Evidence for successional development in Antarctic hypolithic bacterial communities

Hypoliths (cryptic microbial assemblages that develop on the undersides of translucent rocks) are significant contributors to regional C and N budgets in both hot and cold deserts. Previous studies in the Dry Valleys of Eastern Antarctica have reported three morphologically distinct hypolithic community types: cyanobacteria dominated (type I), fungus dominated (type II) and moss dominated (type III). Here we present terminal-restriction fragment length polymorphism analyses to elucidate the bacterial community structure in hypolithons and the surrounding soils. We show clear and robust distinction in bacterial composition between bulk surface soils and hypolithons. Moreover, the bacterial assemblages were similar in types II and III hypolithons and clearly distinct from those found in type I. Through 16S rRNA gene 454 pyrosequencing, we show that Proteobacteria dominated all three types of hypolithic communities. As expected, Cyanobacteria were more abundant in type I hypolithons, whereas Actinobacteria were relatively more abundant in types II and III hypolithons, and were the dominant group in soils. Using a probabilistic dissimilarity metric and random sampling, we demonstrate that deterministic processes are more important in shaping the structure of the bacterial community found in types II and III hypolithons. Most notably, the data presented in this study suggest that hypolithic bacterial communities establish via a successional model, with the type I hypolithons acting as the basal development state.     

An ultrastructural investigation of the early stages of oocyte differentiation in Actinia fragacea (Cnidaria; Anthozoa)

Individuals from a population of the intertidal sea anemone Actinia fragacea (Tugwell) were collected at approximately monthly intervals over an 18 month period. Samples of gonad were removed from each anemone and examined by light and electron microscopy. During late spring and early summer, large numbers of small cells were seen in the endoderm of the female gonads, lying close to the mesoglea. For convenience, these cells were classified into three types. Type I cells are 6–9 μm in diameter, with relatively very large nuclei, which may contain synaptinemal complexes, and scant cytoplasm containing few organelles. Type II cells are larger, reaching 15 μ m in diameter, with more abundant cytoplasm containing more organelles and inclusions. The nucleus is more dense, but may also contain synaptinemal complexes. Type III cells are less common. They are similar in size to Type II cells, but their nuclei contain irregular dense chromatin masses, and the nuclear envelope is incomplete or absent. The possible significance of the various cell types is discussed. It is suggested that Type I cells are oocytes at a very early stage of differentiation and that Type II cells are rather later oocytes. The status of the Type III cells is uncertain.     

The external morphology and distribution of cuticular hair organs on the claws of the American lobster, Homarus Americanus (Milne-Edwards)

Four classes of microscopic cuticular hair organs were found on the chelae of Homarus americanus (Milne-Edwards). Type I and Type II organs possess long single sensillae, 30–60 μm and 70–130 μm, respectively. Type III organs are toroid bumps 20–30 μm in diameter, with a small tuft of fibers projecting from the center. Type IV organs are small conical hairs ≈ 1 μm in length.Type IV organs were uniformly distributed over the claws. The distributions of Types I, II, and III organs were analysed through multivariate analysis of variance (MANOVA) with respect to claw, side, and area. Type I organs showed significance of the three-way interaction only. Type II organs showed significance of side, area, and the claw by area interaction. Type III organs showed significance of area, and all interactions. Changes in number and density of Types I, II and III organs, and in number of Type IV organs, were found with growth.     

