessels showed uniform labeling in the mature cell wall with stronger labeling of lsAcGXs than fibers. Xylan labeling in ray cells was detected much later than that in fibers and vessels, but was also detected at the beginning of secondary cell wall formation as in fibers and vessels with uniform labeling in the cell wall regardless of developmental stage. Interestingly, pit membranes including fiber-, vessel- and ray-vessel pits showed strong labeling of highly substituted xylans (hsAcGXs) during differentiation, although this labeling gradually disappeared during pit maturation. Together our observations indicate that there are temporal and spatial variations of xylan deposition and chemical structure of xylans between cells in aspen xylem. Differences in xylan localization between aspen (hardwood) and cedar (softwood) are also discussed.     

Spatial Ca(2+) distribution in contracting skeletal and cardiac muscle cells

The spatiotemporal distribution of intracellular Ca(2+) release in contracting skeletal and cardiac muscle cells was defined using a snapshot imaging technique. Calcium imaging was performed on intact skeletal and cardiac muscle cells during contractions induced by an action potential (AP). The sarcomere length of the skeletal and cardiac cells was approximately 2 micrometer. Imaging Rhod-2 fluorescence only during a very brief (7 ns) snapshot of excitation light minimized potential image-blurring artifacts due to movement and/or diffusion. In skeletal muscle cells, the AP triggered a large fast Ca(2+) transient that peaked in less than 3 ms. Distinct subsarcomeric Ca(2+) gradients were evident during the first 4 ms of the skeletal Ca(2+) transient. In cardiac muscle, the AP-triggered Ca(2+) transient was much slower and peaked in approximately 100 ms. In contrast to the skeletal case, there were no detectable subsarcomeric Ca(2+) gradients during the cardiac Ca(2+) transient. Theoretical simulations suggest that the subsarcomeric Ca(2+) gradients seen in skeletal muscle were detectable because of the high speed and synchrony of local Ca(2+) release. Slower asynchronous recruitment of local Ca(2+) release units may account for the absence of detectable subsarcomeric Ca(2+) gradients in cardiac muscle. The speed and synchrony of local Ca(2+) gradients are quite different in AP-activated contracting cardiac and skeletal muscle cells at normal resting sarcomere lengths.     

Farming behaviour of reef fishes increases the prevalence of coral disease associated microbes and black band disease

Microbial community structure on coral reefs is strongly influenced by coral–algae interactions; however, the extent to which this influence is mediated by fishes is unknown. By excluding fleshy macroalgae, cultivating palatable filamentous algae and engaging in frequent aggression to protect resources, territorial damselfish (f. Pomacentridae), such as Stegastes, mediate macro-benthic dynamics on coral reefs and may significantly influence microbial communities. To elucidate how Stegastes apicalis and Stegastes nigricans may alter benthic microbial assemblages and coral health, we determined the benthic community composition (epilithic algal matrix and prokaryotes) and coral disease prevalence inside and outside of damselfish territories in the Great Barrier Reef, Australia. 16S rDNA sequencing revealed distinct bacterial communities associated with turf algae and a two to three times greater relative abundance of phylotypes with high sequence similarity to potential coral pathogens inside Stegastes''s territories. These potentially pathogenic phylotypes (totalling 30.04% of the community) were found to have high sequence similarity to those amplified from black band disease (BBD) and disease affected corals worldwide. Disease surveys further revealed a significantly higher occurrence of BBD inside S. nigricans''s territories. These findings demonstrate the first link between fish behaviour, reservoirs of potential coral disease pathogens and the prevalence of coral disease.     

Spatial and temporal patterns of scleractinian coral, soft coral, and zoanthid disease on a remote, near-pristine coral reef (Palmyra Atoll, central Pacific)

There is an urgent need for accurate baselines of coral disease prevalence across our oceans in order for sudden or unnatural changes to be recognized. Palmyra Atoll allows us to study disease dynamics under near-pristine, functionally intact conditions. We examined disease prevalence among all known species of scleractinian coral, soft coral and zoanthid (Palythoa) at a variety of coral reef habitats at Palmyra over a 2 yr period. In 2008, overall disease prevalence across the atoll was low (0.33%), but higher on the shallower backreef (0.88%) and reef terrace (0.80%) than on the deeper forereef (0.09%). Scleractinian coral disease prevalence was higher (0.30%) than were soft coral and zoanthid disease (0.03% combined). Growth anomalies (GAs) were the most commonly encountered lesions, with scleractinian species in the genera Astreopora (2.12%), Acropora (1.30%), and Montipora (0.98%) showing the highest prevalence atoll-wide. Discoloration necrosis (DN) was most prevalent in the zoanthid Palythoa tuberculosa (1.18%), although the soft coral Sinulana and Montipora also had a prevalence of 0.44 and 0.01%, respectively. Overall disease prevalence within permanently marked transects increased from 0.65% in 2008 to 0.79% in 2009. Palythoa DN contributed most to this increased prevalence, which coincided with rising temperatures during the 2009 El Ni?o. GAs on the majority of susceptible genera at Palmyra increased in number over time, and led to tissue death. Host distribution and environmental factors (e.g., temperature) appear to be important for determining spatiotemporal patterns of disease at Palmyra. More sophisticated analyses are required to tease apart the likely inter-correlated proximate drivers of disease occurrence on remote, near-pristine reefs.     

