Effects of Habitat Connectivity on the Abundance and Species Richness of Coral Reef Fishes: Comparison of an Experimental Habitat Established at a Rocky Reef Flat and at a Sandy Sea Bottom

Coral reef fish assemblages are widely recognized for the coexistence of numerous species, which are likely governed by both coral diversity and substratum complexity. However, since coral reefs provide diverse habitats due to their physical structure and different spatial arrangements of coral, findings obtained from an isolated habitat cannot necessarily be applied to fish assemblages in other habitats (e.g. continuous habitats). The aim of this study, therefore, was to determine by a field experiment whether habitat connectivity (spatial arrangement of coral colonies) affects abundance and species richness of fishes in an Okinawan coral reef. The experiment consisted of transplanted branching coral colonies at a 4m×8m quadrat at both a rocky reef flat and sandy sea bottom. Generally, the abundance of fishes was greater at the sandy sea bottom, especially for three species of pomacentrids, one species of labrids, one species of chaetodontids and two species of apogonids. Species–area curves showed that the species richness of fishes was significantly greater in the quadrat at the sandy sea bottom at 3, 6 and 9 months after the start of the experiment. The rate of increase in abundance of fishes per area was significantly greater in the quadrat at the sandy sea bottom over the study period. The results of rarefaction analyses showed that the rate of increase in species richness per abundance was significantly higher in the quadrat at the sandy sea bottom in the juvenile settlement period, indicating that the magnitude of dominance by particular species was greater at the sandy sea bottom habitat. Our findings suggest that habitat connectivity affects the abundance and species richness of coral reef fishes, i.e. the isolated habitat was significantly more attractive for fishes than was the continuous habitat. Our findings also suggest that the main ecological factors responsible for organization of fish assemblage at a continuous habitat and at an isolated habitat are different.     

Microhabitat association and temporal stability in reef fish assemblages on massive <Emphasis Type="Italic">Porites</Emphasis> microatolls

A massive Porites microatoll generally has three types of microhabitat at the top, side, and base of the microatoll. The purpose of the present study was to analyze microhabitat associations of reef fish on microatolls to determine whether habitat characteristics play an important role in the structuring of reef fish assemblages in a patchy habitat. We also investigated temporal stability of reef fish assemblage structures over a period of 17 months to determine whether fish assemblage structures vary in a random manner. The results of correspondence analysis indicated species-specific habitat associations for pomacentrids (five species) and labrids (seven species). The degree of temporal stability of fish assemblage structures, calculated by Piankas index, was relatively high in a large-sized microatoll (0.503–0.831: 3.6m in diameter), in which microhabitat associations of fishes were clearly observed. The present study suggests that a microhabitat association is one of the important factors responsible for organization of reef fish assemblages in a microatoll.     

Importance of topography and soil texture in the spatial distribution of two sympatric dipterocarp trees in a Bornean rainforest

Relationships between spatial distributions and site conditions, namely topography and soil texture, were analyzed for two congeneric emergent trees, Dryobalanops aromatica and Dryobalanops lanceolata (Dipterocarpaceae), in a tropical rainforest in Sarawak, East Malaysia. A 52-ha permanent plot was divided into 1300 quadrats measuring 20m×20m; for each Dryobalanops species, the number and total basal area of trees 1cm in d.b.h. were compared among groups of quadrats with different site conditions. Because spatial distributions of both Dryobalanops and site-condition variables were aggregated, Monte-Carlo permutation tests were applied to analyze the relationships. Both single and multifactor statistical tests showed that the density and basal area distributions of the two species were significantly non-random in relation to soil texture and topographic variables. D.aromatica was significantly more abundant at higher elevations, in sandy soils, and on convex and steep slopes. In contrast, D.lanceolata preferred lower elevations and less sandy soils. In the study plot, there were very few sites (3 of 1150 quadrats tested) where the models of Hayashis method predicted the co-occurrence of the two species. These results suggest that between-species differences in habitat preferences are so large that they alone explain the spatially segregated distributions of these two species within the 52-ha study plot.     

