Feeding group responses of a Neotropical termite assemblage to rain forest fragmentation

Biomass collapse and its associated microclimatic stresses within recently isolated rain forest fragments may negatively affect species diversity of most resident taxa. However, for some decomposer organisms, increased resource availability via accompanying tree die-off may effect positive responses, at least for a time, with implications for rates of nutrient cycling and greenhouse gas release. This study investigates the early effects of forest fragmentation on a Neotropical termite assemblage. Numbers of encounters (surrogate for relative abundance) and species richness of wood and leaf-litter feeders, soil feeders, and the whole assemblage, were studied across true forest islands and mainland sites at a hydroelectric reservoir in French Guiana. Results showed no overall effect of fragmentation on either total termite encounters or species richness. However, numbers of encounters and species richness of wood and leaf-litter feeders showed positive responses to forest fragmentation. By contrast, soil feeders showed a negative response for numbers of encounters and no significant effect for species richness. Environmental data suggest that increased tree die-off, and other edge effects associated with biomass collapse, were underway at the time of sampling. Resulting increase in resource availability may therefore explain the positive influence on wood and leaf-litter feeders. A possible decrease in predation pressure from ants with decrease in island size was not tested for, but was a likely effect of the flooded matrix habitat. Fragmentation effects on soil feeder encounters may be due to the energetic and microclimatic constraints of feeding lower down the humification gradient of termite food substrates, but were not sufficient to affect species richness. The patterns revealed suggest that rates of wood decomposition following tree die-off, and of soil nutrient cycling, under different rain forest fragmentation scenarios, merit further study.     

Juvenile hormone activity from various sources of termite castes and their fungus gardens

Summary Juvenile hormone (JH) activity is shown by extracts of the rectal contents of workers and soldiers, and anal exudate of queen of the termites,Microtermes sp.,Microcerotermes beesoni (Snyder),Odontotermes obesus (Rambur),O. qurdaspurensis (Holmgren) andO. assmuthi (Holmgren) as well as the fungus,Termitomyces sp. which is present in the termitaria. The possible significance of JH from various sources of termite castes and their fungus gardens is discussed.

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Zusammenfassung Es wurde festgestellt, dass bei den TermitenMicrotermes sp.,Microcerotermes beesoni (Snyder),Odontotermes obesus (Rambur),O. qurdaspurensis (Holmgren) andO. asmuthi (Holmgren). Extrakte aus dem Analexkret der Könign und aus dem Pilz des Termitenhaus (Termitomyces sp.) eine Juvenilhormonaktivität (JH) zeigen. Die wahrscheinliche Bedeutung dieserer Juvenilhormonaktivität aus verchredenen Termitenkasten und ihrer Pilzkultures wird diskutiert.

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Résumé L'activité de l'hormone juvénile (JH) est mise en évidence à partir d'extraits de contenu rectal d'ouvriers et de soldats et d'exsudat anal de reines de termites,Microtermes sp.,Microcerotermes beesoni (Snyder),Odontotermes obesus (Rambur),O. qurdaspurensis (Holmgren) etO. assmuthi (Holmgren), ainsi que du champignonTermitomyces sp. qui est présent dans la termitière. La signification possible de JH provenant de différentes sources, castes de termites ou champignons, est discutée.

     

Density of organic carbon in soil at coniferous forest sites in southern Finland

More detailed knowledge of the density of organic carbon in soils of boreal forests is needed for accurate estimates of the size of this C stock. We investigated the effect of vegetation type and associated site fertility on the C density at 30 mature coniferous forest sites in southern Finland and evaluated the importance of deep layers to the total C store in the soil by extending the sampling at eight of the sites to the depth of ground water level (2.4–4.6 m). The C density in the organic horizon plus 1 m thick mineral soil layer ranged from 4.0 kg/m² to 11.9 kg/m², and, on the average, increased towards the more productive vegetation types. Between the depth of 1 m and the ground water level the C density averaged 1.3–2.4 kg/m² at the studied vegetation types and these layers represented 18–28% of the total stock of C in the soil. The results emphasize the importance of also considering these deep layers to correctly estimate the total amount of C in these soils. At the least fertile sites the soil contained about 30% more C than phytomass, whereas at the more fertile sites the amount of C in soil was about 10% less than the amount bound in vegetation.     

