Prophylactic and curative effects of Bacopa monniera in gastric ulcer models.

Bacopa monniera Wettst. (BM, syn. Herpestis monniera L; Scrophulariaceae), is an Ayurvedic drug used as a rasayana. Its fresh juice was earlier reported to have significant antiulcerogenic activity. In continuation, methanolic extract of BM (BME) standardized to bacoside-A content (percentage-38.0 ± 0.9), when given in the dose of 10–50 mg/kg, twice daily for 5 days, showed dose-dependent anti-ulcerogenic on various gastric ulcer models induced by ethanol, aspirin, 2 h cold restraint stress and 4 h pylorus ligation. BME in the dose of 20 mg/kg, given for 10 days, twice daily showed healing effects against 50% acetic acid-induced gastric ulcers. Further work was done to investigate the possible mechanisms of its action by studying its effect on various mucosal offensive acid-pepsin secretion and defensive factors like mucin secretion, mucosal cell shedding, cell proliferation and antioxidant activity in rats. BME 20 mg/kg showed no effect on acid-pepsin secretion, increased mucin secretion, while it decreased cell shedding with no effect on cell proliferation. BME showed significant antioxidant effect per se and in stressed animals. Thus, the gastric prophylactic and curative effects of BME may be due to its predominant effect on mucosal defensive factors.     

Behavioral interactions between three birch aphid species and Adalia bipunctata larvae

First and fourth instars of three birch aphid species were exposed to first and fourth instars of Adalia bipunctata (L.), the most common aphid predator on silver birch, Betula pendula Roth, in northern California. Defensive behavior differed by aphid species. Euceraphis betulae (Koch) (Eb), the most successful escapee, was highly mobile and frequently walked away from coccinellid larvae. Betulaphis brevipilosa Börner (Bb), a flat, sessile species, was the least successful aphid at actively escaping from A. bipunctata larvae, but could passively escape detection when coccinellid larvae walked over nymphs and did not perceive them. Active escape behavior was much safer for aphids than passive avoidance of detection. Both instars of Eb and fourth instars of Callipterinella calliptera (Hartig) (Cc) escaped from coccinellid larvae more frequently when approached from the front, apparently using vision for pre-contact detection of A. bipunctata. These aphids avoided physical contact with larger predators more often than with smaller predators. Level of predation by A. bipunctata on these three aphid species is dependent upon types of aphid defense.

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Résumé Des larves de premier et troisième stades de 3 espèces de pucerons du bouleau: Betulaphis brevipilosa, Callipterinella calliptera et Euceraphis betulae ont été exposées aux attaques des larves du premier et du quatrième stades d'Adalia bipunctata, prédateur le plus fréquent de pucerons sur Betula pendula en Californie du Nord. Le comportement défensif dépend beaucoup de l'espèce de puceron. E. betulae, qui s'échappe avec le plus de succès, est très mobile et s'écarte fréquemment des larves agressives de coccinelles. B. brevipilosa, espèce plate, sessile, a le moins de succès dans la protection active contre les attaques des larves de A. bipunctata, mais elle peut échapper passivement à la détection des larves de coccinelles qui ne peuvent pas les discerner lorsqu'elles circulent parmi les larves de pucerons. E. betulae (aux deux stades) et C. calliptera (au quatrième) échappent le plus aux larves de coccinelles qui attaquent de front, ce qui laisse supposer que la vision permet de détecter A. bipunctata avant le contact. Le succès des larves de coccinelles varie selon les stades du puceron et de la coccinelle. Les possibilités d'obtention de niveaux de prédation élevés de ces 3 pucerons par A. bipunctata dépend du type de protection du puceron.

