Allomonal defence secretions of the American dog tick Dermacentor variabilis (Acari: Ixodidae) promote clustering

The release of the defence secretion from the large wax glands (sensilla sagittiformia) of Dermacentor variabilis ticks modifies the behaviour of other ticks by inducing clustering. A coating of natural tick secretion onto test objects (delipidized ticks, glass beads or filter paper discs) also elicits a clustering response, but a topically applied squalene, its major component, does not have this effect. The clustering response appears to be species specific: D. variabilis cluster on conspecific ticks that secreted but they fail to cluster on Amblyomma americanum or Ixodes scapularis ticks unless coated with secretions from D. variabilis. Volatile components in the defence secretion are involved in recruiting conspecific ticks to those that secreted. When attacked by predatory fire ants, Solenopsis invicta, D. variabilis clustered on individuals that had released the defence secretion. This suggests that the secretion protects ticks from predation by functioning as an alarm pheromone. If confirmed, this is the first report of an alarm pheromone and its glandular source in ticks. The terminology applicable to the integumental glands of ticks is discussed.     

Field experiments on the optical orientation of pelagic rotifers

Avoidance of shore by pelagic rotifers is considered to be the result of an optical orientation. Field experiments show that the spatial light distribution in the shore region determines the preferred direction of migration. The behaviour of Eudiaptomus gracilis was tested in comparison to that of rotifers.This publication is dedicated to Pater Dr. Josef Donner on the occasion of his 70th birthday     

Mictic patterns of the rotifer Brachionus plicatilis Müller in small ponds

Populations of the rotifer Brachionus plicatilis were monitored in three small ponds in a marsh on the Mediterranean coast. Samples were taken approximately every three weeks from July 1992 to November 1993. Salinity, temperature, conductivity, pH and oxygen concentration were measured in the field. Population density was determined from preserved quantitative samples. Individuals were classified as mictic females, amictic females, non-ovigerous females, and males, differentiating between two morphotypes (S and L). From these counts, a level of mixis was calculated. We also determined the proportion of mictic females in natural populations by culturing females isolated from fresh samples. From these data, mictic patterns over time and correlation between levels of mixis and environmental and population parameters were analyzed. From a previous study S and L morphotypes were known to correspond to genetically different clonal groups. Our data showed that reproduction was predominantly parthenogenetic in these clonal groups, but mictic females were found in most samples, the proportion of mictic females ranging from 0 to 29%. The clonal groups showed different patterns of mixis. L clonal group presented a continuous sexual reproductive pattern. In contrast, S clones showed a rather punctuated mictic pattern. A positive correlation between levels of sexual reproduction and population density was found for S and L groups. However, they differed in their density threshold for mictic reproduction. The adaptive meaning of these patterns and their implications in maintaining genetic diversity within and between populations are discussed.     

Linkage mapping of ‘25-kDa globulin’ genes on homoeologous group-1 chromosomes of bread and durum wheat

Acid polyacrylamide-gel electrophoresis (A-PAGE) of ethanol-soluble proteins from the endosperm of bread and durum wheats reveals some bands encoded by genes on the homoeologous group-1 chromosomes with higher mobility than the -gliadins. The isolation of these proteins showed that they were the previously described 25-kDa globulins encoded by genes at the Glo-A1, Glo-B1, and Glo-D1 loci. The variability found among a collection of 51 bread and 81 durum wheats was very low: two allelic variants at Glo-A1 and no variants at Glo-B1 in each of the two species, and two allelic variants at Glo-D1 in bread wheat. Inheritance studies of 25-kDa globulin genes on group-1 chromosomes of bread and durum wheat were carried out on the F₂ progeny from four crosses, two in bread wheat and two in durum wheat. The linkage mapping of the 1A 25-kDa globulin genes of bread wheat was done based on four prolamin loci: Glu-A1, Glu-A3, Gli-A1 and Gli -A3. The percentages of recombination and the distances found allowed a re-evaluation of the linkage map of endosperm protein loci on this chromosome. The Glo-A1 locus was found to be located at the distal end of the short arm of 1A chromosome, at a distance of 5.23±1.99 cM from Gli-A1, 6.85±2.22 cM from Glu-A3, 22.64±3.62 cM from Gli-A1, and at a recombination percentage of 49.30±4.40 from Glu-A1. A similar distance between Gli-A1 and Glo-A1 (4.82±1.75 and 6.66±2.26 cM) was found in durum wheat. The distance between Gli-D1 and Glo-D1 on chromosome 1D was 2.86±1.39 cM.     

