Comparison of Volatile Blends and Nucleotide Sequences of Two Beauveria Bassiana Isolates of Different Virulence and Repellency Towards the Termite Macrotermes Michealseni

Isolates of the fungus Beauveria bassiana have different levels of virulence and repellency against the termite Macrotermes michaelseni. In the present study, we compared the volatile profiles and gene sequences of two isolates of the fungus with different levels of virulence and repellence to the termite. Gas chromatography–mass spectrometric analyses showed quantitative and qualitative differences in the composition of volatiles of the two isolates. The repellencies of synthetic blends of 10 prominent components that mimicked the volatiles of each of the two isolates were significantly different. Subtractive bioassays showed that the repellency of each isolate was due to synergistic effects of a few constituents. As previously reported for isolates of Metarhizium anisopliae, some differences also were found in the nucleotide sequences of the two isolates of B. bassiana, suggesting a genetic basis for the observed intra-specific differences in their repellency and virulence against the termite.     

Quantitative and somatotopic mapping of neurones in the trigeminal mesencephalic nucleus and ganglion innervating teeth in monkey and baboon

Neurones of the trigeminal mesencephalic nucleus (Mes V) and ganglion innervating the periodontium of incisor, canine and molar teeth in 10 monkeys and 10 baboons were counted and mapped using the horseradish peroxidase (Hrp), retrograde axonal transport method. Periodontal afferent neurones of all these teeth were well represented in the Mes V, although the incisors had a significantly higher number of labelled neurones than the canines or molars. The primary cell bodies of the periodontal afferents were located mainly in the caudal part of the ipsilateral Mes V from the level of the inferior colliculus to the floor of the fourth ventricle in the pons. The caudal periodontal Mes V neurones may be favourably located to make collateral connections with the trigeminal motor nucleus for jaw reflexes. Incisors and canines had a large and predominantly ipsilateral representation of Hrp-labelled neurones in the ganglion. In contrast, molar representation in the ganglion was sparse and all labelled neurones supplied ipsilateral teeth. The maxillary and mandibular teeth had a somatotopic distribution within the respective maxillary (middle) and mandibular (posterolateral) compartments of the trigeminal ganglion. It is suggested that the anterior teeth with greater connections to the Mes V and the ganglion may impart greater sensory perception and be involved in jaw reflexes to ensure a good occlusal relation during mastication, while the afferent connections of the molars may initiate complex jaw reflexes during the occlusal phase of mastication.     

Feeding responses ofChilo partellus (Swinhoe) (Lepidoptera: Pyralidae) larvae to sorghum plant phenolics and their analogs

Phagostimulatory responses of third-instar larvae ofChilo Partellus to phenolic components identified in an ethyl acetate extract of the leaf whorls of 3-week-old plants ofSorghum bicolor cultivar IS 18363 were studied in no-choice bioassays. The major components in the extract were identified as 4-hydroxybenzaldehyde and 4-hydroxybenzoic acid, with 4-hydroxy-3-methoxycinnamic acid, 3,4-dihydroxycinnamic acid, and 4-hydroxycinnamic acid present in minor amounts. All but 4-hydroxycinnamic acid were stimulatory at the doses tested. 4-Hydroxybenzaldehyde was more stimulatory than other potential biogenetic analogs. Hydroxybenzoic acids generally elicited greater feeding response than cinnamic acids, and the pattern of oxygen substitution in the benzene ring was related to bioactivity.     

Chemoecological role of mammalian urine in host location by tsetse,Glossina spp. (Diptera: Glossinidae)

Trap catch size was used to investigate whetherGlossina pallidipes andG. longipennis could distinguish between the urine of the African buffalo, cattle, and waterbuck at Nguruman in southwest Kenya. NG2G traps baited with aged urine of these bovids caught significantly more of each tsetse than did the controls. The mean catch of either tsetse species in traps baited with aged urine of buffalo and cattle (tsetse hosts) and waterbuck (a nonhost) did not differ significantly. Aged urine from both tsetse hosts (buffalo and cattle) and the nonhost (waterbuck) was found to contain 4-cresol and 3-n-propylphenol in about the same ratio. However, the aged urine from other tsetse hosts (bushpig and warthog) lacked 3-n-propylphenol. Cattle urine had to be aged outside the soil to produce statistically significant increases in the trap catch ofG. pallidipes. Furthermore, patches of soil on which fresh urine of cattle was deposited, and in which it was aged, failed to effect a significant increase in the trap catch of eitherG. austeni, G. brevipalpis, orG. pallidipes as Gazi, southeast Kenya. The likelihood of tsetse either differentiating its hosts from nonhosts or locating favored hosts by the urine scent appears remote under natural conditions. It is more likely that the chemical signals critical for host location by the tsetse emanate from skin glands rather than volatilize from the urine of mammals.     