Historical review and surveillance of Japanese encephalitis, Republic of Korea, 2002–2004

Japanese encephalitis virus (JEV), transmitted by culicine mosquitoes, is endemic throughout much of South‐East Asia, extending to the Korean Peninsula. The zoonotic cycle is from large water birds to culicine mosquitoes, with swine as an amplifying host and man as an incidental host. Culex tritaeniorhynchus, the primary JEV vector in the Republic of Korea, populations peak in late August through to early September when most cases of Japanese encephalitis (JE) are reported. Cx. tritaeniorhynchus were observed near the Demilitarized Zone in each of the years that mosquitoes were assayed for JEV. Each year that vector mosquitoes were assayed for JEV, minimum field infection rates (number of JEV positive mosquites/1000 Cx. tritaeniorhynchus assayed) ranged from 0.31 to 3.27. The epidemiology of JE has been recorded in Korea for more than half a century, from 1949 to 2005. During a major epidemic in 1949, there were 5616 cases and 2729 deaths reported, with levels persisting near epidemic levels of 1000 cases annually thereafter until 1969. Following the introduction and government mandated mass immunization in 1971, JE decreased dramatically. Since 1984, 0–6 cases of JE have been reported each year. However, continued evidence of mosquitoes positive for JEV indicates that JE continues to be a civilian and military health threat to immunocompromised persons in Korea, as well as non‐immune US soldiers, civilians and their family members.     

Isolation of fecal coliforms from pristine sites in a tropical rain forest

Samples collected from water accumulated in leaf axilae of bromeliads (epiphytic flora) in a tropical rain forest were found to harbor fecal coliforms. Random identification of fecal coliform-positive isolates demonstrated the presence of Escherichia coli. This bacterium was also isolated from bromeliad leaf surfaces. These data indicate that E. coli may be part of the phyllosphere microflora and not simply a transient bacterium of this habitat. The isolation of fecal coliforms from these sites was unexpected and raises questions as to the validity of using fecal coliforms as indicators of biological water quality in the tropics.     

A test of seasonal responses to sugars in four populations of the termite Reticulitermes flavipes

Several studies have shown that Reticulitermes termites prefer food with certain types of sugars. However, the specific sugars that were preferred by the termites in each study differed. The difference between the results of these studies might be explained by differences between populations or changes in feeding responses during the active season. To address these variables, we examined the feeding response to a food source food containing glucose, sucrose, or xylose versus a food source without sugar in several populations of termites and observed whether these responses changed during the year. Termites were collected from colonies from four field sites in Missouri during the spring (May and June), summer (July and August), and fall (September and October) and tested for their response to all three sugars under laboratory conditions. Results show there are distinct differences in response to sugars between populations but only a slight seasonal effect.     

Alkaline phosphatase activity at unusual sites of human foetal kidney

Summary Frozen sections of human foetal kidneys were treated by the lead citrate method in order to demonstrate alkaline phosphatase (ALP) activity. Unexpectedly, ALP activity was observed over the parietal layer of Bowman's capsule, in addition to usual localization in proximal tubules and blood vessels. The enzyme was confined to the membrane of microvilli belonging to tall columnar cells. Normally, in the mature nephron, these high cells are absent from the parietal layer that is instead entirely composed of squamous epithelium.ALP activity was also revealed at another unusual site in the kidney medulla. A collar of mesenchymal cells encapsulating groups of tubules and calyces gave an intense enzymatic reaction. The activity was present over the membrane of long cytoplasmic processes. The cytoplasm showed a well developed rough endoplasmic reticulum, an indication of a high rate of protein synthesis. The nearby presence of numerous collagenous fibrils is concordant with this assumption. Moreover, these ALP-positive cells might represent an intermediary stage through which cells have to pass before differentiating.     

