Structural Aspects of the Lichen-Rock Interface Using Back-scattered Electron Imaging

The profound knowledge of the structural and chemical characteristics of the interface between lichen thallus and rock, seems to be indispensable for the process of understanding the lichen symbiosis as well as the significance of the weathering action of lichens. One of the most promising techniques to be used in this investigation is the Scanning Electron Microscopy (SEM) in the back-scattered electron (BSE) emission mode. In the present work thalli of Parmelia conspersa, Aspicilia intermutans and Lecidea auriculata growing in granitic rock were examined by SEM in BSE mode with (Energy Dispersive Spectroscopy) EDS. In the case of the foliose thalli the observation of the interface permits detection of the rhizine/hyphae adherence and determination of the origin of the minerals which adhere to the rhizine/hyphae. In the case of the crustose thalli BSE permits investigation within the ultrastructure of the crustose thallus and crustose lichen-rock contact zone and also allows observations of the penetration and filling of the fissures and cracks of the underlying rock by components of the thallus and other living organisms. The BSE images could contribute to a better knowledge of the cytological state of the rock-inhabiting organisms and also to the understanding of the action of the chemical treatments used in the removal of lichen from building materials.     

Heterogeneity of Chlorophyll Fluorescence over Thalli of Several Foliose Macrolichens Exposed to Adverse Environmental Factors: Interspecific Differences as Related to Thallus Hydration and High Irradiance

Spatial heterogeneity of chlorophyll (Chl) fluorescence over thalli of three foliose lichen species was studied using Chl fluorescence imaging (CFI) and slow Chl fluorescence kinetics supplemented with quenching analysis. CFI values indicated species-specific differences in location of the most physiologically active zones within fully hydrated thalli: marginal thallus parts (Hypogymnia physodes), central part and close-to-umbilicus spots (Lasallia pustulata), and irregulary-distributed zones within thallus (Umbilicaria hirsuta). During gradual desiccation of lichen thalli, decrease in Chl fluorescence parameters (F_O - minimum Chl fluorescence at point O, F_P - maximum Chl fluorescence at P point, ₂ - effective quantum yield of photochemical energy conversion in photosystem 2) was observed. Under severe desiccation (>85 % of water saturation deficit), substantial thalli parts lost their apparent physiological activity and the resting parts exhibited only a small Chl fluorescence. Distribution of these active patches was identical with the most active areas found under full hydration. Thus spatial heterogeneity of Chl fluorescence in foliose lichens may reflect location of growth zones (pseudomeristems) within thalli and adjacent newly produced biomass. When exposed to high irradiance, fully-hydrated thalli of L. pustulata and U. hirsuta showed either an increase or no change in F_O, and a decrease in F_P. Distribution of Chl fluorescence after the high irradiance treatment, however, remained the same as before the treatment. After 60 min of recovery in the dark, F_O and F_P did not recover to initial values, which may indicate that the lichen used underwent a photoinhibition. The CFI method is an effective tool in assessing spatial heterogeneity of physiological activity over lichen thalli exposed to a variety of environmental factors. It may be also used to select a representative area at a lichen thallus before application of single-spot fluorometric techniques in lichens.     

Modulation of natural killer activity by thymosin alpha 1 and interferon

Summary A single injection of -interferon (-IFN) (30 000 units/mouse), a major biological modifier of natural killer (NK) cytolytic activity, strongly stimulated NK activity in normal mice, as expected, while the same treatment did not statistically alter the NK response in cyclophosphamide (CY)-suppressed animals.We investigated the possibility of thymosin ₁ cooperating with -IFN in boosting NK activity in CY-suppressed animals.The results show that treatment with thymosin ₁ (200 g/kg) for 4 days, followed by a single injection of -IFN 24 h before testing, strongly restored NK activity in CY-suppressed mice. Thymosin ₁ was, moreover, able to accelerate the recovery rate of NK activity in bone marrow reconstituted murine chimeras.Taken together the data support the concept that the synergic effect between thymosin ₁ and -IFN could be the result of effects on differentiation of the NK lineage at different levels.     

