Feeny revisited: condensed tannins as anti-herbivore defences in leaf-chewing herbivore communities of Quercus

Abstract. 1. Community level oak–tannin–insect patterns have been largely unexplored since Paul Feeny's ground‐breaking research. Two hypotheses were tested for Quercus velutina and Q. alba in the Missouri Ozarks: abundance and richness of leaf‐chewing herbivores are negatively correlated with foliar condensed tannin concentrations and variation in condensed tannin concentrations explains variation in herbivore community structure. 2. In 2001, foliar condensed tannins in the understorey and canopy of these two oak species were quantified simultaneously with censuses of herbivores in May, during leaf expansion, and in June and August, when leaves were fully expanded. Thirty‐eight of the 134 species encountered had densities sufficient to be analysed individually (n = 10). Of those, Acronicta increta (Noctuidae) and Attelabus sp. (Curculionidae), both oak specialists, were negatively correlated with condensed tannins in the canopy of Q. alba. One additional specialist, Chionodes pereyra (Gelechiidae), was marginally negatively correlated with condensed tannins in the understorey of Q. velutina. Understorey species richness of May Q. velutina herbivores was negatively correlated with condensed tannins, as were total canopy insect density and species richness of August herbivores on Q. alba. 3. Principal component analysis (PCA) of insect abundances indicated that understorey and canopy Q. velutina and Q. alba had different communities of leaf‐chewing insects. Furthermore, condensed tannin levels contributed significantly to variation in PCA scores for Q. velutina, explaining 25% of the total variation. 4. Overall, these results indicate that specialists were more likely than generalists both to correlate negatively with condensed tannins and to occur in lower tannin habitats; abundance and richness of both early and late season fauna correlated negatively with tannins; and species were more likely to correlate negatively with condensed tannins when feeding on Q. alba than on Q. velutina and when feeding in the canopy than in the understorey. Future studies of tannin–insect interactions should manipulate leaf quality in combination with manipulations of other factors that likely influence community structure.     

根田鼠对食物单宁酸的解毒代价

在实验室条件下,测定了根田鼠对单宁酸的解毒代价。结果表明,在食物蛋白质为10％的条件下,摄食3％和6％单宁酸食物的根田鼠经尿液分泌的葡萄糖醛酸较对照组分别增加13．77％和38．80％;与对照组比较,在食物蛋白质为20％的条件下,摄食3％和6％单宁酸食物的实验个体尿液分泌的葡萄糖醛酸分别增加6．11％和22．25％。在食物蛋白质为10％时,用3％和6％单宁酸食物处理的个体,其尿液NH4^ —N含量较对照组个体分别增加51．69％和198．44％。在食物中蛋白质为20％时,摄食3％和6％单宁酸食物的试验个体,其尿液中的NH4^ —N含量分别较对照组高1．72％和74．19％。由此说明,单宁酸能显著增加根田鼠尿液葡萄糖醛酸分泌量,根田鼠尿液的NH4^ —N的含量随食物单宁酸增加而增高,从而增加动物机体对单宁酸的代谢价。     

Increasing the oxidative stress response allows Escherichia coli to overcome inhibitory effects of condensed tannins

Tannins are plant-derived polyphenols with antimicrobial effects. The mechanism of tannin toxicity towards Escherichia coli was determined by using an extract from Acacia mearnsii (Black wattle) as a source of condensed tannins (proanthocyanidins). E. coli growth was inhibited by tannins only when tannins were exposed to oxygen. Tannins auto-oxidize, and substantial hydrogen peroxide was generated when they were added to aerobic media. The addition of exogenous catalase permitted growth in tannin medium. E. coli mutants that lacked HPI, the major catalase, were especially sensitive to tannins, while oxyR mutants that constitutively overexpress antioxidant enzymes were resistant. A tannin-resistant mutant was isolated in which a promoter-region point mutation increased the level of HPI by 10-fold. Our results indicate that wattle condensed tannins are toxic to E. coli in aerobic medium primarily because they generate H(2)O(2). The oxidative stress response helps E. coli strains to overcome their inhibitory effect.     