Rates of litterfall and organic matter turnover at three South Australian indigenous forest sites

A quantitative study of the litterfall rate, litter mass and the organic carbon content of litter and soil at three South Australian low open-forests was made monthly for 2 years. The soil and dominant vegetation at the sites were similar, but the mean annual rainfall differed; 635, 690 and 1050 mm respectively at the ‘dry’, ‘medium’ and ‘wet’ sites. Mean annual litterfall at the dry, medium and wet sites was 114, 205 and 233 g m^?2 respectively, and the mean mass of the litter layer was 885, 1153 and 858 g m^?2 Leafy material formed 82% of the litterfall at each site and maximum fall occurred in the summer. Leafy material formed 64–68% of the three litter layers and there was no general pattern of seasonal change of mass. The data obtained were used to calculate the half-life (T_1/2 of the litter, the values were 5.4, 3.9 and 2.6 years respectively at the dry, medium and wet sites. The values from the medium and wet sites fit within the range previously recorded for other open-forests and low open-forests, but indicate an extremely slow rate of decomposition at the dry site, which was located close to open-scrubland. The amounts of organic carbon in the 0–8 cm layer of soil at the dry, medium and wet sites were 777, 928and 950 g m^-2 respectively. However, without a detailed investigation of the source of soil carbon, these values could only be used to show that the organic carbon store to a depth of 8 cm is equivalent to 9–15 times the annual litterfall input.     

从白蚁中分离到具有纤维素酶活的贪噬菌

以黄胸散白蚁Reticulitermes flaviceps后肠为材料,分离培养具有降解纤维素能力的微生物,以进一步了解白蚁后肠微生物的种类。通过以羧甲基纤维素钠(CMC-Na)为唯一碳源的富集及选择培养基培养、筛选,获得一株具有纤维素酶活的菌株R3063。形态学鉴定、革兰氏染色观察及16S rDNA基因序列分析表明该菌株属于贪噬菌(Variovorax sp.)。目前尚未见贪噬菌具有纤维素酶活的报道。     

Isolation of fecal coliforms from pristine sites in a tropical rain forest.

Samples collected from water accumulated in leaf axilae of bromeliads (epiphytic flora) in a tropical rain forest were found to harbor fecal coliforms. Random identification of fecal coliform-positive isolates demonstrated the presence of Escherichia coli. This bacterium was also isolated from bromeliad leaf surfaces. These data indicate that E. coli may be part of the phyllosphere microflora and not simply a transient bacterium of this habitat. The isolation of fecal coliforms from these sites was unexpected and raises questions as to the validity of using fecal coliforms as indicators of biological water quality in the tropics.     

Leaf-nutrient accumulation and turnover at three stages of succession from heathland to forest

Abstract. Accumulation of nutrients in leaves of the dominating species of three ecosystems, characterizing the secondary succession from Genisto-Callunetum heathland through Leucobryo-Pinetum birch-pine woodland to mature Querco-Fagetum oak-beech forest, as well as nutrient turnover within these ecosystems was studied. The objective of the study was to establish potential variations in quantity and quality of nutrient supply to the plants with respect to succession dynamics. The results show very low leaf nutrient concentrations of all species investigated, coinciding with low nutrient availability in the soil. However, the nutrient content of leaves and leaf litter of Quercus petraea and Fagus sylvatica, which dominate the late succession stages, and in Betulapéndula are higher than in the photosynthetic organs (leaves and young shoots) of Calluna vulgaris and Pinus sylvestris. The combination of the higher nutrient content of the leaves and an increasing leaf-litter production during succession results in an increased nutrient turnover via leaf-litter fall. However, due to the high leaf biomass, the storage of nutrients in the leaf biomass is highest within the birch-pine woodland. From this, it may be assumed that the low demand and the low loss of nutrients via leaf-litter fall are favourable for Pinus at the early stages of forest succession on poor sandy soils. In contrast, Quercus and Fagus are provided with better growth conditions at the later stages of succession resulting from the accumulation of plant-available nutrients in the ecosystem by Pinus sylvestris, combined with a higher nutrient turnover as compared with the heathland.     