Net photosynthetic response patterns of the basidiomycete lichen Cora pavonia (Web.) E. Fries from the tropical volcano La Soufrière (Guadeloupe)

Summary The response of net photosynthesis to temperature, moisture, and light was examined in thalli of the tropical basidiomycete lichen Cora pavonia from recent lahar flows on the volcanic summit La Soufrière (Guadeloupe, French West Indies). Although thalli of C. pavonia are typically exposed to only low light intensities and isothermal temperature conditions under prevailing cloud/shroud conditions on La Soufrière, their photosynthetic response matrix reveals an unexpected breadth of response. The temperature optimum of net photosynthetic uptake in C. pavonia rises from 6°C at a photon flux area density of 25 mol m^–2 s^–1 PAR to 27°C at 1000 mol m^–2 s^–1 PAR, with rates of maximal net photosynthetic uptake exceeding 25 mg CO₂ g^–1 h^–1. Net photosynthesis was optimal at thallus moisture contents of 250 to 350 percent water content by weight, declining only slightly in fully saturated thalli. These response patterns pose an apparent paradox, as on most days they will act to severely restrict net photosynthetic uptake by thalli of C. pavonia on La Soufrière. This paradox is discussed in context of those selective pressures faced by lichen thalli in later successional stages as well as those imposed by brief periods of atypical weather conditions.     

Summer egg production rates of paracalanid copepods in subtropical waters adjacent to Australia's North West Cape

The biological oceanography of waters adjacent to Australia's North West Cape (21° 49 S, 114° 14 E) was studied during the austral summers of 1997/98 and 1998/99. We measured egg production rate (EPR) by the small paracalanid copepods that dominated the calanoid community. Bottle incubation experiments were conducted at a shallow (20 m) station in the mouth of Exmouth Gulf, and at a shelf-break station (80 m). In 1997/98, we measured EPR by Paracalanus aculeatus, P. indicus, Acrocalanus gracilis and Bestiolina similis, but in 1998/99, we concentrated on P. indicus. Maximal observed EPRs by Paracalanus and Acrocalanus species were 30 eggs female^–1 d^–1, but B. similis attained only 17 eggs female^–1 d^–1. Sporadic measurements of EPR by P. aculeatus minor (maximum 4 eggs female^–1 d^–1) and Parvocalanus crassirostris ( 9 eggs female^–1 d^–1) were also made. However, maximal EPRs were seldom achieved and were often less than 10 eggs female^–1 d^–1. There was no difference between EPR of either P. indicus or B. similis in 1997/98 and 1998/99, despite differences in temperature. Trophic resources severely limit copepod egg production in this area. We suggest that variability and skewness of egg production data derived from individual incubations may be used to judge the degree of food limitation of the population and the variability in feeding success between individuals. The dominance of small copepods and the invariance in their EPR suggest that pulses in physical forcing and subsequent primary production will be severely damped by trophodynamic processes before reaching larval fish.     

The effect of parental condition on egg-size and reproductive success in short-tailed shearwaters Puffinus tenuirostris

Eggs were exchanged between 50 pairs of shorttailed shearwaters Puffinus tenuirostris on Great Dog Island, Bass Strait, Australia, in an attempt to distinguish the intrinsic effects of egg-size from any effects stemming from differential quality of parental care. At 64 experimental nests, large and small eggs were exchanged whereas at 36 control nests, eggs of equivalent, medium, size were exchanged. Egg-size appeared independent of maternal effects. In both groups, hatching and fledging success were independent both of eggsize and of the body condition of the attending parents. This suggests that breeding success in these birds may be more closely related to the behavioural traits of parents than to physiological factors.     

Moisture content and CO2 exchange of lichens

Summary Net photosynthesis (10 klx light intensity, 150 E m^-2 s^-1 PAR) and dark respiration of the lichen Ramalina maciformis at different temperatures are measured in relation to thallus water content. Both first increase with increasing hydration. Dark respiration then remains constant with increased water content until thallus saturation. In contrast, a further increase in water content leads to a depression of net photosynthesis, as shown in previous studies, after a maximum of CO₂ uptake has been attained. However, the extent of this depression depends strongly on temperature. In saturated thalli (160% water content in relation to lichen dry weight) the depression amounts to about 15% and 63% of the maximum unsaturated rate at 5°C and 25°C thallus temperature, respectively. The moisture compensation-point of net photosynthesis is also decisively determined by temperature (for 0°C at 20% water content; for 25°C at 15%), and the water content that allows maximum rates of CO₂ uptake (for 0°C at 80%; for 25°C at less than 40% water content). An electrical analogue of CO₂ exchange in a lichen thallus is presented, and it is suggested that the experimental results may be interpreted in terms of temperature-dependent CO₂ diffusion resistances in imbibed lichen thalli.     