Money-in-the-bank: a model for coral reef fish coexistence

Synopsis An alternative to the reef fish lottery model is proposed for explaining instances of coexistence of reef fishes without apparent spatial resource partitioning. This model is termed money-in-the-bank because of a financial analogy used to explain it. It stresses the importance of habitats that can support only one of two or more closely related species that coexist elsewhere. Populations living in such monospecific habitats could, according to the model, produce enough larvae to repopulate these habitats plus an excess that may settle in the multispecific habitats. Possible examples among cardinalfishes are given.This paper forms part of the proceedings of a mini-symposium convened at Cornell University, Ithaca, N.Y., 18–19 May 1976, entitled Patterns of Community Structure in Fishes (G. S. Helfman, ed.).     

A method for the investigation of those transformations under which the visual recognition of a given object is invariant

An experiment is described which shows in operation the program set out in Foster (1972a) for the investigation of the invariance transformations of visual recognition. The concern in the present study is with the Lie group of rotations SO(2), and a certain centrally located foveal Landolt ring. By presenting to the visual system this Landolt ring and a rotated image in rapid succession, one attempted to induce a specified rotation-type phi-motion. Two subjects were employed. Both reported the existence of the required type of phi-motion for rotations ₀ of the Landolt ring about the visual axis with -2/72/7. By appealing to the basic Proposition 2 of Foster (1972 a), the conclusion is reached that the visual system appears capable of effecting upon a certain centrally located foveal annulus the local 1-parameter group of rotations about the visual axis ₀, [–2/7,2/7].     

Status and habitat preferences of Uganda cheetahs: an attempt to predict carnivore occurrence based on vegetation structure

In this paper we examine whether the occurrence of cheetahs (Acinonyx jubatus) in Uganda can be predicted from habitat characteristics extracted from a vegetation map. We first established the status of the cheetah in Uganda through field-interviews that Gros conducted in 1990. Cheetahs occurred almost exclusively in the Karamoja region where we estimated 53–310 individuals. Based on 216 sightings, the average number of adults in all-adults sightings was 1.65 + SD 0.95 and the average number of cubs in family groups 2.5 + SD 1.65. Compared to Graham and Parker's 1965 East African survey, average adult group size was slightly smaller in 1990 and large family groups were rarer. Comparison with Gros 1990 survey showed considerably lower cub-to-adult ratio and percent of observations with cubs in Uganda than in Kenya. A Geographic Information System (GIS) analysis of vegetation structure in areas where cheetahs were observed and in those where none were reported suggested that cheetahs might favor habitats with 25–50% woody cover and grasses of medium height (50–100 cm). A discriminant analysis correctly classified 72.1% of used habitats and 70.4% of no-report habitats. A logistic regression analysis improved the correct allocation of used habitats by 2.2%. Either the discriminant function or the logistic regression, which require only four easily obtainable vegetation characteristics, may help to pinpoint suitable cheetah habitats for conservation purposes. Our approach could be adapted for analyzing habitat suitability for other species of carnivores.     

The supramolecular organization of red algal cell membranes and their participation in the biosynthesis and secretion of extracellular polysaccharides: a review

Summary The relationship between the supramolecular organization of red algal cell membranes and the biosynthesis and secretion of the cell wall skeletal and matrix polysaccharides is reviewed. Freeze-fracture studies have revealed that organized macromolecular structures — linear terminal complexes and tetrads — are present on the plasma membrane and on membranes of the endomembrane system. The linear terminal complexes seem to be involved in the biosynthesis, assembly, and orientation of the cellulose microfibrils and the tetrads in the synthesis of the matrix polysaccharides. It is shown how the research on the supramolecular organization of cell membranes has increased the knowledge on the biosynthesis and secretion of the extracellular crystalline and non-crystalline polysaccharides in red algae. In this review, the progress to date is discussed.Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

Amiprophos-methyl (APM): A rapid,reversible, anti-microtuble agent for plant cell cultures