Classification ofPythium ‘group F’ based on mycelial protein and isozyme patterns

Taxonomic characteristics were compared among 10 isolates ofPythium group F in tems of the electrophoretic patterns of their mycelial proteins and isozymes. These isolates were obtained from water of three ponds in different seasons and have an identical morphology of zoosporangia. Attempts to cross the isolates with each other themselves and with other isolates from the same group failed.Pythium group F is the most dominant of the pythia in the aquatic ecosystem and is difficult to identify because of the lack of sexual reproductive structures. Isozyme analysis proved useful in this respect. Comparisons of banding patterns of total soluble proteins and isozymes revealed five subgroups inPythium group F. Two isolates obtained from water of different ponds in different seasons showed the same protein and isozyme patterns. Our findings indicate that the use of total soluble protein and isozyme patterns for determining the variation withinPythium group F could become a valuable adjunct to the morphological and physiological criteria.     

Afferent bursting activity of ruff lateral line induced by background noise stimulation

Summary Single unit resting activities were recorded from fibres innervating a neuromast of the supra-orbital canal of the lateral line system of the ruff (Acerina cernua). The interval histogram of 1 of the 4 types of resting activity had a bimodal distribution (bursting activity). The resting activity of these fibres was compared with the measured vibration of the experimental table. The conclusion that the bursting activity is not spontaneous but is caused by small background vibrations of the table was supported by recording of extracellular hair cell responses.Abbreviation ISI Interspike interval     

The wise use of wetlands: identifying development options for Ghana's coastal Ramsar sites

The Government of Ghana has recently declared five coastal wetlands to be Ramsar sites. This requires the wise use of wetlands of international importance for bird habitat, but does not preclude human habitation or ecologically friendly development. The sites are Muni-Pomadze, Densu Delta, Sakumo, Songor and Keta. An attempt was made to identify and assess a range of development options for initiation within the sites that would be compatible with the environmental concerns of Ramsar, while also being technically and economically viable and socially acceptable to the communities in the sites. The appraisal included developing a detailed understanding of the physical, biological, human and institutional resources of the areas, the land uses and prevailing livelihood systems of local people, and the pressures placed on the natural resources of the wetlands. Many of the developments nominated by stakeholders were rejected, but twenty topics passed the initial tests. These were considered in more detail using information collected for the study by national specialists. Most of the options were considered suitable for local level implementation by community groups or local entrepreneurs. Government assistance will be needed to ensure an enabling institutional framework for small-scale business development is provided.     

The giant neurone system in ophiuroids

Summary The radial nerve cords of members of the class Ophiuroidea consist of two parts, the ectoneural and the hyponeural tissues, which are separated by an acellular basal lamina. The hyponeural tissue is composed entirely of motor fibres. The cell bodies of the hyponeural neurones are arranged in ganglia, one to each segment of the arm, and each containing approximately one hundred cell bodies. Synaptic contact between the two tissues occurs across the basal lamina. Ultrastructural evidence shows that the majority of these synapses operate in the ectoneural to hyponeural direction. Three pairs of nerve bundles, each containing approximately thirty five large motor fibres arise from each ganglion and innervate the intervertebral muscles. The large motor fibres divide into a number of pre-terminal axons in the region in which the motor fibre enters the muscle block. The terminal axons run at right-angles across the muscle fibres and neuromuscular junctions are found at the points of contact between the two; each terminal axon makes contact with a large number of muscle fibres. The hyponeural axons also pass through the juxtaligamental tissue before they reach the muscle blocks and there is some evidence of synaptic contact with the juxtaligamental cells. The juxtaligamental tissue is thought to be associated with changes in the structural properties of the collagenous ligaments of the arm during arm autotomy (Wilkie 1979). Degeneration studies confirmed the layout of the hyponeural motor axons.     