Predispersal seed-predation by insects in the Venezuelan Central Plain: Overall patterns and traits that influence its biology and taxonomic groups

Predispersal seed predation (PSP) by insects was studied in a plant community of the Venezuelan Central Plain (VCP). The main goal was to examine to what extent vegetation structure and fruit–seed attributes determined the incidence of PSP by insects at the community level. We studied a total of 187 species from 59 families, in five habitat types. The proportion of seed-predated plant species (N=89; 47.6% of the total) was explained by different factors such as the abundance of legume families, plant species richness, fruit dehiscence, seed biomass, and starch content. Coleoptera was the most diverse taxonomic order of insect seed predators, with Bruchidae and Curculionidae showing the largest number of genera and species, followed by Lepidoptera (Pyralidae). Bruchidae and Pyralidae, but not Curculionidae, tended to be separated according to vegetation attributes, such as vegetation structure and flowering and fruiting phenology. In addition, Bruchidae was associated with dehiscent fruits, legumes, epizoochory, and granivory, whereas Curculionidae was more related with indehiscent fruits and endozoochory, and Pyralidae with abiotic seed dispersal. Bruchid larvae tended to prey upon single seeds, whereas larvae of Lycaenidae usually preyed upon more than one seed per fruit; Curculionidae did not show any clear pattern on this. One larva developing in a single seed (Type I) was the most common type of PSP, closely followed by one or more larvae developing outside seeds within the fruit (Type II). Type III (seed predation by adult insects inside the fruit) was the least common. Type I appears to occur most frequently in climbers, in the forest–savanna transition habitat, and in those cases in which insect adults emerged during the rainy season. By contrast, Types II and III tended to be associated with annual herbs, the lowest stratum (0.05–0.6 m), and disturbed areas. Moreover, Type I was usually found in samaras, drupes, and indehiscent fruits, whereas Type II and Type III were more commonly observed in capsules. Type I and Type II seeds differed in their nutritional composition, which in turn appears to affect seed predation specialization. The number of insect seed predator species and plant richness per habitat were positively correlated. The number of seed predator species was associated with the abundance of trees and climbers because more complex plant life forms offer a large variety of resources, woody species frequently had fruits and seeds larger than herbaceous species, and trees and climbers showed the lowest values of host specificity. To our knowledge, this study is the first one that characterizes the community of predispersal seed predators and simultaneously evaluates ecological, morphological, and nutritional factors determining the groups of seed predators and how PSP occurred.     

Coiling dimorphism within a genetic type of the planktonic foraminifer Globorotalia truncatulinoides

The coiling direction—sinistral (left-coiled) or dextral (right-coiled)—of planktonic foraminiferal shells is a classical proxy used to assess past environmental changes and to understand their evolutionary patterns. Globorotalia truncatulinoides is composed of five different genetic types (I to V), each with a specific biogeographic distribution. So far, type II is the only type within which both coiling types have been frequently found. Here we examine the coiling direction as a dimorphic variation in a single genetic type, and show that the two forms with different coiling directions differ in ecology. The studied 140 left- and 137 right-coiled specimens from eight depth layers at four stations in the Sargasso Sea all belonged to Type II, based on the phylogenetic analyses of the ITS (internal transcribed spacer) region of ribosomal DNA. The distributions of left- and right-coiled Type II (Type II-L and II-R) differed strongly: Type II-L dominated between 400 and 200 m depth in the central water mass, whereas Type II-R was common in the top 200 m of the subtropical gyre. The left- and right-coiled forms are thus associated with different water masses. However, the vertical distribution along a temperature gradient indicates that their coiling direction is not determined by temperature, and might have some genetic basis. Our molecular phylogenetic analyses showed that the two forms probably share the same gene pool through their dispersals between different water masses. Moreover, the lineage of G. truncatulinoides is young (< 3 Ma), which might not be long enough to evolve into two lineages with opposite coiling direction. We discuss the practical and theoretical usefulness of a simple genetic model for coil dimorphism, in order to build testable hypotheses regarding the evolutionary history of planktonic foraminifera at the population level.     