Tannin inclusions in cell suspension cultures of white spruce

Summary Tannins were detected cytochemically in cell suspension cultures of white spruce (Picea glauca [Moench] Voss) and were studied by electron microscopy. Tannin inclusions originated within cytoplasmic vacuoles, possibly derived from the endoplasmic reticulum, and accumulated in the central vacuole through enlargement and coalescence of those cytoplasmic vacuoles. Structural information supported the suggested metabolic relationship between starch and tannin, although tannins did not develop within plastids. Membranous material, resembling myelinlike bodies, was often observed in close association with tannins.     

Effects of simulated winter browsing on mountain birch foliar chemistry and on the performance of insect herbivores

Winter browsing by mammalian herbivores is known to induce a variety of morphological and physiological changes in plants. Browsing has been suggested to decrease the carbohydrate reserves in woody plants, which might lead to reduced tannin production in leaves during the following summer, and consequently, to increased herbivore damage on leaves. We conducted a clipping experiment with mature mountain birch trees and measured the effects of clipping on birch growth, leaf chemistry and toughness, as well as on the performance of insect herbivores. Leaves grew larger and heavier per unit area in the clipped ramets and had a higher content of proteins than leaves in the control trees. Clipping treatment did not affect the total content of sugars in the leaves (mg g^?1), suggesting that a moderate level of clipping did not significantly reduce the carbohydrate pools of fully‐grown mountain birch trees. Furthermore, the contents of proanthocyanidins (condensed tannins) and gallotannins were slightly higher in the leaves of clipped ramets, contrary to the hypothesis of reduced tannin production. The effects of clipping treatment on leaf and shoot growth and on foliar chemistry were mainly restricted to the clipped ramets, without spreading to untreated ramets within the same tree individual. The effects of clipping on leaf characters varied during the growing season; for instance, leaf toughness in clipped ramets was higher than toughness in control trees and ramets only when leaves were mature. Accordingly, clipping had inconsistent effects on insect herbivores feeding at different times of the growing season. The generally small impact of clipping on herbivore performance suggests that the low intensity of natural browsing at the study area, simulated by our clipping treatment, does not have strong consequences for the population dynamics of insect herbivores on mountain birch via enhanced population growth caused by browsing‐induced changes in food quality.     

Defence,growth and nutrient allocation in the tropical shrub Bauhinia brevipes (Leguminosae)

Herbivory in natural communities can be high, reducing the growth and reproduction of individual plants. To diminish the impact of herbivores, plants use a variety of defensive mechanisms. It is now recognized that the plant world is characterized by a proliferation of secondary metabolites, but models of the evolution of defence strategies assume that plants are constrained by finite resources, and that defences are costly. In the present study, the relationships between defence, growth and nutrient concentration in Bauhinia brevipes Vog. (Leguminosae) in south‐eastern Brazil were investigated. Patterns of herbivory and defence were examined for 170 B. brevipes individuals in 1997 and 1998. Leaf age influenced tannin concentration and herbivore attack on B. brevipes. Mature leaves had higher concentrations of tannins than young leaves, and young leaves were approximately 60% more likely to be attacked than mature leaves. Carbon and nitrogen content explained 36% of the variation in the percentage of attacked leaves in B. brevipes (y = 16.29 – 0.31 C + 0.25 N; r² = 0.36; F = 9.56; P < 0.0001). Tannins acted as defensive compounds on B. brevipes leaves against free‐feeding herbivores, but no clear pattern was observed against galling herbivores. The amounts of nitrogen, carbon, potassium, and aluminium explained approximately 69% of the variation in tannin concentration on B. brevipes leaves (y = 0.62 – 0.16 N – 0.36 K – 0.26 Al + 0.74 C; r² = 0.69; F = 21.18; P < 0.0001). We found an inverse relationship between shoot growth rates and tannin concentration in B. brevipes, indicating that the production of tannins may be costly, therefore offering some evidence for the trade‐off hypothesis. Nevertheless, the weak relationship observed between herbivore damage and tannin concentration indicates that other factors are also involved with herbivore pressure.     