Does “ring syndrome” exist? An analysis of 207 case reports on patients with a ring autosome

Summary Analysis of 207 case reports on patients with ring autosome showed that: (1) Forty patients, a fifth of the total, had extreme growth failure together with an otherwise almost-normal appearance, viz. no major malformation, no specific deletion syndrome, no or only a few unspecific minor anomalies. This phenotype may be regarded as the ring syndrome, a term proposed by Cote et al. (1981) since it is independent of what chromosome is involved. (2) Severe growth failure, the sole major physical abnormality in the ring syndrome, was seen significantly more often among patients with ring of larger chromosomes than among patients with a smaller ring, indicating that the greater the chromosome involved in ring formation, the higher is the probability of severe growth failure. (3) Larger ring chromosomes showed significantly more often instability than smaller rings, suggesting that there may be a correlation between ring instability and the size of the chromosome involved. (4) Growth failure was present in significantly more patients with a labile ring than with a stable ring, indicating that a correlation may exist between ring instability and growth failure. It is suggested that the ring syndrome observed in many cases with ring autosome may result from end-to-end fusion of chromosome ends, an event not involving deletion in the genetic sense. It is also suggested that the ring syndrome is caused by a continuous generation of secondary aneuploid cells with increased mortality, i.e. structural ring instability which seems to be a function of the size of the chromosome involved. Thus, formation of a ring chromosome in certain cases might be regarded as a structural mutation, i.e. an alteration in the structure of the genetic material per se, rather than a loss or gain of genetic dosages.     

Regional distribution of membrane-bound γ-glutamyl transpeptidase activity in mouse brain

Activity of membrane-bound -glutamyl transpeptidase (-GTP) was examined in various regions of mouse brain, in capillaries of the cerebral cortex and in telencephalic choroid plexuses. The level of activity in the capillaries was double and that of the choroid plexus nine times that of the -GTP activity found in the brain, septum, hippocampus, hypothalamus, thalamus, cerebellum, frontal cortex, pons, medulla oblongata, and amygdala. Histochemically the -GTP activity was demonstrated in the surface membranes of choroidal cells and in the endothelium of small capillaries.The activities of -GTP of cerebral cortex, choroid plexus, and capillaries from rabbit were 5–17 times greater than those from corresponding areas of mouse brain. While 30 mM methionine stimulated (in vitro) the enzyme from mouse brain, no such effect was observed with the enzyme activity from rabbit brain. The -GTP activity from the capillaries of cerebral cortex of both mouse and rabbit was not effected by the presence of methionine.These findings suggest existence of differences in the specificity of -GTP activity in these two species.     

Die Kultur der Erdflechte Endocarpon pusillum im Labor

Zusammenfassung Kulturversuche mit der Erdflechte Endocarpon pusillum im Labor bestätigen die oft angezweifelten Beobachtungen und Ergebnisse von Stahl (1877). Eine reproduzierbare Kultur dieser Flechte im Labor von Spore zu Spore ist möglich. Bereits nach zwei Monaten läßt sich eine Differenzierung in Rinde, Algenschicht, Mark und Rhizinen erkennen; nach 5-6 Monaten sind reife, keimfähige Ascosporen vorhanden.Beobachtungen bei der Sporengewinnung zeigten, daß die Ascosporen bis zu einer Höhe von 5 cm ausgeschleudert werden. Der Sporenabschuß kann dabei mehrere Tage anhalten und zu dichten Sporenaussaaten führen.Die Thallusentwicklung (Keimung der Ascosporen, Umwandlung der Hymenialgonidien in Thallusgonidien, Bildung von Thallusinitialen, Prothalli und Primärthalli) und die Bildung reifer Perithecien mit keimfähigen Sporen in Laborkulturen wird beschrieben und abgebildet.Die Frage der speziellen Eignung schnellwüchsiger kleiner Erdflechten für die Laborkultur und das Problem der Flechtensynthese wird diskutiert.