Control of isoperoxidases involved in chlorophyll degradation of stored broccoli (Brassica oleracea) florets by heat treatment

Changes in isoperoxidases involved in chlorophyll (Chl) degradation of stored broccoli (Brassica oleracea L.) florets and their control by heat treatment (HT) were determined. Chl a and b contents in non-heat-treated broccoli florets decreased greatly after 2 days at 15 degrees C, whereas the contents in heat-treated florets (50 degrees C for 2 h) showed almost no change. Three isoperoxidases involved in Chl degradation were detected by means of molecular exclusion chromatography and the molecular weights of those isoperoxidases were about 95 (Type I), 67 (Type II) and 56 (Type III) kDa, respectively. Only Type I was detected in broccoli florets immediately after harvest, and its activity in non-heat-treated broccoli increased greatly during storage. Both Type II and Type III were present in non-heat-treated broccoli with floret senescence. HT suppressed the enhancement of all of the isoperoxidase activities. Cycloheximide treatment also effectively retarded the increase in Types I, II and III isoperoxidase activities concomitant with the suppression of floret yellowing. The K(m) values corresponding to Chl a of Type II and Type III were lower than Type I, and the V(max)/K(m) values corresponding to Chl a of Type II and Type III were higher than Type I. This suggests that both Types II and III could be closely associated with Chl degradation in broccoli florets and that HT might inhibit floret senescence by suppression of isoperoxidase activities.     

Vegetation–environment relationships and classification of the seasonal savannas in Venezuela

The seasonal savannas dominated by the C₄ grasses of the genus Trachypogon, are widespread in northern South America. In Venezuela, they extend from the central lowland Llanos to intermediate elevations in the Coastal and Andean Mountains and to the Guiana Plateau (Gran Sabana) in the south. This study aims to classify these savannas and to understand the environmental factors that determine their composition and structure. Thirty-seven sites were sampled, plant cover and density were measured in 376 one square meter quadrats and the importance value index (IVI) was calculated. Climate data were obtained from climatological stations and soil properties were analyzed. The results were classified by clustering and TWINSPAN. Floristic and environmental data were ordered with the canonical correspondence analysis (CCA).Trachypogon savannas are heterogeneous, both floristically and environmentally. An altitudinal gradient of 2000 m separates the intermediate elevation Coastal Mountains (Type I) and the Guiana savannas (Type II) from the lowland Llanos. In the lowlands, sparsely covered and treeless communities on extremely oligotrophic and sandy soils (Type IV) differ structurally and floristically from woody savannas (Type III). The floristics and structure of the savannas respond directly or indirectly to elevation and water and nutrient availability. These responses were evidenced by: (a) floristic composition, as Neotropical lowland savanna species merged with those of the Andean sub-páramo in Type I savannas or with those from the Guianan flora in Type II savannas. (b) Species richness, which ranged from an average of 13.8 per site in sandy Type IV savannas to 38.9 per site in Type I intermediate elevation savannas. (c) Community physiognomy, which changes from an homogeneous herbaceous matrix with dispersed trees in Type III savannas to a shrubby Type I savannas to “treeless” Types II and IV savannas. (d) Plant cover which varied from 93.8% in the fertile Type I savannas to around 80% in the sandy oligotrophic savannas of Types II and IV. Each savanna type is related to one of the major geomorphological regions of Venezuela.     

Community structure of ground beetles (Coleoptera: Carabidae) along an altitudinal gradient on Mt. Sobaeksan,Korea

We conducted this study to determine the diversity patterns, community structures, and seasonality of ground beetle assemblages along an altitudinal gradient (437–1420 m) on Mt. Sobaeksan, Korea. Ground beetles were collected by pitfall traps installed along an altitudinal gradient (437, 757, 1100, and 1420 m). A total of 32 species belonging to seven subfamilies were identified from 3259 collected ground beetles. The diversity pattern of the ground beetle assemblage according to altitude was neither monotonic decreased nor hump-shaped. However, subfamily assemblages and wing form diversity patterns differed according to altitude and may be correlated with altitude or some other environmental variables. The dominant species were Synuchus cycloderus (29.4%) and Eucarabus sternbergi sobaeksanensis (15.4%) and their seasonal activities according to altitude were similar. According to non-metric multidimensional scaling, ground beetles and altitudes could be divided into two distinct groups: a low altitude group (437–757 m) and a high altitude group (1100–1420 m). Some species were particularly abundant at high altitudes, such as Aulonocarabus koreanus kwonileeique and Poecilus nitidicollis, while others were highly abundant at low altitudes, such as Pterostichus audax, Pterostichus ishikawai, and Synuchus species.     