Seasonal and interspecific variation in the biochemical composition of some British fern species and their effects on Spodoptera littoralis larvae

Fern-feeding insects in Britain are mainly found on mature fronds in late summer. Six fern species (Dtyopteris filix-mas, D. dilatata, D. borreri, Phyllitis scolopendrium, Polyslkhum setiferum and Polypodium vulgare) were analysed for fibre, lignin, cellulose, tannins, cyanogenesis and thiaminase activity in an attempt to determine the biochemical basis for this seasonal pattern of attack. A bioassay was also carried out, using frond material incorporated in the diet of Spodoptera littoralis, to determine the effects of seasonal changes in fern toxins on a non-adapted, insect herbivore. The young fronds of all six species had a high protein content and low fibre-lignocellulose; protein levels decreased and cell wall materials increased as the fronds matured. Tannin concentrations and thiaminase activity showed a less consistent seasonal pattern. Tannins were present in the highest concentration in the young fronds of D. borreri, Polystichum and Polypodium and decreased with season; D. dilatata, Polystichum and Polypodium showed a similar pattern of thiaminase activity. The other species showed no strong seasonality in the levels of either tannins or thiaminase. No cyanogenic activity was detected in any of the fern species. Frond material from all six species decreased survivorship and growth rates of Spodoptera larvae. Larval performance and growth on diets containing fern material from young immature fronds was generally poorer than on diets containing material from mature fronds, collected later in the season. Neither tannin concentrations nor thiaminase activity levels closely corresponded to the observed interspecific and seasonal patterns of larval development and mortality, and other toxins must be involved. It is concluded that ferns are highly toxic to non-adapted herbivorous insects but the effects on adapted species are unknown. The restricted seasonal occurrence of a small number of insect species exhibiting specialized feeding habits suggests, however, that biochemical properties of the ferns determine this pattern of attack and limit the number of species which are able to exploit ferns as food resources.     

Antimicrobial properties of tannins

Tannin toxicity for fungi, bacteria and yeasts is reviewed and compared to toxicity of related lower molecular weight phenols. The dependence of toxicity on tannin structure is examined. The different mechanisms proposed so far to explain tannin antimicrobial activity include inhibition of extracellular microbial enzymes, deprivation of the substrates required for microbial growth or direct action on microbial metabolism through inhibition of oxidative phosphorylation. A further mechanism involving iron deprivation is proposed. Many microorganisms can overcome plant defences based on tannins. They may detoxify tannins through synthesis of tannin- complexing polymers, oxidation, tannin biodegradation or synthesis of siderophores.     

Tree resistance to Lymantria dispar caterpillars: importance and limitations of foliar tannin composition

The ability of foliar tannins to increase plant resistance to herbivores is potentially determined by the composition of the tannins; hydrolyzable tannins are much more active as prooxidants in the guts of caterpillars than are condensed tannins. By manipulating the tannin compositions of two contrasting tree species, this work examined: (1) whether increased levels of hydrolyzable tannins increase the resistance of red oak (Quercus rubra L.), a tree with low resistance that produces mainly condensed tannins, and (2) whether increased levels of condensed tannins decrease the resistance of sugar maple (Acer saccharum Marsh.), a tree with relatively high resistance that produces high levels of hydrolyzable tannins. As expected, when Lymantria dispar L. caterpillars ingested oak leaves coated with hydrolyzable tannins, levels of hydrolyzable tannin oxidation increased in their midgut contents. However, increased tannin oxidation had no significant impact on oxidative stress in the surrounding midgut tissues. Although growth efficiencies were decreased by hydrolyzable tannins, growth rates remained unchanged, suggesting that additional hydrolyzable tannins are not sufficient to increase the resistance of oak. In larvae on condensed tannin-coated maple, no antioxidant effects were observed in the midgut, and levels of tannin oxidation remained high. Consequently, neither oxidative stress in midgut tissues nor larval performance were significantly affected by high levels of condensed tannins. Post hoc comparisons of physiological mechanisms related to tree resistance revealed that maple produced not only higher levels of oxidative stress in the midgut lumen and midgut tissues of L. dispar, but also decreased protein utilization efficiency compared with oak. Our results suggest that high levels of hydrolyzable tannins are important for producing oxidative stress, but increased tree resistance to caterpillars may require additional factors, such as those that produce nutritional stress.     