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The culture of the lichen Endocarpon pusillum in the laboratory

Summary Culture experiments with the lichen Endocarpon pusillum corroborate the often doubted observations and results of Stahl (1877). It is possible to cultivate this lichen in the laboratory from spore to spore. After two months a differentiation into cortex, algae-layer, medulla and rhizines is developed and after 5–6 months the formation of mature and germinable ascospores is finished.Observations of the spore dispersal showed that the ascospores are ejected up to 5 cm. The spore dispersal can endure for some days and in this way produces a compact dissemination.The thallus development (germination of ascospores, transformation of hymenialalgae into thallus-algae, development of thallus initials, prothalli and primary thalli) and the formation of mature perithecia with germinable ascospores in laboratory cultures is described and illustrated.The opinion that such quickly growing and developing epigaeic lichens are especially suitable for laboratory cultures is emphasized and the problem of lichensynthesis is discussed in relation to the results of the experiments.

     

Hydrolase-catalyzed β-mannosylations

Transmannosylations catalysed by -mannosidase from snail viscera or -galactosidase from Aspergillus oryzae were accomplished with 4-nitrophenyl D -mannopyranoside as donor substrate. With suitable hydrophobic acceptor molecules preferentially 1-4-linked disaccharides were obtained. The activities of both glycosidases in buffer cosolvent mixtures were determined, and conditions for their immobilization were elaborated and optimized. A model of the enzymic transfer mechanism is suggested.     

Chemical and gelling profile of ice-ice infected carrageenan from Kappaphycus striatum (Schmitz) Doty “sacol” strain (Solieriaceae, Gigartinales, Rhodophyta)

The occurrence of ice-ice disease in farmedKappaphycus spp. has tremendous implication on thecarrageenan industry in the Philippines. To elucidate the effect of thisdiseaseon the carrageenan quality, the chemical profile of carrageenan extracted fromhealthy and diseased Kappaphycus striatumsacol strain, was investigated using ¹³C and¹H NMR, FT-IR and GPC methods of analysis. The native carrageenanextracts were composed predominantly of kappa carrageenan with trace amounts ofiota and 6-O-methylated carrageenan. Structural evidence indicatesdepolymerization of carrageenan from the ice-ice infectedportion of the thallus (whitish and soft part) lowered levels of iota andmethylconstituents. This finding was correlated to its low number average molecularweight (30 kDa) value. Accordingly, appreciable decreases incarrageenan yield, gel strength and viscosity and increase in syneresis indexwere noted. On the other hand, archetype quality of kappa-carrageenan wasobserved from both healthy and uninfected portion of the diseased thalli.     

Surface hydrophobicity causes SO2 tolerance in lichens

BACKGROUND AND AIMS: The superhydrophobicity of the thallus surface in one of the most SO(2)-tolerant lichen species, Lecanora conizaeoides, suggests that surface hydrophobicity could be a general feature of lichen symbioses controlling their tolerance to SO(2). The study described here tests this hypothesis. METHODS: Water droplets of the size of a raindrop were placed on the surface of air-dry thalli in 50 lichen species of known SO(2) tolerance and contact angles were measured to quantify hydrophobicity. KEY RESULTS: The wettability of lichen thalli ranges from strongly hydrophobic to strongly hydrophilic. SO(2) tolerance of the studied lichen species increased with increasing hydrophobicity of the thallus surface. Extraction of extracellular lichen secondary metabolites with acetone reduced, but did not abolish the hydrophobicity of lichen thalli. CONCLUSIONS: Surface hydrophobicity is the main factor controlling SO(2) tolerance in lichens. It presumably originally evolved as an adaptation to wet habitats preventing the depression of net photosynthesis due to supersaturation of the thallus with water. Hydrophilicity of lichen thalli is an adaptation to dry or humid, but not directly rain-exposed habitats. The crucial role of surface hydrophobicity in SO(2) also explains why many markedly SO(2)-tolerant species are additionally tolerant to other (chemically unrelated) toxic substances including heavy metals.     

