RELATIONSHIP BETWEEN TASTE AND CHEWING PATTERNS OF VISCO-ELASTIC MODEL FOODS

The jaw movements and muscular activity of masticatory muscles of five assessors, having bitterness thresholds about 8 μM quinine in water, were monitored throughout chewing of similar strength gelatin gels containing 0, 40, 70 or 100 μM quinine. Gel bitterness ratings were not related to sensory texture which was 78kN/m² by shear test. On average, 100 μM quinine gels were as bitter as 7 to 30 μM quinine in water, depending on the assessor. Chewing patterns were not affected by concentration of quinine in the gels. During mastication of acceptable gels, there appears to be no feedback from taste to the motor control of mastication. In gels of the same consistency and the same concentration of quinine, assessors who chewed more rated higher for bitterness. The implications for mimicking mastication by machine and the training of assessors for solid foods are discussed.     

Grazer control and nutrient limitation of phytoplankton biomass in two Australian reservoirs

1. Grazer and nutrient controls of phytoplankton biomass were tested on two reservoirs of different productivity to assess the potential for zooplankton grazing to affect chlorophyll/phosphorus regression models under Australian conditions. Experiments with zooplankton and nutrients manipulated in enclosures, laboratory feeding trials, and the analysis of in-lake plankton time series were performed. 2. Enclosures with water from the more productive Lake Hume (chlorophyll a = 3–17.5 μg l^–1), revealed significant zooplankton effects on chlorophyll a in 3/6, phosphorus limitation in 4/6 and nitrogen limitation in 1/6 of experiments conducted throughout the year. Enclosures with water from the less productive Lake Dartmouth (chlorophyll a = 0.8–3.5 μg l^–1), revealed significant zooplankton effects in 5/6, phosphorus limitation in 5/6 and nitrogen limitation in 2/6 of experiments. 3. While Lake Hume enclosure manipulations of the biomass of cladocerans (Daphnia and Diaphanosoma) and large copepods (Boeckella) had negative effects, small copepods (Mesocyclops and Calamoecia) could have positive effects on chlorophyll a. 4. In Lake Hume, total phytoplankton biovolume was negatively correlated with cladoceran biomass, positively with copepod biomass and was uncorrelated with total crustacean biomass. In Lake Dartmouth, total phytoplankton biovolume was negatively correlated with cladoceran biomass, copepod biomass and total crustacean biomass. 5. In both reservoirs, temporal variation in the biomass of Daphnia carinata alone could explain more than 50% of the observed variance in total phytoplankton biovolume. 6. During a period of low phytoplankton biovolume in Lake Hume in spring–summer 1993–94, a conservative estimate of cladoceran community grazing reached a maximum of 0.80 day^–1, suggesting that Cladocera made an important contribution to the development of the observed clear-water phase. 7. Enclosure experiments predicted significant grazing when the Cladocera/Phytoplankton biomass ratio was greater than 0.1; this threshold was consistently exceeded during clear water phase in Lake Hume. 8. Crustacean length had a significant effect on individual grazing rates in bottle experiments, with large Daphnia having highest rates. In both reservoirs, mean crustacean length was negatively correlated with phytoplankton biovolume. The observed upper limit of its variation was nearly twice as high compared to other world lakes.     

Okeanomyces, a new genus to accommodate Halosphaeria cucullata (Halosphaeriales, Ascomycota)

The taxonomic affinity of Halosphaeria cucullata to Halosphaeria is reassessed based on a recent collection of this fungus. Halosphaeria cucullata is characterized by immersed, darkly coloured ascomata, clavate asci which deliquesce very early in development, and cylindrical ascospores with or without a polar cap-like appendage at one end. In a phylogenetic analysis of the LSU rDNA sequences from members of the Halosphaeriaceae, H. cucullata did not form a monophyletic clade with H. appendiculata , the type species of the genus. These results suggest that H. cucullata should not be included in Halosphaeria . Okeanomyces gen. nov. is proposed to accommodate this fungus.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 223–229.     