Effects of tree age and stand thinning related variations in balsam fir secondary compounds on spruce budworm Choristoneura fumiferana development,growth and food utilization

• 1 The effect of tannins and monoterpenes on the development, mortality and food utilization of spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae) was investigated under laboratory conditions using an artificial diet. Tannins were extracted from balsam fir foliage of thinned and unthinned stands to reproduce stand thinning related variations in tannins. A mixture of synthetic monoterpenes was utilized to simulate the concentration found in young and old balsam fir trees.
• 2 Longer development time and lower pupal weight were observed for insects fed on diets with a lower nitrogen concentration and a higher tannin concentration (unthinned treatment). Tannins induced higher insect mortality at a low nitrogen concentration compared with the diet with a higher nitrogen concentration.
• 3 Approximate digestibility was higher for larvae fed on diets with high concentrations of nitrogen at both low and high concentrations of tannins. Efficiency of conversion of digested food (ECD) decreased with an increase in tannin concentration. Tannins reduced both the relative consumption and growth rate (RCR and RGR).
• 4 Monoterpenes increased spruce budworm mortality and this mortality reached almost 50% under concentrations of monoterpene typical of the young trees compared with 20% under monoterpene concentrations found in old trees.
• 5 A higher digestibility was observed for larvae fed on diet with a higher concentration of monoterpenes, whereas efficiency of conversion of ingested food (ECI), ECD, RCR, and RGR decreased with an increase in monoterpenes in the diet.
• 6 The results obtained in the present study are consistent with the defensive role of secondary compounds such as tannins and monoterpenes in the spruce budworm–balsam fir system.

     

Natural tannins as anti-SARS-CoV-2 compounds

Tannins are polyphenols enriched in wood, bark, roots, leaves, seeds and fruits of a variety of plants. Over the last two decades, there has been an increasing interest in understanding the biological functions of tannins and their applications as antioxidants, anticancer drugs, and food additives. Since the outbreak of the COVID-19 pandemic, much effort has been devoted to finding an expedient cure. Tannins have been put forward as having possible anti-COVID-19 properties; however, owing to the profuse nature of the structurally diverse derivatives of tannins, the tannin species in the family associated with an indication of anti-COVID-19 have been poorly defined, compounded by frequent terminology misnomers. This article reviews the tannin family in fruits and the current knowledge about the activities of the compounds with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It will aid molecular and cellular biologists in developing natural anti-viral chemicals as means of overcoming the current and future pandemics.     

Effects of genetic variability and habitat of Qualea parviflora (Vochysiaceae) on herbivory by free-feeding and gall-forming insects