Identifying plant species and communities across environmental gradients in the Western Himalayas: Method development and conservation use

Phytosociological attributes of plant species and associated environmental factors were measured in order to identify the environmental gradients of major plant communities in the Naran Valley, Himalayas. The valley occupies a distinctive geographical setting on the edge of the Western Himalaya near the Hindukush range and supports a high biodiversity; pastoralism is the main land use. There have been no previous quantitative ecological studies in this region. This study was undertaken to (i) analyze and describe vegetation using classification and ordination techniques, (ii) identify environmental gradients responsible for plant community distributions and (iii) assess the anthropogenic pressures on the vegetation and identify priorities for conservation. Phytosociological characteristics of species were measured alongside environmental variables. A total of 198 species from 68 families were quantified at 144 stations along 24 transects across an elevation range of 2450–4100 m. Correspondence Analysis techniques i.e., Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) were used to determine vegetation–environment relationships. Results show vegetation changes with altitude from moist-cool temperate communities characterized by woody species, to more dry-cold subalpine and alpine herbaceous communities. Plant species diversity is optimal at middle altitudes (2800–3400 m); at lower altitudes (2400–2800 m) it is reduced by anthropogenic impacts and at higher altitudes (3400–4100 m) by shallow soils and high summer grazing pressure. A large number of plant species of conservation concern were identified in the study and an assessment made of the main threats to their survival.     

Morphology, ontogeny and histochemistry of secretory trichomes of Geranium robertianum (Geraniaceae)

Geranium robertianum bears three types of glandular uniseriate trichomes which originate from a single protodermal cell and develop through periclinal divisions. Type I trichomes are procumbent and have an oval apical cell, two stalk cells and a basal cell. Type II trichomes are erect and have a pear shaped apical cell, two stalk cells and a basal cell. Type III trichomes are much longer than the other two types and have an elongated apical cell, five long stalk cells and a basal cell. Type I and type II trichomes are common on leaves while III trichomes are more abundant on flower structures.
Type I and type II trichomes secrete terpenoids and phenols. Type III trichomes are characterized by the accumulation of anthocyanins in the apical cell and secrete flavonoids.     

The Permian Moradi Formation of northern Niger: Paleosol morphology,petrography and mineralogy