HABITAT AND DIET OF EARLY STAGES OF SEPIA OFFICINALIS L. (CEPHALOPODA) IN MORBIHAN BAY, FRANCE

The nursery grounds of Sepia officinalis were identified inthe Gulf of Morbihan, on the Atlantic coast of France, and theirabiotic and biotic features described. From the measurementof the young cuttlefish captured, their growth and developmentcould be followed through a period of five months. Analysisof the stomach contents of the cuttlefish and identificationof the prey consumed gave a measure of their feeding activityand diet. The young animals were concentrated in the two parts(East and West) of Morbihan Bay. These were distinguished bydifferent sediments (sandy-mud in the East and sand with shell-debrisin the West) and by water temperature (higher in the East whichallow a greater growth of the young cuttlefish). These sitesare rich in crustaceans Amphipoda, Brachyura and Macrura whichcompose the diet of young cuttlefish. Fish (Gobiidae and Syngnathidae)appear in the diet from August. The feeding activity of thecuttlefish (given by the repletion quotient) increased fromJune to August reaching about 80% in both parts of the Bay.It decreased to nearly 50% in September and October. (Received 11 February 1997; accepted 25 August 1997)     

Disentangling stand and environmental correlates of aboveground biomass in Amazonian forests

Tropical forests contain an important proportion of the carbon stored in terrestrial vegetation, but estimated aboveground biomass (AGB) in tropical forests varies two‐fold, with little consensus on the relative importance of climate, soil and forest structure in explaining spatial patterns. Here, we present analyses from a plot network designed to examine differences among contrasting forest habitats (terra firme, seasonally flooded, and white‐sand forests) that span the gradient of climate and soil conditions of the Amazon basin. We installed 0.5‐ha plots in 74 sites representing the three lowland forest habitats in both Loreto, Peru and French Guiana, and we integrated data describing climate, soil physical and chemical characteristics and stand variables, including local measures of wood specific gravity (WSG). We use a hierarchical model to separate the contributions of stand variables from climate and soil variables in explaining spatial variation in AGB. AGB differed among both habitats and regions, varying from 78 Mg ha^?1 in white‐sand forest in Peru to 605 Mg ha^?1 in terra firme clay forest of French Guiana. Stand variables including tree size and basal area, and to a lesser extent WSG, were strong predictors of spatial variation in AGB. In contrast, soil and climate variables explained little overall variation in AGB, though they did co‐vary to a limited extent with stand parameters that explained AGB. Our results suggest that positive feedbacks in forest structure and turnover control AGB in Amazonian forests, with richer soils (Peruvian terra firme and all seasonally flooded habitats) supporting smaller trees with lower wood density and moderate soils (French Guianan terra firme) supporting many larger trees with high wood density. The weak direct relationships we observed between soil and climate variables and AGB suggest that the most appropriate approaches to landscape scale modeling of AGB in the Amazon would be based on remote sensing methods to map stand structure.     

Cytogenetic and molecular characterization of morphologically variable Sisyrinchium micranthum (Iridaceae) in southern Brazil

Sisyrinchium micranthum is native to southern Brazil and shows a wide range of morphological variation in this region. This study was performed to compare individuals of this species in terms of traits such as morphology, chromosome number, meiotic behaviour, pollen viability and genetic diversity using inter simple sequence repeat markers. First, general morphological aspects were evaluated and plants were classified into three morphological categories (CI, CII and CIII) to analyse the cytogenetic and genetic data. Three chromosome numbers corresponding to three ploidies were found: 2n = 2x = 16, 2n = 4x = 32 and 2n = 6x = 48. All morphological types showed regular meiotic behaviour and high meiotic index values and pollen viability. CII is the most frequent in southern Brazil. The most common haploid chromosome number, n = 8, has not been reported previously in this species. The percentage of polymorphic loci ranged from 6.45 to 61.29% for each accession. Molecular and cytogenetic analyses indicate that some S. micranthum accessions may have more than one ploidy. This study represents the first effort to characterize this taxonomically complex species based on cytogenetic and genetic aspects. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 350–364.