Summary In plant cell suspension cultures sensitive to the herbicide amiprophos-methyl (APM), 1 to 3 M APM completely depolymerized both cortical and mitotic microtubule (MT) arrays in 1 hour. In comparison, a 2 hour application of 3 mM colchicine had no effect on MT arrays. Recovery from APM treatment occurred as early as 5 minutes after removal of APM. Short, cortical MTs were visible in 3 hours and complete MT arrays were found within 22 hours after drug removal.Sensitivity to APM-induced MT depolymerization varied according to species but was increased or decreased by varying the mitotic rate in cultures. The results indicated APM sensitivity was related to lowered stability of MT arrays in rapidly cycling cells. APM treatment may help distinguish stabilized cortical MTs in elongating cells and nonstabilized cortical MTs in rapidly dividing cells.Abbreviations MT microtubule - APM amiprophos-methyl - DMSO dimethyl sulfoxide - PBS phosphate buffered saline     

Spectral Sensitivity of the Hawaiian Saddle Wrasse, Thalassoma duperrey, and Implications for Visually Mediated Behaviour on Coral Reefs

Although tropical coral reefs are one of the most spectrally complex habitats, there is relatively little known about colour vision of reef fish. In this study, we measured the spectral sensitivity of an endemic Hawaiian coral reef fish, Thalassoma duperrey (family Labridae), and assessed the possible role of visual sensitivity in mediating intraspecific communication. Electrophysiological recordings of compound action potentials from retinal ganglion cells were used to generate spectral sensitivity curves for specific wavelengths (380–620nm). We found at least 2 sensitivity peaks for the on response (_max=460, 550nm). The off response lacked a short wavelength mechanism but a medium wavelength mechanism (_max=545nm) and a longwave mechanism (_max=570nm) were found. To quantify the visual stimulus provided by a conspecific individual, spectral reflectance from the colour pattern of T. duperrey was measured with a spectroradiometer. Luminance and spectral contrast were computed between colour patches of the pattern and between the patches and natural backgrounds (i.e., water and coral). Reflectance from the blue head and contrast from the blue, green and red patches matched the sensitivity maxima of T. duperrey, although this depended on the type of background. Our results indicate that T. duperrey should be able to visually detect the colour pattern of a conspecific fish and that T. duperrey's visual system is designed to enhance target detection in the coral reef habitat with matched and offset cone mechanisms.     

Immature erythroid cells with novel morphology and cytoskeletal organization in adultXenopus

Summary Nucleated erythrocytes of non-mammalian vertebrates are a useful model system for studying the correlation between changes in cell shape and cytoskeletal organization during cellular morphogenesis. They are believed to transform from spheres to flattened discs to ellipsoids. Our previous work on developing erythroblasts suggested that pointed cells containing incomplete, pointed marginal bands (MBs) of microtubules might be intermediate stages in the larval axolotl. To test whether the occurrence of such pointed cells was characteristic of amphibian erythrogenesis, we have utilized phenylhydrazine (PHZ)-induced anemia in adultXenopus. In this system, circulating erythrocytes are destroyed and replaced by erythroblasts that differentiate in the blood, making them experimentally accessible. Thus, we followed the time-course of morphological and cytoskeletal changes in the new erythroid population during recovery. During days 7–9 post-PHZ, pointed cells did indeed begin to appear, as did spherical and discoidal cells. The percentage of pointed cells peaked at days 11–13 in different animals, subsequently declining as the percentage of elliptical cells increased. Since degenerating old erythrocytes were still present when pointed cells appeared, we tested directly whether pointed ones were old or new cells. Blood was removed via the dorsal tarsus vein, and the erythrocytes washed, fluorescently tagged, and re-injected. In different animals, 2–8% of circulating erythrocytes were labeled. Subsequent to induction of anemia in these frogs, time-course sampling showed that no pointed cells were labeled, identifying them as new cells. Use of propidium iodide revealed large nuclei and cytoplasmic staining indicative of immaturity, and video-enhanced phase contrast and anti-tubulin immunofluorescence showed that the pointed cells contained pointed MBs. The results show that pointed cells, containing incomplete, pointed MBs are a consistent feature of amphibian erythrogenesis. These cells may represent intermediate stages in the formation of elliptical erythrocytes.Abbreviations MB marginal band - MS membrane skeleton - PHZ phenylhydrazine     