Three basic paleosol morphologies, named Type A, Type B and Type C, are described from the middle–upper Permian strata of the Moradi Formation, Tim Mersoi Basin, northern Niger. The Moradi Formation is a typical alluvial redbed succession dominated by red mudrocks with fine to coarse-grained pebbly channel sandstones and matrix-breccias. Type A paleosols are hosted by well-sorted fine to medium grained trough cross bedded and massive sandstones and preserve abundant vertical to horizontal micritic and microspar calcite tubules, interpreted as rhizoliths. Lateral variability of rhizoliths in Type A paleosols, and their close association with fluvial channel-fill sediments suggests they are the roots of grove stands of phreatophytic vegetation that grew within unstable anabranching stream systems. Type B paleosols are hosted by mudrocks and preserve well-developed ped structure, abundant micritic calcite nodules and vertically-stacked micritic calcite nodular bodies, as well as rare calcite with satin-spar texture interpreted as a pseudomorphic replacement of pedogenic gypsum. The morphology of Type B paleosols suggests they were formed in well-drained floodplain deposits on stable landforms. Type C paleosols are similar to Type B but preserve pedogenic structures indicative of soil volume expansion and contraction, as well as more abundant Stage II pedogenic carbonate nodules. The morphology of Type C paleosols suggests that they developed periodically rather than seasonally in poorly-drained deposits that nevertheless occupied a relatively stable part of the landscape such as the plains flanking ephemeral lakes or sabkhas.X-ray diffraction analysis of the < 2 μm fraction from the Moradi Formation strata indicates that paleosol phyllosilicates are composed of illite, smectite, and occasionally kaolinite and talc. Illite is likely a detrital mineral, whereas smectite and kaolinite are likely pedogenic weathering products. The presence of talc in the Moradi Formation paleosols is unusual. It is limited to paleosol horizons that also preserve evidence for pedogenic gypsum accumulation and is therefore most likely related to a pedogenic weathering process. It is possible that this talc is a relatively low-temperature (~ 50–100 °C) diagenetic alteration product of pedogenic Mg–phyllosilicates such as sepiolite.The range of morphologies, petrographic textures and mineralogy of the paleosol profiles indicates semi-arid to hyper-arid climatic setting. This paleoclimatic reconstruction is in agreement with Middle and Late Permian conceptual paleoclimate models and quantitative general circulation models. Nevertheless, and in spite of an arid climate, Moradi paleosols and their host strata also indicate a relatively shallow groundwater table. Importantly, this shallow groundwater resource undoubtedly helped to support the moderately diverse fossil vertebrate assemblage and large-stature macrophytes preserved in the Moradi Formation.     

Cells producing insulin-like androgenic gland hormone of the giant freshwater prawn, Macrobrachium rosenbergii, proliferate following bilateral eyestalk-ablation

We found that the androgenic gland (AG) of Macrobrachium rosenbergii possesses three cell types. Type I cells are small polygonal shaped-cells (13.4 μm in diameter), stain strongly with hematoxylin-eosin (H&;E), have abundant multilayered rough endoplasmic reticulum (rER), and nuclei containing mostly heterochromatin. Type II cells are slightly larger (18.6 μm in diameter), stain lightly with H&;E, have rER with dilated cisternae, and nuclei containing mostly euchromatin. Type III cells (previously undescribed) are similar in size and shape to type I cells, but the cytoplasm is unstained and they have a high amount of smooth endoplasmic reticulum (sER) and mitochondria with tubular cristae. Bilateral eyestalk-ablation resulted in AG hypertrophy with a proliferation and predominance of type I cells as determined by bromodeoxyuridine (BrdU) assays. Expression of insulin-like androgenic gland hormone (Mr-IAG), determined by immunohistochemistry, was weak in type I cells, strong in type II cells of both the intact and eyestalk-ablated, and negative in type III cells. It was also detected in spermatogonia, nurse cells, and epithelium lining of the spermatic duct. The function of Mr-IAG in these tissues is yet to be elucidated but the distribution implies a strong role in male reproduction.     

Selection of Type I and Type II methanotrophic proteobacteria in a fluidized bed reactor under non-sterile conditions

Type II methanotrophs produce polyhydroxybutyrate (PHB), while Type I methanotrophs do not. A laboratory-scale fluidized bed reactor was initially inoculated with a Type II Methylocystis-like dominated culture. At elevated levels of dissolved oxygen (DO, 9 mg/L), pH of 6.2–6.5 with nitrate as the N-source, a Methylobacter-like Type I methanotroph became dominant within the biofilms which did not produce PHB. A shift to biofilms capable of PHB production was achieved by re-inoculating with Type II Methylosinus culture, providing dissolved N₂ as the N-source, and maintaining a low influent DO (2.0 mg/L). The resulting biofilms contained both Types I and II methanotrophs. Batch tests indicated that biofilm samples grown with N₂ became dominated by Type II methanotrophs and produced PHB. Enrichments with nitrate or ammonium were dominated by Type I methanotrophs without PHB production capability. The key selection factors favoring Type II were N₂ as N-source and low DO.     