沿黄稻区灰飞虱越冬种群的时空分布及抽样技术研究

2009—2010年间系统调查了河南省境内沿黄稻区灰飞虱Laodelphax striatellus Fallén越冬种群的时空动态变化,并在田间调查的基础上,运用聚集度指标法和改进的Iwao回归分析法对沿黄稻区灰飞虱越冬种群的空间分布格局、理论抽样数及序贯抽样技术进行了研究。结果表明,灰飞虱在沿黄流域主要以少量3、4龄若虫进行越冬,11月下旬进入越冬期,翌年4月上中旬为越冬代种群发生高峰期,成、若虫虫量分别为22头/m2、43头/m2;灰飞虱成虫在5月中旬开始向水稻田迁飞,迁入高峰时虫量在450头/m2以上;灰飞虱越冬代成虫在麦田中空间分布型的聚集性指标大于1,空间分布型为聚集分布型,在此基础上得出灰飞虱田间调查的理论抽样数公式:N=t2/D2(0.324/m+0.086),并且描述了灰飞虱种群序贯抽样的Iwao模型:Tn=25n±15.4n~(1/2)。研究结果为田间灰飞虱的准确抽样调查和有效防治提供了科学依据。     

Spatial, seasonal and long-term variability of phytoplankton photosynthesis in lakes

A cross-system, worldwide approach has been used to ascertainthe spatial, seasonal and long-term variability of areal phytoplanktonphotosynthesis (PP) in lakes using published data sets. Also,the average fraction of annual PP occurring under ice is calculated.The lakes considered embrace a range of properties (depth, mixing,flushing rate, latitude and trophic status). The overall yearlyPP distribution is skewed to the left, suggesting the dominanceof low PP rates in the data set. When comparing lake types,no differences in average PP have been found among them. Inparticular, there are no clear areal PP differences among lakesof different trophic status on yearly, averaged basis, suggestingthat environmental limitations to PP also exist in lakes ofhigher trophic status. Volumetric-based PP can be better usedto outline PP-based trophic differences, but some degree ofoverlap is also apparent. Across all lake types (except in tropicallakes), the PP seasonal course experiences only one peak inthe year, but its timing is clearly different for each laketype. The seasonal variability of PP is lower in tropical lakes,as previously reported, but the variability of the other laketypes is roughly the same. Therefore, the effects of depth,mixing regime, flushing rate and nutrient status on PP seasonalityare difficult to ascertain since they appear to be counterbalancedby other more pervasive, local effects. Particularly, thereis no increase in temporal variability with the trophic statusof lakes, suggesting that PP seasonal control by physical variablesoverrides that of nutrients. Also, no significant relationshipbetween average PP and latitude has been found. Seasonal variabilityincreases as the yearly PP increases. On a relative basis, thereis a spatial gradient of seasonal variability of PP, which isweaker when seasonal variability of PP is considered in interyearcomparisons. Long-term (i.e. interannual) variability of PPis clearly related to increasing yearly averaged PP. Specifically,in temperate, stratifying lakes the seasonal time course ofPP is clearly different from that of phytoplankton biomass,suggesting an uncoupling of both variables as a result of differingP_max and losses throughout the year. On an average basis, environmentalvariables are poor predictors of areal daily PP, thereby implyingthat the interplay of factors is complex and changing throughoutthe year. PP under ice averages 10% of yearly PP, but its variabilityis high enough to make its measurement advisable.     