Amelanchier alnifolia vegetation in eastern Idaho,USA and its environmental relationships

Fifteen shrub stands of Amelanchier alnifolia vegetation were studied using Braun-Blanquet procedures, tabulated, and ordered by Twinspan, Decorana, and field experience into 5 groups of stands. The stands occurred on the lower slopes of the southwestern Teton and southeastern Big Hole mountains of eastern Idaho and in-and outside a U.S. Forest Service exclosure above the Hoback River in adjacent Wyoming. The ecology of this Amelanchier vegetation as a whole and of the 5 groups of stands is discussed using Jenny's factors of soil formation (1941, 1958, 1980) as a framework. Plant indicator values (Ellenberg 1979, 1988) which rank species on their occurrences in relation to light, temperature, continentality of climate, water availability, soil reaction (pH), and soil nitrogen supply, were independently assigned to the 121 species of vascular plants encountered in the described stands.     

Normal coordinate analysis of 2′-deoxythymidine and 2′-deoxyadenosine

The proposed valence force field allows us to reproduce the vibration modes of 2-deoxythymidine and 2-deoxyadenosine. The present calculations are based on the Wilson GF-method and a non-redundant set of symmetrical coordinates. The calculated wavenumbers have been compared to the available Raman and infrared peak positions observed in solid, amorphous or aqueous samples. Moreover, the results obtained with the present force field allow us to assign some of the characteristic vibration modes for the thymidine and adenosine residues involved in DNA double-helical chains.     

Chitovibrin: a chitin-binding lectin fromVibrio parahemolyticus

A novel 134 kDa, calcium-independent chitin-binding lectin, chitovibrin, is secreted by the marine bacteriumVibrio parahemolyticus, inducible with chitin or chitin-oligomers. Chitovibrin shows no apparent enzymatic activity but exhibits a strong affinity for chitin and chito-oligomers >dp9. The protein has an isoelectric pH of 3.6, shows thermal tolerance, binds chitin with an optimum at pH 6 and is active in 0–4m NaCl. Chitovibrin appears to be completely different from other reported Vibrio lectins and may function to bindV. parahemolyticus to chitin substrates, or to capture or sequester chito-oligomers. It may be a member of a large group of recently described proteins in Vibrios related to a complex chitinoclastic (chitinivorous) system.Abbreviations (GlcNAc)₂ N,N-diacetylchitobiose - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - PTS phosphotransferase system     

Unification of two methods for measuring the amount of nitrogen fixed by a legume crop

Summary Two methods for measuring nitrogen fixation, the so-called A value method and the so-called isotope dilution or substrate labelling method are shown to be both unifiable and yield independent.     

Promotion of murine antitumour activity by prothymosin α treatment: I. Induction of tumoricidal peritoneal cells producing high levels of tumour necrosis factor α