Correlation of the KHS Tuff of the Kibish Formation to volcanic ash layers at other sites, and the age of early Homo sapiens (Omo I and Omo II)

Hominin specimens Omo I and Omo II from Member I of the Kibish Formation, Ethiopia are attributed to early Homo sapiens, and an age near 196 ka has been suggested for them. The KHS Tuff, within Member II of the Kibish Formation has not been directly dated at the site, but it is believed to have been deposited at or near the time of formation of sapropel S6 in the Mediterranean Sea. Electron microprobe analyses suggest that the KHS Tuff correlates with the WAVT (Waidedo Vitric Tuff) at Herto, Gona, and Konso (sample TA-55), and with Unit D at Kulkuletti in the Ethiopian Rift Valley. Konso sample TA-55 is older than 154 ka, and Unit D at Kulkuletti is dated at 183 ka. These correlations and ages provide strong support for the age originally suggested for the hominin remains Omo I and Omo II, and for correlation of times of deposition in the Kibish region with formation of sapropels in the Mediterranean Sea. The Aliyo Tuff in Member III of the Kibish Formation is dated at 104 ka, and correlates with Gademotta Unit 15 in the Ethiopian Rift Valley.     

Embryo production and progesterone profiles in ewes superovulated with different hormonal treatments

The superovulatory response and embryo yield following hormonal treatments of Merino ewes during late spring and their estrous cycle were evaluated. Ewes (n=17) were treated with progestagen-impregnated sponges and assigned to Group I (800 IU PMSG plus 11.5 mg FSH-p); Group II (1200 IU PMSG); Group III (1600 IU PMSG). Ewes were naturally mated and followed by laparotomy 6 days later. After laparotomy, ewes were injected with a prostaglandin analogue (PGF) and serum samples were obtained prior to surgery and then for 25 days to measure progesterone (P4) by radioimmunoassay. There were no differences among groups neither for estrous incidence (Group I: 83.3%; Group II: 83.3%; Group III: 100%), nor for the time interval to estrous onset (Group I: 26.4±2.4 h; Group II: 28.8±2.9 h; Group III: 24.0±3.8 h). Group I had more corpora lutea than Group II (14.2±1.2 and 6.2±0.8; P<0.05), and Group III was intermediate (11.0±3.0). There was a low incidence of persistent follicles in all treatments (Group I: 0.5±0.5; Group II: 0.6±0.4; Group III: 1.8±1.2). Number of collected ova were 9.0±2.6, 3.8±0.6 and 6.5±0.9 for Groups I, II and III, respectively. Significant differences in number of ova were detected between Groups I and II. Unfertilized ova did not differ among groups (Group I: 3.5±1.0; Group II: 2.8±0.8; Group III: 5.2±1.4; P>0.05). Embryos and high viability embryos were higher (P<0.05) in Group I (5.2±1.9 and 4.8±2.0) than in Group II (1.0±0.5 and 1.0±0.5) or Group III (1.2±0.6 and 1.0±0.5). Total plasma progesterone (P4) and P4 per corpus luteum before PGF administration did not vary (P>0.05) among groups (Group I: 71.0±14.7 and 4.9±0.7 nmol/l; Group II: 50.6±13.3 and 7.9±1.6 nmol/l; Group III: 90.4±42.6 and 6.8±1.8 nmol/l). There was a significant and positive correlation between P4 before PGF administration and number of corpora lutea (r=0.76). No significant differences were detected among groups for: interval PGF to P4 <3.18 nmol/l (Group I: 2.7±0.3 days; Group II: 1.8±0.6 days; Group III: 2.2±0.5 days), cycle length (Group I: 18.3±1.4 days; Group II: 17.9±0.5 days; Group III: 16.8±0.9 days), duration of P4 levels <3.18 nmol/l (Group I: 11.3±1.9 days; Group II: 7.1±1.0 days; Group III: 7.2±2.4 days), duration of P4 levels ≥3.18 nmol/l (Group I: 7.0±1.3 days; Group II: 10.8±0.8 days; Group III: 9.5±1.7 days) and peak of P4 (Group I: 7.4±0.4 nmol/l; Group II: 10.8±1.6 nmol/l; Group III: 9.2±1.9 nmol/l). It was concluded that PMSG–FSH-p treatment was more efficient than PMSG alone for superovulation and embryo production in ewes while P4 profiles were similar among groups.     