• Background and Aims Differences in the chemical and physical traits of plants caused by both genetic and habitat characteristics may influence attack by herbivores. Leaves of Qualea parviflora (Vochysiaceae), a common tree of different habitats in the Brazilian Neotropical savannas (cerrado), are susceptible to severe attack by herbivorous free-living and gall-forming insects. Attack by free-living and gall-forming insects within and between populations of Q. parviflora were examined and it was determined to what extent genetic variability (detected by RAPD markers), phenotypic characteristics of the plants and habit traits influence the number of free-living and gall-forming insect species and individuals attacking the plants, and the intensity of attack.• Methods On four occasions in 2000, leaves were sampled from ten individual trees in each of three types of vegetation in the cerrado: campo sujo, cerrado sensu stricto and cerradão at the Ecological Station of Pirapitinga (ESP), in Três Marias, north-western Minas Gerais, Brazil. Genetic variability was detected by RAPD markers, and concentrations of nutrients, phenols and tannins, sclerophylly and pre-dawn water potential of leaves were measured. Water and nutrient contents in the soil below each tree characterized the habitat. The free-living and gall-forming herbivorous insects were determined.• Key Results Of 69 RAPD markers analysed, 41 were polymorphic and were used for analyses of genetic variability of Q. parviflora. Most of the variability occurred within habitats, accounting for 97·65 % of the genetic variability. Plants in the cerrado sensu stricto and campo sujo were the most similar. There were no significant associations between genetic similarity and the chemical and physical traits of Q. parviflora, or with habitat, nor was there significant correlation between phenotypic and habitat traits. Increasing concentrations of tannins and sulphur, C : N ratio and sclerophylly correlated with increasing percentage of leaf area damaged by herbivores. Decreased sclerophylly, concentration of tannins and C : N ratio, and increased concentration of nutrients in leaves correlated with increased severity of attack by gall-forming insects.• Conclusions Nutrient concentration in the soil had more influence, indirectly, on free-feeding insects than did composition of Q. parviflora leaves. However, gall-forming insects are affected more by leaf quality, attacking fewer sclerophyllous leaves, with larger nutrient but smaller tannin concentrations.Key words: Cerrado, genetic variability, gall attack, herbivory, insect galls, plant quality, Qualea parviflora, RAPD, Vochysiaceae     

Tannins in nutrient dynamics of forest ecosystems - a review

Tannins make up a significant portion of forest carbon pools and foliage and bark may contain up to 40% tannin. Like many other plant secondary compounds, tannins were believed to function primarily as herbivore deterrents. However, recent evidence casts doubts on their universal effectiveness against herbivory. Alternatively, tannins may play an important role in plant–plant and plant–litter–soil interactions. The convergent evolution of tannin-rich plant communities on highly acidic and infertile soils throughout the world, and the intraspecific variation in tannin concentrations along edaphic gradients suggests that tannins can affect nutrient cycles. This paper reviews nutrient dynamics in forest ecosystems in relation to tannins. Tannins comprise a complex class of organic compounds whose concentration and chemistry differ greatly both among and within plant species. Because the function and reactivity of tannins are strongly controlled by their chemical structure, the effects of tannins on forest ecosystem processes are expected to vary widely. Tannins can affect nutrient cycling by hindering decomposition rates, complexing proteins, inducing toxicity to microbial populations and inhibiting enzyme activities. As a result, tannins may reduce nutrient losses in infertile ecosystems and may alter N cycling to enhance the level of organic versus mineral N forms. The ecological consequences of elevated tannin levels may include allelopathic responses, changes in soil quality and reduced ecosystem productivity. These effects may alter or control successional pathways. While a great deal of research has addressed tannins and their role in nutrient dynamics, there are many facets of tannin biogeochemistry that are not known. This lack of information hinders a complete synthesis of tannin effects on forest ecosystem processes and nutrient cycling. Areas of study that would help clarify the role of tannins in forest ecosystems include improved characterization and quantification techniques, enhanced understanding of structure-activity relationships, investigation of the fate of tannins in soil, further determination of the influence of environmental factors on plant tannin production and decomposition, and additional information on the effects of tannins on soil organisms.     

Increasing the Oxidative Stress Response Allows Escherichia coli To Overcome Inhibitory Effects of Condensed Tannins

Tannins are plant-derived polyphenols with antimicrobial effects. The mechanism of tannin toxicity towards Escherichia coli was determined by using an extract from Acacia mearnsii (Black wattle) as a source of condensed tannins (proanthocyanidins). E. coli growth was inhibited by tannins only when tannins were exposed to oxygen. Tannins auto-oxidize, and substantial hydrogen peroxide was generated when they were added to aerobic media. The addition of exogenous catalase permitted growth in tannin medium. E. coli mutants that lacked HPI, the major catalase, were especially sensitive to tannins, while oxyR mutants that constitutively overexpress antioxidant enzymes were resistant. A tannin-resistant mutant was isolated in which a promoter-region point mutation increased the level of HPI by 10-fold. Our results indicate that wattle condensed tannins are toxic to E. coli in aerobic medium primarily because they generate H₂O₂. The oxidative stress response helps E. coli strains to overcome their inhibitory effect.     