Summary The effect of prothymosin (ProT) on the survival of DBA/2 mice inoculated with syngeneic tumour cells was studied. DBA/2 mice inoculated intraperitoneally (i.p.) with 2×10⁵ syngeneic leukaemic L1210 cells developed ascites within 8–12 days and died 10–14 days later. Treatment with ProT consistently inhibited the development of ascites in 20% of the treated animals and prolonged the survival of 40%–60% of the animals up to 70 days. The most effective treatment schedule of ProT was 300 ng/mouse given i.p. at 2-day intervals for 3 weeks followed by a rest period of 7 days, prior to tumour cell inoculation. Peritoneal exudate (PE) cells collected from mice treated with the optimal dose of ProT produced, in the absence of exogenous stimulus, six- to eightfold higher levels of tumour necrosis factor (TNF) than PE cells from control mice. Furthermore these cells exhibited cytotoxic activity against several tumour cell lines including the syngeneic L1210, the TNF-insensitive P815 mastocytoma, the human MOLT-4 lymphoblastic leukaemia, as well as the murine TNF-sensitive L929 fibroblast cell line. Kinetic studies revealed that both production of TNF and tumoricidal activity peaked 7 days after the last injection of ProT and were maintained at high levels over a period of 1 month. Injections with 150 ng ProT slightly improved the survival of mice whereas higher (500 ng and 1000 ng) doses of ProT and a wide range of thymosin 1 doses remained without any effect. PE cells collected from these mice produced extremely low levels of TNF and exhibited negligible tumoricidal activity. Our data demonstrate that ProT has a protective effect in vivo against the growth of adoptively transfered tumour cells and suggest that this effect is, at least in part, mediated by ProT-activated PE cells. These cells were demonstrated to produce high levels of TNF in vitro and to exhibit activity against both TNF-sensitive and TNF-resistant cell lines.Supported by a CEC grant to Dr. M. Papamichail     

Behavioral responses of a leaf beetle to injury-related changes in its salicaceous host

Summary Adults of the leaf beetle Plagiodera versicolora Laich, avoided previously injured shoots of Salix alba Tristis in favor of nearby uninjured ones. The response was rapid and persisted for five days of study. During brief periods of observation, the vast majority of beetles engaged in behaviors other than locomotion such as feeding and resting. Furthermore, the proportions of beetles walking were similar on injured and uninjured shoots. It appears that under these experimental conditions previous injury did not greatly increase searching behavior of the beetles. Leaves on previously injured shoots received less subsequent herbivory than uninjured ones. Findings of these experiments are consistent with patterns of herbivory observed in the field and known reproductive responses of beetles to diets of injured leaves. These results provide new information toward understanding relatively low levels of herbivory on individual willow leaves associated with the feeding of P. versicolora.     

Are biodiversity ‘hotspots’ correlated with current ecoclimatic stability? A pilot study using the NOAA-AVHRR remote sensing data

The GAC (Global Area Coverage) by the NOAA-AVHRR satellites represents an excellent data set for studying global and regional patterns of variations in surface conditions driven in part by climatic variation. In this pilot study we examined whether biodiversity hotspots, defined from peak concentrations of neoendemics as well as geographically relict forms, differ in ecoclimatic stability from surrounding areas under present-day climatic conditions. Coefficients of variation of the ratio between brightness surface temperature (Ts) and the Normalized Difference Vegetation Index (NDVI) based upon 10 years' monthly composited scenes of tropical Africa revealed distinctive geographical patterns of interannual variability in surface conditions. Regions with a predominance of old species are characterized by spatial uniformity in the ecoclimatic variability, while regions where rapidly radiating groups dominate are spatially complex in this respect. However, the exact hotspots, with peak concentrations of endemic species, are characterized by a local reduction in ecoclimatic variability, or placement on the boundary to a stable region. This relationship was supported statistically by comparing ecoclimatic profiles across montane forests representing hotspots, and those of other montane forests. It is suggested that, because of interactions between prevailing atmospheric flows, topography and vegetation, the impact of extreme weather is moderated locally. The correlation between current stability and aggregates of neoendemics as well as old relics indicate that local moderation of climatic extremes persist through shifting climatic periods, permitting populations of unique species to survive in these places. The results are used to identify study sites for better ground truthing and for paleoclimatological studies which may be useful for more thorough studies of these relationships.     