     

Pyrrolizidine alkaloids of probable host-plant origin in the pronotal and elytral secretion of the leaf beetle Oreina cacaliae

Oreina cacaliae (Coleoptera, Chrysomelidae) produces in its elytral and pronotal defensive secretion seneciphylline N-oxide together with small amounts of another pyrrolizidine alkaloid tentatively identified as senecionine N-oxide. This is a strong departure from the chemical composition of the defensive secretions in related species, characterized by complex mixtures of cardenolides, synthesized by the beetles from cholesterol. It is suggested that O. cacaliae sequesters the alkaloids from its host-plant, Adenostyles leucophylla. Other specimens of O. cacaliae from far distant populations feeding on Senecio nemorensis, Petasites paradoxus or P. album also produced pyrrolizidine alkaloids, but not O. speciosissima feeding on the same food plants and producing cardenolides. In addition to pyrrolizidine alkaloids, O. cacaliae secretes ethanolamine, which is also found in all the cardenolide-producing species.     

Anti-predatory autecology in the geometrid larvae of Larentia clavaria pallidata

It was suggested by Heinrich that cryptic, palatable caterpillars would adopt foliar foraging techniques which would reduce the chance of their being detected. I wished to test this hypothesis further and to determine the post-discovery tactics. I found that caterpillars of Larentia clavaria pallidat, contrary to expectations, usually rested on upper surfaces of young Althaea setosa leaves but moved to the undersides when exposed to higher light intensities. This species may be effectively concealed by older canopy leaves. These larvae usually responded to predator-like stimuli by assuming a deimatic s form but rarely dropped. Dropping may be infrequent partly because younger caterpillars could not easily relocate the foot plant. I discuss, briefly the implications of host-plant selection.     

Genetic dominance and worker interactions affect honeybee colony defense

Colonies of honeybees (Apis mellifera L.) were established thatvaried in the proportions of their workers that were of Europeanand hybrid (Africanized x European) descent. Colony defensiveresponses increased with higher proportions of hybrid workers.Colonies consisting exclusively of hybrid workers did not differin their response from "pure" Africanized colonies, suggestingthat the strong defensive behavior of Africanized workers isgenetically dominant. European workers became more defensivein colonies that also contained hybrid workers, whereas hybridworkers became less defensive in the same mixed colonies. Inmixed colonies hybrid workers were individually more likelythan Europeans to sting a leather target but not more likelyto guard the entrance.     

植物与植食性昆虫化学互作研究进展

植物与植食性昆虫之间存在着复杂的化学相互作用。一方面,当遭受植食性昆虫为害时,植物能识别植食性昆虫相关分子模式,触发早期信号事件和激素信号转导途径,并由此引起转录组与代谢组重组、直接和间接防御化合物含量升高,最后提高对植食性昆虫的抗性。另一方面,植食性昆虫也能识别植物的防御反应,并能通过分泌效应子、选贮、解毒以及降低敏感性等反防御措施抑制或适应植物的化学防御。深入剖析植物与植食性昆虫的化学互作,不仅可在理论上丰富对昆虫与植物互作关系的理解,而且可在实践上为作物害虫防控新技术的开发提供重要的理论与技术指导。     

Evolution and maintenance of microbe‐mediated protection under occasional pathogen infection

Every host is colonized by a variety of microbes, some of which can protect their hosts from pathogen infection. However, pathogen presence naturally varies over time in nature, such as in the case of seasonal epidemics. We experimentally coevolved populations of Caenorhabditis elegans worm hosts with bacteria possessing protective traits (Enterococcus faecalis), in treatments varying the infection frequency with pathogenic Staphylococcus aureus every host generation, alternating host generations, every fifth host generation, or never. We additionally investigated the effect of initial pathogen presence at the formation of the defensive symbiosis. Our results show that enhanced microbe‐mediated protection evolved during host‐protective microbe coevolution when faced with rare infections by a pathogen. Initial pathogen presence had no effect on the evolutionary outcome of microbe‐mediated protection. We also found that protection was only effective at preventing mortality during the time of pathogen infection. Overall, our results suggest that resident microbes can be a form of transgenerational immunity against rare pathogen infection.     