Effect of partial replacement of concentrates with jackfruit (Artocarpus heterophyllus) leaves on growth performance of kids grazing on native pasture of Tripura,India

Fifteen Black Bengal kids of about 3 months of age and body weight ranging from 3.8 to 4.9 kg were randomly distributed into three groups of five. Kids grazed native pasture 8 h/d. The kids in group I received supplementary concentrate (maize 35%, mustard cake 32%, rice bran 30%, mineral mixture 2% and common salt 1%) at approximately 2% of BW. However, 25 and 50% of the concentrate was replaced with jackfruit leaves for groups II and III, respectively. Total dry matter intake (DMI) was significantly higher in groups II and III than for group I due to greater forage consumption. Digestibility of CP (P < 0.05) decreased and that of NDF increased (P < 0.01) with increasing level of jackfruit leaves in the diet. Digestibility of ADF (P < 0.01), hemi cellulose (P < 0.05) and cellulose (P < 0.01) was higher in groups II and III in comparison to group I. Ruminal pH and TVFA concentration were not significantly different among the groups; however, rumen ammonia-N concentration decreased (P < 0.01) with increased level of jackfruit leaves in the diet. Similarly, plasma urea nitrogen and blood glucose levels were also reduced (P < 0.05) with increasing level of jackfruit leaves in the diet Average daily gain (ADG) was 47.33, 45.11 and 35.56 g/d in groups I, II and III, respectively. ADG and DMI/kg gain were not adversely affected when the level of replacement was restricted to 25%; however, at the 50% of replacement both parameters were adversely affected (P < 0.05). From the results of this experiment, it was concluded that jackfruit leaves might replace 25% of the supplemental concentrate for growing kids grazing in native pasture of northeast India.     

Applying remote sensing techniques to monitoring seasonal and interannual changes of aquatic vegetation in Taihu Lake,China

Knowledge of the composition and areal distribution of aquatic vegetation types, as well as their seasonal and interannual variations, is crucial for managing and maintaining the balance of lake ecosystems. In this study, a series of remotely sensed images with a resolution of 30 m (HJ-CCD and Landsat TM) were collected and used to map the distribution of aquatic vegetation types in Taihu Lake, China. Seasonal and interannual dynamics of aquatic vegetation types were explored and analyzed. The distribution areas of Type I (emergent, floating-leaved and floating vegetation) and Type II (submerged vegetation) were used to model their growing season phenology by double logistic functions. The resulting double logistic models showed, the area of Type I reached its peak in mid-August, and the maximum area for Type II occurred in mid-September. From 1984 to 2013, Type I area increased continuously from 59.75 km² to 148.00 km² (R² = 0.84), whereas the area covered by Type II first increased and then decreased, with a trend conforming to a significant quadratic curve (R² = 0.83). The eutrophication and stable state of Taihu Lake was assessed using a simple indicator which was expressed as a ratio of Type II area to Type I area. The results showed that the eutrophication in the lake might have been increasing in the area studied since 2000. Additionally, the results showed that air temperature had likely a direct effect on the growth of Type I (R² = 0.66) and a significant, but delayed, effect on the growth of Type II.     