The corallivorous invertebrate Drupella aids in transmission of brown band disease on the Great Barrier Reef

Brown band disease (BrB) is an increasingly prevalent coral disease in the Indo-Pacific, but although the macroscopic signs of BrB have been associated with the ciliate Philaster guamensis, many aspects of its ecology remain unknown, particularly how the disease is transmitted among coral colonies. The aim of this study was to assess biotic factors affecting BrB transmission, explicitly testing whether corallivorous species contribute to disease spread. Several fish species were observed feeding on diseased tissue in the field, but did not influence either the progression or transmission rates of BrB on coral colonies in situ. In aquarium-based experiments, the butterflyfish Chaetodon aureofasciatus neither aided nor hindered the transmission of BrB from infected to uninfected corals. In contrast, the coral-feeding gastropod Drupella sp. was a highly effective vector of BrB, infecting more than 40 % of experimental colonies. This study also demonstrated the importance of injury in facilitating BrB infection, supporting the hypothesis that the BrB pathogen invades compromised coral tissue. In conclusion, disturbances and corallivorous activities that injure live corals are likely to contribute to increased occurrence of BrB provided that feeding scars create entry wounds sufficiently extensive to facilitate infection. These findings increase the understanding of the ecology of BrB, enabling better predictions of the prevalence and severity of this disease, and informing strategies for managing the impact of BrB on coral reefs.     

Molecular phylogeny of Babesia poelea from brown boobies (Sula leucogaster) from Johnston Atoll, central Pacific

The phylogenetic relationship of avian Babesia with other piroplasms remains unclear, mainly because of a lack of objective criteria such as molecular phylogenetics. In this study, our objective was to sequence the entire 18S, ITS-1, 5.8S, and ITS-2 regions of the rRNA gene and partial beta-tubulin gene of B. poelea, first described from brown boobies (Sula leucogaster) from the central Pacific, and compare them to those of other piroplasms. Phylogenetic analyses of the entire 18S rRNA gene sequence revealed that B. poelea belonged to the clade of piroplasms previously detected in humans, domestic dogs, and wild ungulates in the western United States. The entire ITS-1, 5.8S, ITS-2, and partial beta-tubulin gene sequence shared conserved regions with previously described Babesia and Theileria species. The intron of the beta-tubulin gene was 45 bp. This is the first molecular characterization of an avian piroplasm.     

Computer analysis of band variability in DNA fingerprints

Through the example of the distribution of PCR products DNA matrices of mouse tail tissue, a method of comparative analysis of DNA fingerprints is described. The PCR products were obtained using a 20-mer random primer flanking the Atp1b2 locus on mouse chromosome 11. A software program was designed that permits the simplification of comparison of DNA fragments variability or polymorphism detected on electrophoregrams from different individuals.     

Abundance and distribution of black band disease on coral reefs in the northern Florida keys

The abundance and distribution of black band disease on the reef building coralsMontastraea annularis, M. cavernosa, Colpophyllia natans, Diploria clivosa, D. labyrinthiformis andD. strigosa were determined at Algae Reef, Grecian Rocks and Key Largo Dry Rocks in the Key Largo National Marine Sanctuary, Florida, USA. During July and November of 1992 and July 1993, surveys of permanently marked sites covering 9424m² of reef tract showed that up to 0.72% of 1397 coral colonies of these species were infected with black band disease. The distribution of the disease among the thirty 20-meter diameter sites was clumped, suggesting that the disease is infectious. Year-round monitoring revealed that seasonal disease patterns varied between reefs. Three seasonal patterns were apparent: some coral colonies were infected year round; several colonies exhibited previously unreported reinfection on a seasonal basis; and some exhibited the widely reported pattern of infection limited to the warmer months of the year (sea water temperatures 25 °C or higher).     

Spatial heterogeneity in skeletal muscle microvascular blood flow distribution is increased in the metabolic syndrome

Previous studies have demonstrated that the metabolic syndrome is associated with impaired skeletal muscle arteriolar function, although integrating observations into a conceptual framework for impaired perfusion in peripheral vascular disease (PVD) has been limited. This study builds on previous work to evaluate in situ arteriolar hemodynamics in cremaster muscle of obese Zucker rats (OZR) to integrate existing knowledge into a greater understanding of impaired skeletal muscle perfusion. In OZR cremaster muscle, perfusion distribution at microvascular bifurcations (γ) was consistently more heterogeneous than in controls. However, while consistent, the underlying mechanistic contributors were spatially divergent as altered adrenergic constriction was the major contributor to altered γ at proximal microvascular bifurcations, with a steady decay with distance, while endothelial dysfunction was a stronger contributor in distal bifurcations with no discernible role proximally. Using measured values of γ, we found that simulations predict that successive alterations to γ in OZR caused more heterogeneous perfusion distribution in distal arterioles than in controls, an effect that could only be rectified by combined adrenoreceptor blockade and improvements to endothelial dysfunction. Intravascular (125)I-labeled albumin tracer washout from in situ gastrocnemius muscle of OZR provided independent support for these observations, indicating increased perfusion heterogeneity that was corrected only by combined adrenoreceptor blockade and improved endothelial function. These results suggest that a defining element of PVD in the metabolic syndrome may be an altered γ at microvascular bifurcations, that its contributors are heterogeneous and spatially distinct, and that interventions to rectify this negative outcome must take a new conceptual framework into account.