Changes in termite (Isoptera) communities due to the clearance and cultivation of tropical forest in Uganda

Changes in termite communities following clearance and cultivation of part of Mabira Forest Reserve were studied. The study sites included natural forest, a cleared but not cultivated site and six sites cultivated for different periods, ranging from 1 to 20 years.
A total of 25 species, including Odontotermes amanicus (Sjostedt) and Microtermes luteus (Harris), both not previously identified in Uganda, was recorded in the natural forest. Forest clearance resulted in drastic reduction of the number of species to about 40% of what existed in the natural forest, while cultivation led to further elimination, leaving only four and two species, respectively, in the 1- and 20-year-old banana groves.
The study showed that termite species diversity declines when the natural forest is cleared and cultivated. It is suggested that reduction in termite diversity alters ecological processes and may result in diminishing productivity with time.     

Collagenolytic activity of rabbit V2-carcinoma growing at multiple sites.

Interaction between lanosterol and cytochrome P-450 purified from microsomes of anaerobically-grown Saccharomyces cerevisiae was studied. Lanosterol (4,4,14α-trimethyl-5α-cholesta-8,24-dien-3β-ol) stimulated the oxidation of NADPH by molecular oxygen in the presence of cytochrome P-450 and NADPH-cytochrome P-450 reductase both purified from S. cerevisiae microsomes. Lanosterol stimulated the reduction of cytochrome P-450 by NADPH with the cytochrome P-450 reductase, and induced Type I spectral change of cytochrome P-450. These observations suggest that lanosterol interacts to the substrate region of cytochrome P-450 of S. cerevisiae. Based on these facts, possible role of cytochrome P-450 in lanosterol metabolism in yeast cell is discussed.     

Some observations on the location of sites of fungal activity at Blelham Tarn

Summary Using a previously described method to enumerate viable propagules of Saprolegniales, an attempt has been made to locate major sites of activity of this group of fungi at Blelham Tarn (English Lake District). There was evidence of high activity in periodically inundated soils at the lake margin, but not in bottom muds from the lake itself.

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Zusammenfassung Mittels einer früher beschriebenen Methode die vermehrungsfähigen Teile der Saprolegniales festzustellen, wurden die wichtigsten Zonen ihrer Wirkungskreise bei Blelham Tarn (Englisches Seegebiet) gefunden. Es wurde gezeigt, dass sie am meisten im Boden am Seerand, welcher öfters überschwemmt ist, vorkommen, aber nicht im Schlamm des Sees selbst.

     

Phloxine B interacts with the cystic fibrosis transmembrane conductance regulator at multiple sites to modulate channel activity

The fluorescein derivative phloxine B is a potent modulator of the cystic fibrosis transmembrane conductance regulator (CFTR). Low micromolar concentrations of phloxine B stimulate CFTR Cl(-) currents, whereas higher concentrations of the drug inhibit CFTR. In this study, we investigated the mechanism of action of phloxine B. Phloxine B (1 microm) stimulated wild-type CFTR and the most common cystic fibrosis mutation, DeltaF508, by increasing the open probability of phosphorylated CFTR Cl(-) channels. At each concentration of ATP tested, the drug slowed the rate of channel closure without altering the opening rate. Based on the effects of fluorescein derivatives on transport ATPases, these data suggest that phloxine B might stimulate CFTR by binding to the ATP-binding site of the second nucleotide-binding domain (NBD2) to slow the dissociation of ATP from NBD1. Channel block by phloxine B (40 microm) was voltage-dependent, enhanced when external Cl(-) concentration was reduced and unaffected by ATP (5 mm), suggesting that phloxine B inhibits CFTR by occluding the pore. We conclude that phloxine B interacts directly with CFTR at multiple sites to modulate channel activity. It or related agents might be of value in the development of new treatments for diseases caused by the malfunction of CFTR.