Costs and benefits of defense by tannins in a neotropical tree

Summary The costs and benefits of defense by tannins were investigated for a neotropical tree, Cecropia peltata L. (Moraceae). Seedlings of equal age were grown under uniform conditions in a greenhouse for 18 months. Within a plant, leaf tannin concentrations measured in different years were highly correlated. Tannin concentrations differed substantially among individuals; plants with high tannin content had lower damage levels in herbivory experiments. The effects of tannin on herbivory appeared to be dosage dependent. There was, however, a cost associated with tannin production in terms of reduced leaf production.     

山茱萸果实发育过程中单宁物质的分布与积累特征

选取不同发育时期的山茱萸果实作为研究对象,采用果实形态观察法、显微及超微技术、组织化学定位法以及紫外分光光度计法对山茱萸果实发育过程中单宁物质分布及积累特征进行观察分析,并以单因素ANOVA检验不同发育时期单宁含量的差异,以揭示单宁物质在山茱萸果实发育中的变化规律,为山茱萸果实涩味调控机制研究提供理论依据。结果表明:(1)山茱萸果实发育过程中果皮颜色和果实体积变化明显,可将其发育过程划分为幼果期、中果期、成熟期3个时期;单宁物质主要分布在山茱萸果实中果皮的单宁细胞中。(2)在山茱萸果实发育过程中单宁细胞数目呈先增后减的变化趋势,幼果期单宁细胞从无到有,随着果实发育单宁细胞数目不断增多,至中果期单宁细胞数目开始减少。(3)单宁含量的变化规律与单宁细胞数目的变化一致,单宁含量在花后120 d时达到最多,随后逐渐减少。(4)单宁物质首先在细胞质的小液泡中积累,中央大液泡形成后则为单宁物质积累的主要场所,其积累形态主要有颗粒状、不规则状和板块状3种;单宁细胞中线粒体数目较多,中果期后期及成熟期在中央大液泡液泡膜附近有电子致密物质积累。研究认为,山茱萸果实中中果皮薄壁细胞为单宁物质积累的专属细胞,即单宁细胞,单宁物质的合成运输与液泡、囊泡以及线粒体的作用密切相关;成熟期山茱萸果实总单宁含量降低,涩味降低,表明单宁物质积累的动态变化与植物对环境的适应性和果实涩味息息相关,可结合代谢组和转录组的方法对山茱萸果实中单宁物质的合成机制进行进一步研究。     

Relationships among Key deer, insect herbivores, and plant quality

Deer can have severe effects on plant communities, which in turn can affect insect communities. We studied the effects of Key deer herbivory on the incidence of insect herbivores that occur within deer habitats in the lower Florida Keys, within the National Key Deer Refuge (NKDR). We analyzed plant chemistry (tannins, nitrogen) and surveyed for the occurrence of insects (above the browse tier) among plant species that were either deer-preferred or less-preferred. Results indicated higher levels of foliar tannins on islands with fewer Key deer and larger amounts of foliar nitrogen on islands with a high density of Key deer. Consequently, leaf miners were significantly more abundant on islands with high deer density, irrespective of deer-preference of plant species. On islands with a high deer density, incidence of leaves damaged by chewing insects was lower on preferred plant species but greater on less-preferred species than on islands with fewer deer. No apparent patterns were evident in the distribution of leaf gallers among plant species or islands with different deer density. Our results imply that plant nutrition levels—either preexisting or indirectly affected by deer deposition—are more important than plant defenses in determining the distribution of insect herbivores in the NKDR. Although high densities of the endangered Key deer have negative effects on some plant species in the NKDR, it seems Key deer might have an indirect positive influence on insect incidence primarily above the browse tier. Further research is warranted to enable fuller understanding of the interactions between Key deer and the insect community.     