Location by fluorescence microscopy of glycosidases and a xylanase in the anaerobic gut fungi Caecomyces communis,Neocallimastix frontalis,and Piromyces rhizinflata

-d-Glucosidase, -d-fucosidase -d-xylosidase, and -cellobiopyranosidase activities in Caecomyces communis, Neocallimastix frontalis, and Piromyces rhizinflata, located with fluorescent conjugates, occur throughout the whole thallus as from zoospore germination and disappear before sporulation. -d-Galactosidase and -l-arabinopyranosidase activities are low or nonexistent. A xylanase, detected by indirect immunofluorescence, was observed at the surface of the vegetative cells, vesicles, or rhizoids. Cross-reactions prove the existence of analogies in structure among the enzymes of these anaerobic gut fungi.     

QUANTITATIVE VARIATION IN VULPINIC AND PINASTRIC ACIDS PRODUCED BY TUCKERMANNOPSIS PINASTRI (LICHEN-FORMING ASCOMYCOTINA,PARMELIACEAE)

Tuckermannopsis pinastri is a lichen species found commonly on rocks and tree branches in boreal and alpine habitats in the northern United States. Members of this species produce three yellow-pigmented phenolic compounds: usnic, pinastric, and vulpinic acids. The objective of our study was to quantify the variation in concentration of the latter two of these compounds in relation to substrate factors, chlorophyll content, and thallus size. Using high-performance liquid chromatography, we analyzed 120 thalli of T. pinastri collected randomly from a single large population located at Spruce Knob, West Virginia. Although individuals were sampled from both tree and rock substrates that differed markedly in light intensity, these environmental factors were not correlated with observed variations in vulpinic or pinastric acid concentrations. Instead, compound concentrations were correlated most closely with thallus size, with small rather than large thalli having the highest concentrations of the two compounds. Small thalli did not have higher concentrations of chlorophylls than large thalli, however, which suggests that the rate of production of secondary compounds by the fungus in T. pinastri is independent of algal biomass. Inasmuch as lichen secondary compounds serve a defensive role against microorganisms and herbivores, our results suggest that small, juvenile thalli are better defended than more mature thalli.     

Neuronal responses in the tectum opticum ofSalamandra to visual prey stimuli

Summary In the tectum opticum ofSalamandra salamandra neurons were recorded that showed different selectivity to visual prey stimulus parameters. 21 of 80 neurons responded stronger to rectangles oriented horizontally (wormlike configuration) than to the same patterns oriented vertically. With increasing stimulus velocity, however, these neurons showed non-uniform response characteristics. Although there are partial similarities between behavior and neuronal activity, no response curve of tectal neurons corresponds strictly to response curves of salamander preycapture behavior. So none of the neuron types can be called a prey detector.Supported by the Deutsche Forschungsgemeinschaft     

Immimocytological localization of a somatostatin-like substance in the brain of the giant slug,Limax maximus L.

Summary Immunocytological tests reveal the presence of a somatostatin-like substance in perikarya and axons in the brain of the giant slug Limax maximus L. Controls carried out on adjacent sections with absorbed antiserum or different antibodies raised against several biologically active peptides of vertebrates (ACTH-17-39, - and endorphin, - and MSH, methionin-enkephalin, TRH) demonstrate the specificity of the staining. However, some cells are both somatostatin- and FMRF-amide-positive. In the cerebral ganglia, the right Z-area cells, responsible for the synthesis of the maturation hormone (MH) are strongly somatostatin-positive. These results suggest a similarity between the MH and the somatostatin-like material contained in the Z-area cells. The simultaneous presence of two peptides in one and the same cell, the nature (elementary granules or soluble product) of the material, and its site of release are discussed.     