Segregation analysis in hereditary retinoblastoma

Summary Segregation analysis was performed on 211 nuclear families belonging to 166 pedigrees of hereditary retinoblastoma found in a number of series which have been gathered from the literature. Bilaterally affected carriers appear homogeneous. The segregation ratio in their offspring is 0.49, and the proportion of bilateral cases among affected offspring is 0.87. Both unilaterally affected and unaffected carriers appear heterogeneous. The very low segregation ratio (0.08) in the offspring of unilateral carriers who are not detected through an affected child, suggests the possiblity of two types of carriers, high and low transmitters. The proportions of low transmitters was estimated as 0.14 among all familial unilateral carriers and as 0.45 among all detected unaffected carriers. Unilateral and unaffected high transmitters give a significantly lower segregation ratio than bilaterally affected carriers.On the one hand, the existence of these two different types of carriers provides arguments in support of the hypothesis of delayed mutation. On the other hand, the differences in penetrance among high transmitters, according to their phenotype, supports the hypothesis of host resistance. Under the two-mutation hypothesis, the possibility that the mutation rate is variable among individuals and partly genetically determined, is suggested.     

The occurrence of HT-2 toxin and other trichothecenes in Norwegian cereals

A total of 449 grain samples, 102 barley, 169 wheat and 178 oat samples were collected from different regions of Norway from 1996–1998 crops, mainly from grain loads and silos. The samples were analysed for type A and B trichothecenes, the largest groups of mycotoxins produced by the Fusarium species, by gas chromatography with mass spectrometric detection (GC-MS). Factors affecting the presence of the different trichothecenes are discussed. Deoxynivalenol (DON) and HT-2 toxin were the trichothecenes most frequently detected, followed by T-2 toxin, nivalenol, and scirpentriol, scirpentriol being detected only in seven samples (>20 g/kg).Oats were the grain species most heavily contaminated with an incidence(% >20 g/kg) and mean concentration of positive samples of 70%(115 g/kg) for HT-2 toxin, 30% (60 g/kg) for T-2 toxin, 57%(104 g/kg) for DON, and 10% (56 g/kg) for nivalenol. The corresponding values for barley were 22% (73 g/kg), 5% (85 g/kg),17% (155 g/kg) and 6% (30 g/kg), and for wheat 1.2% (20 g/kg),0.6% (20 g/kg), 14% (53 g/kg) and 0% for HT-2, T-2, DON and nivalenol, respectively. Norwegian oats were found to contain HT-2 and T-2 toxin in concentrations that might be at threat to human health for high consumers of oats. The amount of DON was significantly lower than in the crop from previous years.This revised version was published online in October 2005 with corrections to the Cover Date.     

Nitrogen uptake and use of two contrasting maize hybrids differing in leaf senescence

In eastern Canada, the use of fertilizer N has been identified as the most energy-consuming component of maize (Zea mays L.) grain production. As the economic and environmental costs of excessive N fertilization rise, there is an increased emphasis on selection of hybrids with greater N use efficiency (NUE; defined as the ratio of the amount of ¹⁵N recovered in grain or stover dry matter to the amount of fertilizer ¹⁵N applied to the soil in this study). Using an ¹⁵N-labelling approach, a field study was conducted on a tile-drained Brandon loam soil (Typic Endoaquoll) on the Central Experimental Farm at Ottawa, Canada (45°22 N, 75°43 W) in 1993 and 1994. Fertilizer N uptake and partitioning within the plant in relation to dry matter changes were monitored during development of a current stay-green maize hybrid and an older early-senescing hybrid grown with three fertilizer N levels (0, 100, 200 kg N ha^-1). Dry matter, N concentration and¹⁵ N atom% enrichment of plant components were determined at five growth stages. The current stay-green hybrid, Pioneer 3902 had greater NUE than the old early-senescing hybrid, Pride 5, which was associated with 24% more dry matter production and 20% more N uptake during grain fill for Pioneer 3902. There was no indication of greater allocation of N to the grain in Pioneer 3902. Our data suggest that prolonged maintenance of green leaf area for photosynthate production during grain fill and the ability to take up available soil N later in grain filling are characteristics of maize hybrids with greater NUE.     