Leaf trait variation on Erythroxylum tortuosum (Erythroxylaceae) and its relationship with oviposition preference and stress by a host‐specific leaf miner

It has been suggested that plant physical and chemical traits vary considerably in space and time. Hence, leaf‐mining insects may adjust their oviposition in response to leaf attributes representing high quality. Moreover, herbivorous insects can modify leaf morphology by acting as stressors, increasing, for example, fluctuating asymmetry (FA) levels. Here, we investigate oviposition preference in Agnippe sp.2, a leaf‐mining moth of Erythroxylum tortuosum, in relation to differences in leaf nutritional quality (i.e. levels of water, nitrogen and tannin content), leaf area (i.e. quantity of resource hypothesis) and FA. We also verify whether temporal variation in plant nutritional quality emerges as an alternative hypothesis to explain oviposition distribution in time, and whether this leaf miner is a stress‐causing agent, increasing FA during larval development. Mined leaves and leaves with and without eggs were periodically collected from plants located in a Cerrado fragment in Brazil. In the laboratory, leaf traits were assessed (using image analysis software) and quantified (biochemical analysis) according to the aims previously determined. Oviposition probability did not change in relation to variations in nitrogen, tannins and FA of leaves. However, leaf‐miner females preferred to oviposit on leaves having large areas and low water contents. It was also verified that new leaves of E. tortuosum, which carried most leaf‐miner eggs, presented significantly lower tannins and greater levels of nitrogen and water than old leaves. The oviposition choice exhibited by leaf miners was found to be non‐random because they appear to use resource quantity and water content as cues as where to lay their eggs. The temporal variation of plant nutritional quality is likely to influence the time of leaf‐miner oviposition; and leaf FA was not increased during larval feeding, suggesting that these herbivores do not cause variations in FA levels.     

Biotransformation of industrial tannins by filamentous fungi

Tannins are secondary metabolites that are widely distributed in the plant kingdom. They act as growth inhibitors for many microorganisms: they are released upon microbial attack, helping to fight infection in plant tissues. Extraction of tannins from plants is an active industrial sector with several applications, including oenology, animal feeding, mining, the chemical industry, and, in particular, the tanning industry. However, tannins are also considered very recalcitrant pollutants in wastewater of diverse origin. The ability to grow on plant substrates rich in tannins and on industrial tannin preparations is usually considered typical of some species of fungi. These organisms are able to tolerate the toxicity of tannins thanks to the production of enzymes that transform or degrade these substrates, mainly through hydrolysis and oxidation. Filamentous fungi capable of degrading tannins could have a strong environmental impact as bioremediation agents, in particular in the treatment of tanning wastewaters.

     

Increase in tannin consumption by sifaka (<Emphasis Type="Italic">Propithecus verreauxi verreauxi</Emphasis>) females during the birth season: a case for self-medication in prosimians?

In this study we report preliminary data on the consumption of tannin-rich plants by sifakas (Propithecus verreauxi verreauxi) living in the Kirindy forest, western Madagascar. Sifakas spent most of their time feeding on only a few plant species. The tannin intake during the period between the pregnancy and birth season was significantly higher in pregnant females or females with lactating infants than in non-reproductive females and males. These periparturient females secured a larger proportion of condensed tannins by short feeding bouts on plants not included in the group's limited preferred food species. The measured increase in tannin intake is puzzling in light of the fact that tannins are commonly known for their protein-binding properties. Since protein demands are highest in pregnant and lactating females, possible medicinal benefits of tannin ingestion are considered. Tannin consumption is associated with an increase in body weight and stimulation of milk secretion. Veterinarians administer tannins as an astringent, anti-hemorrhagic and anti-abortive. Their high potential as an alternative anthelminthic has also recently been recognized. Thus, when viewed as self-medicating behavior, controlled increase in tannin intake could have multiple prophylactic advantages for females during the periparturient period. The high selectivity in their plant choice, and the presence of unusual feeding habits by a particular group of individuals (females with infants) limited in time (birth season), suggests that an increase in tannin ingestion may be a self-medicating behavior with multiple directly adaptive benefits to female reproduction. Electronic Publication