Sun-compass orientation in the characidCheirodon pulcher

Synopsis Small microcharacidsCheirodon pulcher were netted during the dry season in pools of the savanna llanos at a considerable distance from the main river channel. Fish could have moved from the river to these pools using sun-compass orientation. Orientation responses of these fish were tested in a four-armed experimental device, exposed to direct sunlight or to azimuth-inverted sunlight reflected by a mirror. Groups of 20 fish were placed in a central area, released and then counted in the arm traps. When exposed to direct sunlight, fish oriented south, both in the morning and afternoon. Nevertheless, when the sun azimuth was inverted they oriented north, indicating that they use a sun-compass and that they compensate for sun-azimuth inversion at noon in a way that geographic headings remain constant throughout the day. These results reinforce previous laboratory interpretations which suggested that these flood plain species migrate inland during the high-water period and return to the main river channels before the dry season begins.     

Induction of Somatic Embryogenesis and Plant Regeneration of ‘Ataulfo’ Mango (Mangifera indica)

Nucellar explants from the immature fruit of Ataulfo mango, 3–4 cm long, were used. The process had a very low efficiency (<10%); however, Ataulfo was more embryogenic than other cultivars such as Tommy Atkins or Haden in our hands. Overall, the process from nucellus to plantlet stage took 5 months. Twelve regenerated plants were obtained and are currently growing in the greenhouse. They appear to be normal and free of abnormalities. Some biochemical and molecular tests are currently being carried out.     

Occurrence of phytoalexins and other putative defense-related substances in uninfected parsley plants

Considerable amounts of the following substances were found in uninfected parsley (Petroselinum crispum) cotyledons: furanocoumarins, the putative phytoalexins of this and some related plant species, two enzymes of the furanocoumarin pathway (S-adenosyl-L-methionine: xanthotoxol and S-adenosyl-L-methionine: bergaptol O-methyltransferases), two hydrolytic enzymes (1,3--glucanase, EC 3.2.1.39, and chitinase, EC 3.2.1.14), and pathogenesis-related proteins. The furanocoumarins and the methyltransferase activities reached their highest levels at the onset of cotyledon senescence as the hydrolytic enzymes increased from low to relatively high activity values. The relative amounts of pathogenesis-related proteins 1 and 2, as well as the corresponding mRNAs, also increased markedly. Two enzymes of general phenylpropanoid metabolism, L-phenylalanine ammonia-lyase and 4-coumarate: CoA ligase, decreased in activity in a biphasic fashion during cotyledon development. At all developmental stages, the levels of these putative defense-related agents in total cotyledon extracts were too high to enable detection of, possibly, additional changes upon infection with zoospores of Phytophthora megasperma f. sp. glycinea, a fungal pathogen to which parsley shows a non-host, hypersensitive resistance response.Abbreviations BMT S-adenosyl-L-methionine: bergaptol O-methyltransferase (EC 2.1.1.-) - 4CL 4-coumarate: CoA ligase (EC 6.1.1.12) - CMT S-adenosyl-L-methionine: caffeate O-methyltransferase (EC 2.1.1.-) - PAL L-phenylalanine ammonia-lyase (EC 4.3.1.5) - PR pathogenesis-related - XMT S-adenosyl-L-methionine: xanthotoxin O-methyltransferase (EC 2.1.1.-)     

Chromosome and isoenzyme studies on cells derived from protoplast fusion of Nicotiana glauca with glycine max-Nicotiana glauca cell hybrids

Summary The somatic hybrids of Glycine max (L)Merr.-Nicotiana glauca Grah. exhibited a preferential loss of N. glauca chromosomes. When protoplasts from such hybrid cells were back fused twice to N. glauca protoplasts, a considerable increase in stability of the N. glauca chromosomes was observed. Gel electrophoresis studies of aspartate aminotransferase showed that the chromosome(s) responsible for this enzyme was stabilized in the back fused hybrid cell lines. The data suggest that the back fusion technique described in this study might aid in stabilizing somatic hybrids.NRCC No. 18040