A novel pollen-specific α-tubulin in sunflower: structure and characterization

We describe here a new -tubulin isoform from sunflower we named -tubulin. -tubulin is the most divergent higher-plant -tubulin described so far, having an unusual deletion in the H1/B2 loop and a glutamine-rich C-terminus. We constructed a three-dimensional model and discuss its implications. Using specific antibodies, we show that -tubulin expression is restricted to the male gametophyte. -tubulin mRNA represents 90% of -tubulin mRNA and a small percentage of total pollen mRNA. Among the plants tested, -tubulin was only detected in sunflower and in Cosmos. Since both plants are Asteraceae, we propose that -tubulin is specific to this family. Our results suggest that -tubulin can inhibit tubulin assembly in pollen. This hypothesis is reinforced by the fact that -tubulin is found in a complex with -tubulin in mature sunflower pollen.     

Identification of a glutathione-S-transferase effector domain for inhibition of jun kinase, by molecular dynamics

We have recently found that the glutathione-S-transferase -isozyme (GST-), a cellular detoxification enzyme, potently and selectively inhibits activation of jun protein by its upstream kinase, jun kinase (JNK). This newly identified regulatory activity of GST- is strongly inhibited by a group of agents that inhibit its enzymatic activity. Since loss of enzymatic activity in general does not correlate with loss of regulatory activity, it is likely that inhibitor binding induces changes in the structure of one or more domains of GST that block its interaction with JNK. To identify regions of GST that change conformation on the binding of inhibitors, we have performed molecular dynamics calculations on GST- to compute its average structure in the presence and absence of the inhibitor, glutathione sulfonate. Superposition of the two average structures reveals that several regions change local structure depending upon whether the inhibitor is bound or not bound. Two of these regions, residues 36–50 and 194–201, are highly exposed. We have synthesized peptides corresponding to these two segments and find that the 194–201 sequence strongly inhibits the ability of GST- to block the in vitro phosphorylation of jun by JNK. These results suggest that this region of GST- is critical to its functioning as a newly discovered regulator of signal transduction.     

An Individual Based Model of the Impact of Suboptimal Habitat on Survival of the Grey Bush Cricket, Platycleis Albopunctata (Orthoptera: Tettigoniidae)

We developed an individual based model that investigates the importance of suboptimal habitats for the survival of the grey bush cricket Platycleis albopunctata living in a core habitat. Our model consists of two submodels. The first describes the demographic growth of the cricket known to mainly depend on temperature. The second introduces a simple heterogeneous habitat that consists of two areas of variable size and different suitability for reproduction. An optimal habitat is surrounded by a suboptimal habitat and both together are located within an unsuitable area. Applying Monte Carlo simulations we demonstrate that the extinction probability of a bush cricket population is significantly lower in an optimal habitat with a surrounding suboptimal habitat than without. Even small suboptimal habitats are sufficient to significantly reduce the extinction risk of the core population. For a bush cricket population living in a heterogeneous habitat mean minimum viable population estimates range from 13000 to 15000 adults, whereas 30000 adults are required for a population living in an optimal habitat without a surrounding suboptimal habitat. Thus, the presence of a suboptimal habitat can reduce minimum viable population by 50%. For any species, our model predicts that the type of dispersal between optimal and suboptimal habitat and the type of habitat selection determine whether suboptimal habitat is useful or detrimental for species persistence.     

Tandem mass spectrometry for characterization of unsaturated disaccharides from chondroitin sulfate,dermatan sulfate and hyaluronan