Insect oviposition preference between Epichloë‐symbiotic and Epichloë‐free grasses does not necessarily reflect larval performance

Variation in plant communities is likely to modulate the feeding and oviposition behavior of herbivorous insects, and plant‐associated microbes are largely ignored in this context. Here, we take into account that insects feeding on grasses commonly encounter systemic and vertically transmitted (via seeds) fungal Epichloë endophytes, which are regarded as defensive grass mutualists. Defensive mutualism is primarily attributable to alkaloids of fungal origin. To study the effects of Epichloë on insect behavior and performance, we selected wild tall fescue (Festuca arundinacea) and red fescue (Festuca rubra) as grass–endophyte models. The plants used either harbored the systemic endophyte (E+) or were endophyte‐free (E?). As a model herbivore, we selected the Coenonympha hero butterfly feeding on grasses as larvae. We examined both oviposition and feeding preferences of the herbivore as well as larval performance in relation to the presence of Epichloë endophytes in the plants. Our findings did not clearly support the female's oviposition preference to reflect the performance of her offspring. First, the preference responses depended greatly on the grass–endophyte symbiotum. In F. arundinacea, C. hero females preferred E+ individuals in oviposition‐choice tests, whereas in F. rubra, the endophytes may decrease exploitation, as both C. hero adults and larvae preferred E? grasses. Second, the endophytes had no effect on larval performance. Overall, F. arundinacea was an inferior host for C. hero larvae. However, the attraction of C. hero females to E+ may not be maladaptive if these plants constitute a favorable oviposition substrate for reasons other than the plants' nutritional quality. For example, rougher surface of E+ plant may physically facilitate the attachment of eggs, or the plants offer greater protection from natural enemies. Our results highlight the importance of considering the preference of herbivorous insects in studies involving the endophyte‐symbiotic grasses as host plants.     

Being a bright snake: Testing aposematism and mimicry in a neotropical forest

Based on color patterns and behavioral similarities, venomous coral snake Micrurus corallinus (Elapidae) may act as a model for two polymorphic species, Erythrolamprus aesculapii (Dipsadidae) and Micrurus decoratus (Elapidae). Plasticine replicas were used to investigate the aposematism of these coloration patterns and whether these species may be part of mimetic complexes in two Atlantic Forest localities in Southeast Brazil. Coral replicas were more avoided when set upon a white background, evincing that the pattern may act aposematically in contrast with light substrates. Birds attacked all four patterns equally during the mimicry experiments. Birds of prey, known to be effective in predating snakes, are quite abundant in the study areas, which may have led to this lack of avoidance. Accordingly, they predated more adult-sized replicas, which could be more dangerous. Interestingly, opossum avoided the Micrurus corallinus and Erythrolamprus aesculapii replicas that resembled the model. This suggests that opportunistic predators, as the opossum may be important selective agents in mimicry complexes.     

丛枝菌根真菌对西瓜嫁接苗生长和根系防御性酶活性的影响

在温室盆栽条件下,研究丛枝菌根(AM)真菌地表球囊霉(Glomus versiforme)对连作土壤中西瓜自根苗和嫁接苗生长、根系膜透性、丙二醛(MDA)含量和防御性酶活性的影响.结果表明： 接种AM真菌能显著增加西瓜自根苗和嫁接苗的生物量,提高根系活力,降低根系膜透性和MDA含量.接种AM真菌的自根苗地上部鲜质量、地上部干质量和根系活力分别增加了57.6%、60.0%和142.1%,而接种AM真菌的嫁接苗分别增加了26.7%、28.0%和11.0%;自根苗（C）、嫁接苗（G）、接种AM真菌自根苗（C+M）和接种AM真菌嫁接苗（G+M）的根系细胞膜透性为C>G>C+M>G+M,根系MDA含量为C>G>G+M>C+M.接种AM真菌能提高西瓜自根苗和嫁接苗根系的苯丙氨酸解氨酶(PAL)、过氧化氢酶(CAT)、过氧化物酶(POD)、几丁质酶和β 1,3 葡聚糖酶活性,而且接种AM真菌的西瓜自根苗和嫁接苗根系POD、PAL和β-1,3-葡聚糖酶活性的峰值比不接种的提前2周出现.接种AM真菌能激活西瓜自根苗和嫁接苗与抗逆性有关的防御性酶反应,使根系对逆境产生快速反应,从而提高其抗连作障碍的能力.