The occurrence of biomineralization products in four lichen species growing on sandstone in western Norway

High performance thin-layer chromatography/thin-layer chromatography, X-ray diffraction, and scanning electron microscopy analysis of thallus and lichen-rock interface samples, were undertaken to characterize biomineralization products in Fuscidea cyathoides, Ochrolechia tartarea, Ophioparma ventosa, and Pertusaria corallina, growing on sandstone in western Norway. Whewellite (monohydrate form of Ca oxalate) was found in the thallus of all species, but not in any of the weathering rinds beneath the species. A significantly higher amount of whewellite was detected in the thalli of F. cyathoides and O. ventosa than in the other two species. There were only a few differences in whewellite occurrence between the thallus edge and centre samples in the four species. HPTLC/TLC and SEM analysis indicate that lichen compounds occur within the rock beneath some of the lichen specimens. Only divaricatic acid was observed within the weathering rind beneath O. ventosa. No lichen substances were found in the weathering rind beneath F. cyathoides and P. corallina, whereas gyrophoric and lecanoric acids were found in the weathering rind beneath O. tartarea.     

Growth of foliose lichens: a review

This review considers various aspects of the growth of foliose lichens including early growth and development, variation in radial growth rate (RaGR) of different species, growth to maturity, lobe growth variation, senescence and fragmentation, growth models, the influence of environmental variables, and the maintenance of thallus symmetry. The data suggest that a foliose lichen thallus is essentially a ‘colony’ in which the individual lobes exhibit a considerable degree of autonomy in their growth processes. During development, recognisable juvenile thalli are usually formed by 15 months to 4 years while most mature thalli exhibit RaGR between 1 and 5 mm yr⁻¹. RaGR within a species is highly variable. The growth rate-size curve of a foliose lichen thallus may result from growth processes that take place at the tips of individual lobes together with size-related changes in the intensity of competition for space between the marginal lobes. Radial growth and growth in mass is influenced by climatic and microclimatic factors and also by substratum factors such as rock and bark texture, chemistry, and nutrient enrichment. Possible future research topics include: (1) measuring fast growing foliose species through life, (2) the three dimensional changes that occur during lobe growth, (3) the cellular changes that occur during regeneration, growth, and division of lobes, and (4) the distribution and allocation of the major lichen carbohydrates within lobes.     

Distribution and abundance of littoral benthic fauna in Canadian prairie saline lakes

The littoral benthos of 18 lakes in Alberta and Saskatchewan ranging in salinity from 3 to 126 (g1^–1 TDS) were investigated twice, in the spring and in the summer of 1986. Multiple Ekman dredge samples were taken at water depths of about 0.5, 1.0 and 2 metres in each transect. Two to three transects were used in each lake according to its estimated limnological diversity for a total of 114 stations. A total of 76 species was present varying from 29–31 species in the three lakes of lowest salinity (means of 3.1–5.55) to only 2 species in lakes exceeding 100. Species richness decreased rapidly in salinities greater than 15.Biomass maximum mean of 10.91 g m^–2 dry weight (maximum 63.0 g m^–2) occurred in culturally eutrophic Humboldt Lake (3.1) but one third as great in other low salinity lakes. However, biomass again increased to about 4.5 gm^–2 in two lakes of 15 As the salinity increased still further biomass declined steadily until a minimum of 0.0212 g m^–2 was recorded in most saline Aroma Lake (mean 119). Summer biomass (11 lakes) was greater than spring biomass (4 lakes) because some groups such as amphipods, corixids and ostracods became more abundant in summer. Wet weight biomass averaged 15.8 of dry weight biomass.Seasonality (spring or summer), sediment texture and organic matter content, water depth, pH, salinity (TDS) and the presence of aquatic plants ( plant cover) were considered in the matrix involving species dry weight biomass at each of 117 stations. TWINSPAN classification of the samples yielded a dendrogram with 18 indicator species. Successive dichotomies divided these indicator species into four main lake groups based on salinity, i.e., Group I: 3–10 (Gammarus, Glyptotendipes I, Chironomus cf. plumosus), Group II: 10–38%. (Hyalella, Enallagma,Bezzia), Group III: 38–63 (Hygrotus salinarius, Cricotopus ornatus), Group IV: >63 (Dolichopodidae, Ephydra hians). Each of these main groups was subdivided into smaller groups of lakes based on factors such as pH, seasonality (spring or summer species dominance), organic matter and plant cover. Depth of samples played no apparent role.