Fast atom bombardment tandem mass spectrometry has been used in the characterization of non-, mono-, di- and trisulfated disaccharides from chondriotin sulfate, dermatan sulfate and hyaluronan. The positional isomers of the sulfate group of mono- and disulfated disaccharides were distinguished from each other by both positive- and negative-ion fast atom bombardment tandem mass spectra, which gave sufficient information characteristic of the isomers. The anomeric isomers of nonsulfated disaccharides were characterized by the technique in the positive-ion mode. This fast atom bombardment collision induced dissociation mass spectrometry/mass spectrometry technique was also applied successfully to the characterization of trisulfated disaccharide.Abbreviations FABMS fast atom bombardment mass spectrometry - MI metastable ion - CID collision induced dissociation - MIKE mass analysed ion kinetic energy - SIMS secondary ion mass spectrometry - MS/MS mass spectrometry/mass spectrometry - HPLC high performance liquid chromatography - GlcA d-gluco-4-enepyranosyluronic acid - CS chondroitin sulfate - DS dermatan sulfate - HA hyaluronan - UA-GalNAc 2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-d-galactose - UA-GalNAc4S 2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-4-O-sulfo-d-galactose - UA-GalNAc6S 2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-6-O-sulfo-d-galactose - UA2S-GalNAc 2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-d-galactose - UA2S-GalNAc4S 2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-4-O-sulfo-d-galactose - UA2S-GalNAc6S 2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-6-O-sulfo-d-galactose - UA-GalNAcDiS 2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-4,6-di-O-sulfo-d-galactose - UA2S-GalNAcDiS 2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-4,6-di-O-sulfo-d-galactose - UA-GlcNAc 2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-d-glucose     

Quantitative measurement of cell-bubble attachment in bubble columns using foam flotation techniques

A simple and convenient system for quantitatively measuring the number of adsorbed animal cells per unit of bubble surface area (, unit: cells/cm2) was developed. The system was successfully applied to recombinant Chinese hamster ovary (r-CHO) suspension cultures to investigate the dynamic cell-bubble attachment in a bubble column. In serum-free medium, values increased with bubble rising height (H) and cell concentration (C) and then became constant (about 1750 cells/cm2) when H and C were sufficiently high. In medium containing protective additives, the trends of values with H were similar to that in serum-free medium. Compared with serum-free medium, polyvinyl-pyrrolidone (PVP) increased the values to 1941 cell/cm2 whereas other tested additives decreased the values of in some different degree.     

The structure of the incompatibility factors of Schizophyllum commune: Constitution of the three classes of B factors

Summary The B factors of Schizophyllum commune are of 3 classes: The high recombining class I has 7 alleles and 7 alleles; the low recombining classes are class II with 7 allels and probably 2 alleles and class III with probably 2 (or also 2) alleles and 7 allels. A fourth hypothetical class (-) was not found and either does not exist or is indistinguishable from class III by the tests employed. The and alleles differ from and by either (a) mutations affecting both mating specificity and recombination frequency, or (b) deletions involving most of the B region.The research was supported by a grant from the Atomic Energy Commission of the U.S. No. (30-1)-3875 and was performed at the Biological Laboratories, Harvard University, Cambridge, Mass., U.S.A.     

Potential Effects of Climate Warming on Fish Habitats in Temperate Zone Lakes with Special Reference to Lake 239 of the Experimental Lakes Area (ELA), North-Western Ontario

We used simple statistics (e.g. mean temperature, degree days, cumulative volume days) to describe present thermal habitats for cool water (yellow perch, Perca flavescens) and cold water (lake trout, Salvelinus namaycush) fish of a small boreal lake. We then modelled changes in the vertical and temporal extent of these habitats under various scenarios of climatic change that included increases in air temperature of 2°C, 4°C, and 9°C, and positive and negative deviations from present levels of 10% in solar radiation and relative humidity, and 20% in wind speed and the lake water extinction coefficient. Model simulations indicated pronounced changes in the temporal and vertical availability of fish thermal niche space. These changes were mainly driven by the large increases in mean mixed layer temperatures that corresponded to 85% of the increases in air temperature, but, in particular, changes in light attenuation also resulted in some non-linear, unexpected effects in the distribution and seasonal availability of thermal niche space. As expected, classical lake trout thermal habitat (5–15°C) was progressively reduced and almost disappeared in littoral areas in spring and early summer. Perch thermal niche space expanded for air temperature increases of up to 4°C, but largely disappeared for the 9°C increase. We discuss changes in thermal habitat with regard to the life history of lake trout and yellow perch, and include other determinants of fish habitat to evaluate the potential of these species for long-term ecological success under climatic warming.