Protection of Selenium on Hepatic Mitochondrial Respiratory Control Ratio and Respiratory Chain Complex Activities in Ducklings Intoxicated with Aflatoxin B<Subscript>1</Subscript>

To investigate the protection of selenium on hepatic mitochondrial functions, 90 7-day-old ducklings were randomly divided into three groups (groups I–III). Group I was used as a blank control. Group II was administered with aflatoxin B₁ (0.1 mg/kg body weight). Group III was administered with aflatoxin B₁ (0.1 mg/kg body weight) plus selenium (sodium selenite, 1 mg/kg body weight). All treatments were given once daily for 21 days. The results showed that the activities of hepatic mitochondrial complexes I–IV in group II ducklings significantly decreased when compared with group I (P < 0.01). Furthermore, the activities of hepatic mitochondrial complexes I–IV in group III significantly increased when compared with group II (P < 0.05). The hepatic mitochondrial respiratory control ratio (RCR) in group II ducklings significantly decreased when compared with group I (P < 0.01). In addition, the hepatic mitochondrial RCR in group III significantly increased when compared with group II (P < 0.05). These results revealed that the aflatoxin B₁ significantly induced hepatic mitochondrial dysfunction in the activities of hepatic mitochondrial respiratory chain complexes I–IV and the RCR in ducklings. However, sodium selenite could significantly ameliorate the negative effect induced by aflatoxin B₁.     

Morphological features of Class I,II and III malocclusions of Saudi adolescents

AimsThis cross-sectional study compared and contrasted the morphological characteristics of Class I, II and III malocclusions in an adolescent Saudi population.MethodsAdolescent Saudis with Angle’s Class I, II and III malocclusions were selected from orthodontic patients’ records. Angular and linear measurements were compared between the three groups. Cephalometric analysis was performed using the VistadentOC® software. Multifactorial ANOVA for angular and linear measurements between and within groups.ResultsOrthodontic records of 300 patients were included. There was no significant difference between and within groups in age and distribution of Angle’s classification, p > 0.05. Multifactorial ANOVA showed that there were significant interactions between gender and malocclusions in skeletal, dental and soft tissue measurements, p < 0.05. There were significant differences in the sagittal and vertical skeletal measurements between groups, p < 0.05. The dental measurements were also significantly different in most of the measurements (p < 0.05). Moreover, there were significantly different readings among the groups in the soft tissue analysis.ConclusionMorphological characteristics of adolescent Saudis show unique differences between gender and malocclusions, more so in Class III malocclusions. Class II and III malocclusions also show skeletal differences amongst the groups.     

Hypolithic microbial communities of quartz rocks from Miers Valley, McMurdo Dry Valleys, Antarctica

The McMurdo Dry Valleys region of eastern Antarctica is a cold desert that presents extreme challenges to life. Hypolithic microbial colonisation of the subsoil surfaces of translucent quartz rocks represent a significant source of terrestrial biomass and productivity in this region. Previous studies have described hypoliths as dominated by cyanobacteria. However, hypoliths that occur in the lower Dry Valleys such as the Miers, Garwood and Marshall Valleys are unusual as they are not necessarily cyanobacteria-dominated. These hypoliths support significant eukaryal colonisation by fungi and mosses in addition to cyanobacteria-dominated bacterial assemblages and so have considerable ecological value in this barren landscape. Here, we characterise these novel hypoliths by analysis of environmental rRNA gene sequences. The hypolithic community was demonstrated to be distinct from the surrounding soil and non-translucent rocks. Hypoliths supported cyanobacterial signatures from the Oscillatoriales and Nostocales. Other heterotrophic bacterial signatures were also recovered, and these were phylogenetically diverse and spanned 8 other bacterial phyla. Archaeal phylotypes recovered were phylogenetically affiliated with the large group of unclassified, uncultured Crenarcheota. Eukaryal phylotypes indicated that free-living ascomycetous fungi, chlorophytes and mosses (Bryum sp.) were all supported by these hypoliths, and these are thought to be responsible for the extensive eukaryotic biomass that develops around quartz rocks.