Influence of Host-Plant Surface Chemicals on the Oviposition of the Cereal Stemborer Busseola Fusca

The chemical composition of plant surfaces plays a role in selection of host plants by herbivorous insects. Once the insect reaches the plant, these cues determine host acceptance. Laboratory studies have shown that the stem borer Busseola fusca (Lepidoptera: Noctuidae), an important pest of sorghum and maize in sub-Saharan Africa, is able to differentiate between host and non-host plant species. However, no information is available on the cues used by this insect to seek and accept the host plant. Thus, the role of surface phytochemical stimuli on host selection and oviposition by B. fusca was studied in the laboratory using two host plants, sorghum, Sorghum bicolor, and maize, Zea mays, and one non-host plant, Napier grass, Pennisetum purpureum. The numbers of eggs and egg masses deposited on the three plant species were compared first under no-choice and choice conditions. In both cases, more eggs and egg masses were laid on maize and sorghum than on the non-host. Artificial surrogate stems treated with a water or chloroform surface extract of each plant were then compared with surrogate stems treated with, respectively, water or chloroform as controls, under similar conditions. Surrogate stems treated with plant water extracts did not show an increase in oviposition when compared to controls, indicating that the major compounds in these extracts, i.e., simple sugars and free amino acids, are not significantly responsible for the oviposition preference. By contrast, a chloroform extract of sorghum enhanced oviposition on the surrogate stems compared to the control, while those of maize and Napier grass showed no significant effects. Analysis of the chloroform extract of sorghum showed higher amounts of α-amyrin, ß-amyrin, and n-nonacosane compared to those of maize and Napier grass. A blend of the three chemicals significantly increased oviposition compared to the chloroform-treated control, indicating that these compounds are part of the surface chemical signature of the plant responsible for host recognition and oviposition by B. fusca.     

How geometry,size, and surface properties of tailor-made particles control the efficiency of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/hydroxyapatite nanocomposites

Bioactive calcium phosphate nanoparticles as reinforcing filler have widely been used to produce polymer nanocomposite scaffolds suitable for application in bone tissue engineering; however, no study has investigated the effect of geometry, size, and surface properties of these nanoparticles on physical and mechanical behavior of scaffolds. This study was therefore devoted to determine how the critical features of the reinforcing nanoparticles could tailor the efficiency of polymeric nanocomposites. For this, we developed fibrous nanocomposite systems in which poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, was combined with hydroxyapatite (HA) nanoparticles having different sizes, geometries, surface chemical groups, and concentrations. The results showed that critical properties could be controlled by incorporating appropriate amounts of nanoparticles with a specific geometry and surface properties. It was also seen that the tensile modulus of fibrous nanocomposite increased from 77 MPa for neat PHBV to about 161 MPa for the nanocomposites containing 15 wt% surface-modified nanoparticles with elongated morphology.     

The nature of the gregarizing signal responsible for maternal transfer of phase to the offspring in the desert locust Schistocerca gregaria

We examined aggregative behavior of hatchlings of the desert locust Schistocerca gregaria emerging from solitaria egg pods that had been incubated in sand previously used for consecutive ovipositions by gregarious females. Hatchlings derived from such eggs were significantly more gregarious than those derived from pods laid in clean sand. The gregarizing effect of the sand-associated factor originating from 3, 5, or 10 ovipositions by gregarious females increased in a dose-dependent fashion. Washing the sand with organic solvents following such ovipositions, or flushing it with nitrogen gas, led to substantial loss of its gregarizing effect, showing that the active signal is volatile and of medium polarity. The gregarizing activity of the exposed sand correlated with the presence of C-8 unsaturated ketones, (Z)-6-octen-3-one and (E,E)-3,5-octadiene-2-one and its E,Z isomer, previously shown by us to form part of the releaser pheromone system that mediates group oviposition in S. gregaria. These ketones were present in relatively large amounts in the eggs obtained from egg pods of gregarious females and were also detected in the extracts of accessory glands of gregarious females, a candidate source of the gregarization factor. It is proposed that the pheromone is secreted at the onset of oviposition. This would account for its distribution predominantly within the eggs and surrounding sand at the site of oviposition. The study sheds new light on the pheromonal mechanism associated with transgenerational transmission of gregarious characters in crowded S. gregaria populations and provides yet another case in this insect of dual releaser and primer roles played by the same pheromone blend.     

Changing Oviposition Preferences of the Desert Locust, Schistocerca gregaria, Suggest a Strong Species Predisposition for Gregarization

Field surveys at five sites within desert locust breeding habitats around Port Sudan during three successive seasons indicated that early in the rainy season the incoming solitary females oviposited predominantly in the vicinity of Heliotropium spp. (66%) and millet (32%) seedlings. Solitary nymphs also preferred to feed on these plants. Follow-up cage experiments were conducted in the field in which solitary and gregarious female locusts were presented with choices of selected desert plants and egg pods. When presented with bulrush millet, Heliotropium spp., Zygophyllum simplex, and untreated moistened sand, solitary females oviposited adjacent to the first two plants (40% and 60%, respectively). However, when offered a choice of either or both of these plants together with egg pods derived from gregarious and/or solitary insects, solitary females showed a significantly higher preference for ovipositing near gregaria egg pods than near the plants, with solitaria egg pods eliciting the least response. In contrast with solitary females and in the absence of gregaria egg pods, gregarious females preferred to oviposit in untreated moist (control) sand (74–77%) away from the plants (6–14%) or solitaria egg pods (4%). However, when present, gregaria egg pods elicited significantly more oviposition. These and previous results indicate a hierarchy of phase-dependent oviposition preferences in the desert locust and are interpreted in terms of a strong propensity of the species to exploit opportunities under appropriate conditions to facilitate congregation and the gregarization of the progeny.     

Effects of Fifth-Instar Volatiles on Sexual Maturation of Adult Desert Locust Schistocerca gregaria

The effect of the presence of gregarious fifth-instar nymphs on the sexual maturation of newly molted gregarious immature adult males and females of the desert locust S. gregaria was investigated by monitoring color changes (yellowing of body), sexual activity, aggregation–maturation pheromone titers (as measured by phenylacetonitrile levels in males), oocyte length, and oviposition time. Maturation was significantly delayed in adults that were reared together with fifth-instar nymphs (visual, tactile, and chemical signals present) with respect to all parameters measured. Male and female nymphs were equally effective in inducing this delay. Nymphs kept in an upper compartment of two-chamber cages (no visual or tactile contact possible) were similarly effective, but their feces were ineffective, suggesting the mediation of a volatile signal from the nymphs themselves. This was confirmed by examining the effect of volatiles trapped from nymphs and testing synthetic blends of previously identified nymphal aggregation pheromone components (C₆, C₈–C₁₀ aliphatic aldehydes and acids, guaiacol, and phenol) on the sexual maturation of adults. These and previous studies suggest a dual role for nymphal volatiles as nymphal aggregants and adult maturation retardants, similar to the adult volatiles that are known as adult aggregants and maturation accelerants. The results are discussed in terms of the role of the two pheromone systems in synchronizing maturation of the gregarious adults.     

Aggregation pheromone system of adult gregarious desert locust schistocerca gregaria (forskal)

Six electrophysiologically active aromatic compounds, viz., anisole, benzaldehyde, veratrole, guaiacol, phenylacetonitrile, and phenol, were identified in the volatiles of older-adult male desert locust. Young adults and females of all age groups produced none or only trace quantities of these compounds. Comparison of the aggregation responses of young and older adults to the crude, older-adult, volatile extract and different synthetic blends of the six compounds showed that the aggregation pheromone system of the adult gregarious locust consists of phenylacetonitrile, guaiacol, phenol, and benzaldehyde. Like the crude volatile extract of older males, neither the synthetic blend of the six compounds nor the adult pheromone blend evoked any significant aggregation responses from nymphs. These results confirm our previous report of sexual differentiation in the production of adult aggregation pheromone in the desert locust and of the evidence of two distinct aggregation pheromone systems in the two stages of the insect.